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#1
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Well, I guess we can argue endlessly about whether the "classic" AR-3a is
"High End". I'm the original owner of a set that's approaching 40 years old and I still love them. The 3a's are not my only AR's. I also have a set of TSW610's (12 inch woofer, 6.5 inch mid-range, & 3/4 inch titanium dome liquid cooled tweeter). The 610's are in a fairly large room, with tons of stuffed furniture and sound deadening material. 3a's are just the opposite (small room, little to no sound absorbing material). In spite of the room dynamics, the 3a's always sounded sort of "dull" compared to the 610's. That is, the 610's were just so much brighter and clearer. Now at the other end, the deep bass, 3a's were always the clear winner. For the past 6 days, I have been listening to my bi-amped AR-3a’s and I can’ t believe the difference. Bass that just GROWLS through the 12 inch woofers, high frequencies are clearer and cleaner than my TSW’s 610’s and stereo imaging that is just unbelievable. It’s hard to believe I’m listening to the same speakers. What I particularly noticed is the "punch" at low power levels. Here I’m talking about just terrific sound at 1 watt or less! I’m hearing instruments I never heard in the music before. Individual people clapping! That’s right, I can pick out individual people clapping as opposed to audience clapping. Who knows, I might just be incredibly lucky and everything fell into place, but I’d strongly recommend that AR-3a owners give this a shot. Further, it literally cost me ... nothing! The only down side is my favorite FM station that I’d listen to for hours on end (jazz only station) now sounds like crap. The 3a’s are so clear, I now hear the crude I never heard before. Oh well … I’m NOT going back. Here is what I did: 1. I always listen to my 3a’s on an old HeathKit AR1500 and I still do! Only now the Heathkit just powers the woofers, terminals 1 and 2 on the 3a’s. Natrually, you MUST remove the strap bewteen T and 2. Further, the tremble control is turned completely off. In short, the Heathkit is only producing low frequencies. (AR1500 is rated 100 watts RMS at 4 ohms) 2. I take the audio signals from Tape Output jacks. This tap is before the tone controls so it has the complete audio signal. 3. The Tape Output goes into an old Pioneer audio/video amplifier (rated at 30 watts - music power - that was in my basement collecting dust) at the VCR Audio Input. Now this amp has the bass tone control turned completely off. In short, the Pioneer is only producing higher frequencies and it is powering the tweeter and mid-range via terminals T and 1 on the 3a’s (again the strap must be removed). 4. So that leaves me with two independent volume controls. One on each amp and by adjusting these two controls I control the mix of high and low frequencies. It took me no more than 3 minutes to figure out how these two volume controls work together. 5. Now before you attempt this, you must make absolutely certain that both amps have common grounds on the speaker outputs AND those grounds MUST be connected to terminal 1 on the 3a’s. The “hot” or “red” lines go to 2 and T. Notice that the shielded audio cables from Tape Output to the VCR Input insures that ground on both amps is pegged to the approximately the same level. (It's fairly common for solid state amps to have common grounds, especially if they support standard headphone jacks. Do not .. DO NOT attempt this with tube amps!) Observations: 1. My old 30 watt amp has more than sufficient to power to drive the mid-range and tweeter. In fact, it probably has too much power, so we must be careful NOT to over drive. That is, turn the volume down whenever we change program source. 2. I did NOT open the 3a’s! The crossovers are still there, but doing little since the amps are only producing frequencies consistent with the speakers they are driving. If I ever do anything with the crossovers, I think what I’d try is putting a shunt across the coil in series with the woofer. I’d probably leave the cap in place just to insure no stray high frequencies got to the woofer. Now whether there would be any difference with the coil out is hard to say. The base is so much improved; it’s hard to believe it can get much better. Has anyone tried shunting the coil? If so, can you tell any difference? 3. There is no direct dc path between the "hot" outputs of the two amps. xover for the mid-range and tweeter provides only capactive coupling with the amp. Let me repeat the benefits on my system (of course YMMV): 1. Bass that just GROWLS - YES! the great bass of the AR3a's only got better 2. Clear/clean high frequencies 3. Great imaging and fantastic transient response 4. Lots more volume at 1 watt output (and I have absolutely no clue why this should be the case) 5. Both amps are running very cool - they are NOT being stressed at all! Before I retired the Pioneer it was my home theater amp and it normally ran so hot you could fry an egg on it. After 6 days of bi-amping it always runs just moderately warm. If you get a chance, here is an explanation of why and how bi-amping works: http://sound.westhost.com/bi-amp.htm In closing, you AR-3a owners ought to try this to see whether you can get similar results. I mean, if you gain nothing, returning to the way it was involves ... replacing the strap between T and 2. Good luck! Jerry |
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#2
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
Well, I guess we can argue endlessly about whether the "classic" AR-3a is "High End". I'm the original owner of a set that's approaching 40 years old and I still love them. The 3a's are not my only AR's. I also have a set of TSW610's (12 inch woofer, 6.5 inch mid-range, & 3/4 inch titanium dome liquid cooled tweeter). The 610's are in a fairly large room, with tons of stuffed furniture and sound deadening material. 3a's are just the opposite (small room, little to no sound absorbing material). In spite of the room dynamics, the 3a's always sounded sort of "dull" compared to the 610's. That is, the 610's were just so much brighter and clearer. Now at the other end, the deep bass, 3a's were always the clear winner. For the past 6 days, I have been listening to my bi-amped AR-3a’s and I can’ t believe the difference. Bass that just GROWLS through the 12 inch woofers, high frequencies are clearer and cleaner than my TSW’s 610’s and stereo imaging that is just unbelievable. It’s hard to believe I’m listening to the same speakers. What I particularly noticed is the "punch" at low power levels. Here I’m talking about just terrific sound at 1 watt or less! I’m hearing instruments I never heard in the music before. Individual people clapping! That’s right, I can pick out individual people clapping as opposed to audience clapping. Who knows, I might just be incredibly lucky and everything fell into place, but I’d strongly recommend that AR-3a owners give this a shot. Further, it literally cost me ... nothing! The only down side is my favorite FM station that I’d listen to for hours on end (jazz only station) now sounds like crap. The 3a’s are so clear, I now hear the crude I never heard before. Oh well … I’m NOT going back. Here is what I did: 1. I always listen to my 3a’s on an old HeathKit AR1500 and I still do! Only now the Heathkit just powers the woofers, terminals 1 and 2 on the 3a’s. Natrually, you MUST remove the strap bewteen T and 2. Further, the tremble control is turned completely off. In short, the Heathkit is only producing low frequencies. (AR1500 is rated 100 watts RMS at 4 ohms) 2. I take the audio signals from Tape Output jacks. This tap is before the tone controls so it has the complete audio signal. 3. The Tape Output goes into an old Pioneer audio/video amplifier (rated at 30 watts - music power - that was in my basement collecting dust) at the VCR Audio Input. Now this amp has the bass tone control turned completely off. In short, the Pioneer is only producing higher frequencies and it is powering the tweeter and mid-range via terminals T and 1 on the 3a’s (again the strap must be removed). 4. So that leaves me with two independent volume controls. One on each amp and by adjusting these two controls I control the mix of high and low frequencies. It took me no more than 3 minutes to figure out how these two volume controls work together. 5. Now before you attempt this, you must make absolutely certain that both amps have common grounds on the speaker outputs AND those grounds MUST be connected to terminal 1 on the 3a’s. The “hot” or “red” lines go to 2 and T. Notice that the shielded audio cables from Tape Output to the VCR Input insures that ground on both amps is pegged to the approximately the same level. (It's fairly common for solid state amps to have common grounds, especially if they support standard headphone jacks. Do not .. DO NOT attempt this with tube amps!) Observations: 1. My old 30 watt amp has more than sufficient to power to drive the mid-range and tweeter. In fact, it probably has too much power, so we must be careful NOT to over drive. That is, turn the volume down whenever we change program source. 2. I did NOT open the 3a’s! The crossovers are still there, but doing little since the amps are only producing frequencies consistent with the speakers they are driving. If I ever do anything with the crossovers, I think what I’d try is putting a shunt across the coil in series with the woofer. I’d probably leave the cap in place just to insure no stray high frequencies got to the woofer. Now whether there would be any difference with the coil out is hard to say. The base is so much improved; it’s hard to believe it can get much better. Has anyone tried shunting the coil? If so, can you tell any difference? 3. There is no direct dc path between the "hot" outputs of the two amps. xover for the mid-range and tweeter provides only capactive coupling with the amp. Let me repeat the benefits on my system (of course YMMV): 1. Bass that just GROWLS - YES! the great bass of the AR3a's only got better 2. Clear/clean high frequencies 3. Great imaging and fantastic transient response 4. Lots more volume at 1 watt output (and I have absolutely no clue why this should be the case) 5. Both amps are running very cool - they are NOT being stressed at all! Before I retired the Pioneer it was my home theater amp and it normally ran so hot you could fry an egg on it. After 6 days of bi-amping it always runs just moderately warm. If you get a chance, here is an explanation of why and how bi-amping works: http://sound.westhost.com/bi-amp.htm In closing, you AR-3a owners ought to try this to see whether you can get similar results. I mean, if you gain nothing, returning to the way it was involves ... replacing the strap between T and 2. This is a very good recipie of how *not* to do biamping. There are so many things wrong with this approach that I don't know where to start, but here are a couple of the highpoints: 1) You need to completely isolate the two amplifier outputs - with your setup the two outputs are combined in the crossover - a good way to fry an amp or start a fire. 2) Tone controls are *not* crossover filters! They are shelving filters, and completely totally at the wrong frequency. You want your crossover point to be somewhere in the 1k to 3k range. Shelving is typcally at 100 hz and 10khz, meaning that the entire range from 100 to 10k is going to *both* woofer and tweeter. 3) Much of the benefits of bi amping comes from getting the distortion-producing passive crossover components out of the signal path. You have left them in, which is actually probably a good thing in this case because you would have blown your tweeters otherwise. 4) "The crossovers are still there, but doing little since the amps are only producing frequencies consistent with the speakers they are driving." WRONG! The crossovers are still doing what they were doing before, keeping high frequencies out of the woofer and keeping low frequencies out of the tweeter. There is no way that the amps are "only producing frequencies consistent with the speakers they are driving" with only conventional shelving tone controls. If you get a chance, here is an explanation of why and how bi-amping works: http://sound.westhost.com/bi-amp.htm You should read it. What you're doing has nothing to do with the contents of this article. //Walt |
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#4
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Walt wrote(on 8/2/2006):
This is a very good recipie of how *not* to do biamping. There are so many things wrong with this approach that I don't know where to start, but here are a couple of the highpoints: 1) You need to completely isolate the two amplifier outputs - with your setup the two outputs are combined in the crossover - a good way to fry an amp or start a fire. Walt, I'm wondering why you believe the amps are "combined" in the xover? Now it’s true the AR-3a was never designed with the intent to bi-amp (like modern speakers such as JBL, Polk, Cambridge, etc). Nevertheless, a few chance coincidences allow us to bi-amp the AR-3a’s ... safely: 1. AR-3a was designed so that the woofer ALONE could be driven and to do that the woofer had to be electrically isolated from mid-range and tweeter (this is accomplished by removing the strap between terminals T and 2). 2. In the mid to late 60’s solid state amps came into existence with COMMON GROUNDS. Prior to then we had tube amps that will absolutely case the potential problems that you mentioned, Walt. 2) Tone controls are *not* crossover filters! They are shelving filters, and completely totally at the wrong frequency. You want your crossover point to be somewhere in the 1k to 3k range. Shelving is typcally at 100 hz and 10khz, meaning that the entire range from 100 to 10k is going to *both* woofer and tweeter. Well, Walt, the tone controls work (according to their specifications) at the extremes of the audio spectrum. Again my goal was to bi-amp cheaply and I had no interest in spending $'s on active filters. Plus I did NOT want to alter my beautiful AR-3a's, so I did NOT open the boxes. This means the original xovers are in place as well as the original xover frequencies. My goal in using the tone controls is twofold: 1. limit the frequency range sent to the drivers in order to minimize energy dissipation/rejection by the xovers 2. minimize IM distortion in the audio signals sent to the drivers Now, item 2 above comes directly from the web article and here is a direct quote from: http://sound.westhost.com/bi-amp.htm “Intermodulation distortion in an amplifier is a form of distortion created when two different frequencies are being amplified simultaneously. The effects of intermod are most noticeable when one of the frequencies is much lower than the other, and the high frequency signal is actually modulated by the low frequency. This is quite different from the signals simply adding as they are supposed to. The effect (musically speaking) is that the sound is muddied, and the highs lose their transparency. Individual instruments become difficult to separate as their harmonics all start to blend into a 'wall of sound' (have another look at Figure 3B - this is intermodulation distortion at its worst). By separating the low and mid+high frequencies from each other PRIOR to the power amplifiers, we reduce (to a large degree) one of the major sources of intermodulation. This is a great benefit to the music lover, since the sound instantly becomes more open and cleaner.” 3) Much of the benefits of bi amping comes from getting the distortion-producing passive crossover components out of the signal path. You have left them in, which is actually probably a good thing in this case because you would have blown your tweeters otherwise. Well … yes and NO! I agree, Walt, that the passive xovers are a potential source of distortion as well as random phase shifts. Nevertheless, we have a problem. I only have two amps and three speakers in each box. Further, unless I open the boxes, I can only isolate the woofer from the other two (mid-range and tweeter). This means I really have no choice, but to leave some of the passive xover intact, and that’s the xover that manages frequencies between mid-range and the tweeter. One further advantage of leaving this alone is that the existing xover prevents any dc path between the amps (tweeter and mid-range are capacitively coupled). So, what’s left to remove … a coil in series with the woofer and a cap across it! Again, I asked whether anyone had taken out the coil, as I wanted to know whether the differences are audible. The cap, I’d leave to prevent stray high frequencies from getting to the woofer on power-on and audio source changes. 4) "The crossovers are still there, but doing little since the amps are only producing frequencies consistent with the speakers they are driving." WRONG! The crossovers are still doing what they were doing before, keeping high frequencies out of the woofer and keeping low frequencies out of the tweeter. There is no way that the amps are "only producing frequencies consistent with the speakers they are driving" with only conventional shelving tone controls. Ok, Walt, you have a point. Certainly the tone controls do NOT create the sharp frequency cutoffs of an active xover, but with 15db attenuation I certainly am reducing significantly the amount of the energy dissipated/rejected by the xovers. Walt, would you agree with this language: "The crossovers are still there, but doing LESS work, because the amps are producing frequencies MORE consistent with the speakers they are driving." Regards, Jerry |
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#5
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
My goal in using the tone controls is twofold: 1. limit the frequency range sent to the drivers in order to minimize energy dissipation/rejection by the xovers 2. minimize IM distortion in the audio signals sent to the drivers Alternatively, you could just find an amp without excessive IM distortion. I think they exist. Now, item 2 above comes directly from the web article and here is a direct quote from: http://sound.westhost.com/bi-amp.htm "Intermodulation distortion in an amplifier is a form of distortion created when two different frequencies are being amplified simultaneously. The effects of intermod are most noticeable when one of the frequencies is much lower than the other, and the high frequency signal is actually modulated by the low frequency. This is quite different from the signals simply adding as they are supposed to. The effect (musically speaking) is that the sound is muddied, and the highs lose their transparency. Individual instruments become difficult to separate as their harmonics all start to blend into a 'wall of sound' (have another look at Figure 3B - this is intermodulation distortion at its worst). No, it's not. Figure 3B is a depiction of clipping distortion. If this guy doesn't know the difference between IMD and clipping, I'd be wary of trusting him on anything related to audio. bob |
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#6
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Walt wrote (on 8/3/2006):
From you statement "There is no direct dc path between the "hot" outputs of the two amps." This implies to me that there is a direct AC path between the outputs, which is really what matters since your amps aren't putting out DC (at least I hope they aren't). Most crossovers are this way, but the AR-3 may be different - I'd have to check the schematic to be sure. But until I was sure, I wouldn't hook two amps up to them. Hi, Walt! I agree that double checking the schematics of the xovers AND the amps is important. I did check the schematic of the AR1500 and the AR-3a xover (see below). Unfortunately, the best I could do on the Pioneer was a visual trace and some ohm meter readings. http://www.classicspeakerpages.net/a.../AR3aXorig.gif In the schematic above the dashed line between T and 2 is the strap I removed. Terminal #1 is the common ground on both amps (which are common to each other as well via the shields on the audio cables). I see no path, between the "hot outputs" of the amps to each other. But you *haven't* separated low and mid+high frequencies prior to the power amplifiers. All you've done is apply about 10 db of shelving at 100hz and 10khz. This is a far cry from a high pass / low pass combination that operates at 24db or 48db per octave. You're applying a little tone control and then running the output through a passive crossover. This is *not* biamping. Well, even you admit, Walt, that the tones controls are NOT sharp. While we may get a 15 db reduction at 100Hz there'll be a reduction of something at 500 Hz as well (possibly 3 db and maybe more). Further, today's speaker manufacturers, who supply speakers with bi-amp straps call this scheme bi-amping. See: http://www.wharfedale.co.uk/faq.php?show_faq=8 http://www.jbl.com/Home/technology/g...term=Bi-Amping Walt, I think we can agree there are degrees to bi-amping. From the very same article that you cite: The most common question I get is ... "Do I need to disconnect the passive crossover in my speakers?" The answer is ... Yes, otherwise you are not really biamping at all. This article is correct. You are not really biamping at all. Walt, would you agree with this language: "The crossovers are still there, but doing LESS work, because the amps are producing frequencies MORE consistent with the speakers they are driving." No. The crossovers are still there doing basically the same thing they were before. You've applied some voodoo to make your system more complicated, but haven't bi-amped it in any meaningful way. If you're happy with it, by all means enjoy it, but don't call it biamping, because it isn't. Walt, my approach has achieved stunning results. I can perform a before and after comparison to my other set of AR's (TSW610's) and can hear a tremendous difference. I believe the improvements are due to: 1. significantly reduced instability of the rail voltages on the mid-range/tweeter amp vs mono-amped (AR woofer at 4 ohms consumes just incredible amounts of power For example, let’s assume a low frequency voltage swing of 75 volts (peak) when a double bass string is plucked. This creates a current drain for both speakers of 38 amps!! You’d need filter condensers the size of car batteries to absorb this with zero instability.) 2. NO counter EMF from the woofer feeding directly the to mid-range/tweeter (actually this is Richard's idea) 3. reduction in IM by focusing the amps on a narrower portion of the audio spectrum These are theories, Walt, but that’s all I have right now. Well, I do have significantly improved speakers and it cost me nothing to achieve this improvement. The other thing I have and have no explanation for is that both amps are running very, very cool. Neither is being stressed and before both ran fairly hot. (Clearly they are NOT running cooler due to ambient temperature as it's hot a hell right now.) Regards, Jerry |
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#7
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
bob wrote (on 8/3/2006):
Alternatively, you could just find an amp without excessive IM distortion. I think they exist. Frankly, Bob, I believe that this particular bi-amping scheme reduces IM distortion, but I don't believe that the IM reduction causes the biggest improvement in sound. Rather, I believe the major improvements are due to: 1. significantly improved stability of the rail voltages on the mid-range/tweeter amp vs mono-amped (AR woofer at 4 ohms consumes just incredible amounts of power For example, let's assume a low frequency voltage swing of 75 volts when a double bass string is plucked. This creates a current drain for both speakers of 38 amps!! You'd need filter condensers the size of car batteries to absorb this with zero instability.) 2. NO counter EMF from the woofer feeding directly the to mid-range/tweeter (actually this is Richard's idea) Bob, if money were no object (or if the wife would understand), the ideal solution would be to have six mono blocks and an active xover. This way we'd have one independent amp feeding each speaker and those amps would only be processing frequencies consistent with the drivers. My goal, however, was to try bi-amping as cheaply and easily as possible to see whether I could tell a difference. No, it's not. Figure 3B is a depiction of clipping distortion. If this guy doesn't know the difference between IMD and clipping, I'd be wary of trusting him on anything related to audio. Well, he's claiming the clipping is really caused by mixing signals together, which are wide apart in frequency. I suppose this could happen, if you are really putting out some substantial power. That's just not my situation. My AR's are in a fairly small room and I prefer the AVERAGE power output to be under 1 watt. Nevertheless, I still believe the 4 ohm woofers stress the rail voltages due to the short term current drain. That is, while low frequencies are draining current, the high frequencies ( which cycle many, many times before the rails recover) are seeing distortion cause by the instability in the rail voltages. Horizontal bi-amping insulates the tweeter/mid-range from any distortion caused by this low frequency current drain. Further, often in jazz (my preferred music) we'll hear solid bass coming from just one speaker (caused by the microphone setup for the trio). The resulting rail instability when mono-amping impacts BOTH channels causing distortion and crosstalk. Regards, Jerry |
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#8
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
bob wrote (on 8/3/2006): Alternatively, you could just find an amp without excessive IM distortion. I think they exist. Frankly, Bob, I believe that this particular bi-amping scheme reduces IM distortion, but I don't believe that the IM reduction causes the biggest improvement in sound. Rather, I believe the major improvements are due to: 1. significantly improved stability of the rail voltages on the mid-range/tweeter amp vs mono-amped (AR woofer at 4 ohms consumes just incredible amounts of power For example, let's assume a low frequency voltage swing of 75 volts when a double bass string is plucked. This creates a current drain for both speakers of 38 amps!! You'd need filter condensers the size of car batteries to absorb this with zero instability.) Your figures are simply absurd. A voltage swing of, I assume +-75 volts implies an amplifer capable of producing 700 watts into 8 ohms. 2. NO counter EMF from the woofer feeding directly the to mid-range/tweeter (actually this is Richard's idea) And it's a bad one at that. EMF is the evil anti-christ of any number of so-called high-end pundits who have no clue of the underlying physics of what's going on. If you want to look at EMF as a signal "source" (which it is NOT), fine, but do so in at least a consistent manner with a complete understanding of what's going on. That "back EMF generator" is sitting behind a quite substantial Thevenin equivalent source impedance, and ONLY occurs proximal to the speaker's fundamental mechanical resonance. That's why you have a large peak in the impedance at that frequency. The EMF voltage is IN phase with the incoming signal and is, for all intents and purposes, essentially identical to it. Further, given that the Thevenin equivalent source impedance of backEMF signal is very large compared to the actual signal source impedance, whatever "back EMF" there is is pretty substantially attenuated by the EMF source impedance and the amplifier output impedance. In short, the notion that "counter EMF" is in any way substantively affecting the midrage and tweeter is a bunch of hooey. My goal, however, was to try bi-amping as cheaply and easily as possible to see whether I could tell a difference. That a difference exists in your scheme I don't think is at all in dispute. That the difference that results from your scheme is something you seem to like is certainly not something that's even disputable. That what you did is technically correct, that the result you got as for the reasons you claim, and such, are all very much arguable. In fact, it's quite arguable that your scheme has a number of serious problems, as others have pointed out, and that it is NOT behaving as you think it is. Among other things, your corssover scheme has veryh substantially imposed some fairly gross frequency response problems on your AR3s. I see no attempt to separate the audible results of the overall gross altered frequency response and the other effects you believe are being achieved. No, it's not. Figure 3B is a depiction of clipping distortion. If this guy doesn't know the difference between IMD and clipping, I'd be wary of trusting him on anything related to audio. Well, he's claiming the clipping is really caused by mixing signals together, which are wide apart in frequency. If this is his claim, he has not the faintest idea what he is talking about. That's just not my situation. My AR's are in a fairly small room and I prefer the AVERAGE power output to be under 1 watt. Nevertheless, I still believe the 4 ohm woofers stress the rail voltages due to the short term current drain. Then your own claims dispute one another. That is, while low frequencies are draining current, the high frequencies ( which cycle many, many times before the rails recover) are seeing distortion cause by the instability in the rail voltages. That's trivially measurable as IM distortion. Show us where this is happening and your claims gain some credence. Horizontal bi-amping insulates the tweeter/mid-range from any distortion caused by this low frequency current drain. Further, often in jazz (my preferred music) we'll hear solid bass coming from just one speaker (caused by the microphone setup for the trio). The resulting rail instability when mono-amping impacts BOTH channels causing distortion and crosstalk. That's a claim, not a fact. Measuring the power supply voltage is a trivial excercise. Instead of speculating about it with NO data whatsoever, why not, in fact, measure it? Claiming it's a problem doesn't mean it IS a problem. |
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#9
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
Walt wrote (on 8/3/2006): Walt, I'm wondering why you believe the amps are "combined" in the xover? From you statement "There is no direct dc path between the "hot" outputs of the two amps." This implies to me that there is a direct AC path between the outputs... I'd have to check the schematic to be sure. But until I was sure, I wouldn't hook two amps up to them. I agree that double checking the schematics of the xovers AND the amps is important. http://www.classicspeakerpages.net/a.../AR3aXorig.gif Yes, removing the strap isolates the output of the two amplifiers. That's clear from the schematic. This means that what you are doing is not actually dangerous. That's good news. So, scratch my criticism of combining the two amplifier outputs - that's apparently not going on here. Further, today's speaker manufacturers, who supply speakers with bi-amp straps call this scheme bi-amping. See: http://www.wharfedale.co.uk/faq.php?show_faq=8 http://www.jbl.com/Home/technology/g...term=Bi-Amping Walt, I think we can agree there are degrees to bi-amping. "Biamping" has degenerated into a marketing buzzword and is used in situations where it is really not applicable at all. For instance, Wharfdale describes using separate mono amps to drive left and right speakers as a form of biamping. I consider this to be an abuse of language to fool neophytes into thinking they've got something they haven't. Using this line of reasoning we can call a garden variety stereo receiver "biamping" because it has two power amplifiers inside it. But saying it doesn't make it so. What you're doing is sometimes euphamistically called "passive biamping" where separate amps are used to drive high and low via the passive crossovers inside the speaker cabinet. This is not "real" biamping (which involves an active crossover), but it does involve two amps so manufacturers can tout it as biamping without explicitly lying. But it is misleading. Your favorite biamping resourse (http://sound.westhost.com/bi-amp.htm) has this to say about it: "Passive biamping (where two amplifiers are used in a bi-wiring connection) is, IMHO, a waste of money." Walt, my approach has achieved stunning results. If you say so. Enjoy. //Walt |
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#10
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning
John Stone wrote:
In my opinion, the best thing to do is to just get a single amp that's capable of properly driving the speakers in the first place. The most intelligent sentence in this entire thread. //Walt |
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#11
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
bob wrote (on 8/3/2006): Alternatively, you could just find an amp without excessive IM distortion. I think they exist. Frankly, Bob, I believe that this particular bi-amping scheme reduces IM distortion, but I don't believe that the IM reduction causes the biggest improvement in sound. If by "this particular bi-amping scheme" you mean with an electronic crossover ahead of the two amps, then yes, it will reduce IMD. But if IMD is already below audible levels, it will have no impact on what you hear. snip Bob, if money were no object (or if the wife would understand), the ideal solution would be to have six mono blocks and an active xover. This way we'd have one independent amp feeding each speaker and those amps would only be processing frequencies consistent with the drivers. Sure, but the primary advantage (and maybe the only advantage) to this set-up over a single amp (powerful enough to drive the speaker, of course) derives from the use of an electronic crossover in place of the passive crossovers inside the speaker. And how big an advantage that is depends largely on how bad the passive crossovers are. snip No, it's not. Figure 3B is a depiction of clipping distortion. If this guy doesn't know the difference between IMD and clipping, I'd be wary of trusting him on anything related to audio. Well, he's claiming the clipping is really caused by mixing signals together, which are wide apart in frequency. I suppose this could happen, if you are really putting out some substantial power. Well, he's muddling up two very simple and distinct concepts, which makes me wonder whether he really knows what he's talking about. bob |
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#12
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
Well, I guess we can argue endlessly about whether the "classic" AR-3a is "High End". I'm the original owner of a set that's approaching 40 years old and I still love them. The 3a's are not my only AR's. I also have a set of TSW610's (12 inch woofer, 6.5 inch mid-range, & 3/4 inch titanium dome liquid cooled tweeter). The 610's are in a fairly large room, with tons of stuffed furniture and sound deadening material. 3a's are just the opposite (small room, little to no sound absorbing material). In spite of the room dynamics, the 3a's always sounded sort of "dull" compared to the 610's. That is, the 610's were just so much brighter and clearer. Now at the other end, the deep bass, 3a's were always the clear winner. For the past 6 days, I have been listening to my bi-amped AR-3a’s and I can’ t believe the difference. Bass that just GROWLS through the 12 inch woofers, high frequencies are clearer and cleaner than my TSW’s 610’s and stereo imaging that is just unbelievable. It’s hard to believe I’m listening to the same speakers. What I particularly noticed is the "punch" at low power levels. Here I’m talking about just terrific sound at 1 watt or less! I’m hearing instruments I never heard in the music before. Individual people clapping! That’s right, I can pick out individual people clapping as opposed to audience clapping. Who knows, I might just be incredibly lucky and everything fell into place, but I’d strongly recommend that AR-3a owners give this a shot. Further, it literally cost me ... nothing! The only down side is my favorite FM station that I’d listen to for hours on end (jazz only station) now sounds like crap. The 3a’s are so clear, I now hear the crude I never heard before. Oh well … I’m NOT going back. Here is what I did: 1. I always listen to my 3a’s on an old HeathKit AR1500 and I still do! Only now the Heathkit just powers the woofers, terminals 1 and 2 on the 3a’s. Natrually, you MUST remove the strap bewteen T and 2. Further, the tremble control is turned completely off. In short, the Heathkit is only producing low frequencies. (AR1500 is rated 100 watts RMS at 4 ohms) 2. I take the audio signals from Tape Output jacks. This tap is before the tone controls so it has the complete audio signal. 3. The Tape Output goes into an old Pioneer audio/video amplifier (rated at 30 watts - music power - that was in my basement collecting dust) at the VCR Audio Input. Now this amp has the bass tone control turned completely off. In short, the Pioneer is only producing higher frequencies and it is powering the tweeter and mid-range via terminals T and 1 on the 3a’s (again the strap must be removed). 4. So that leaves me with two independent volume controls. One on each amp and by adjusting these two controls I control the mix of high and low frequencies. It took me no more than 3 minutes to figure out how these two volume controls work together. 5. Now before you attempt this, you must make absolutely certain that both amps have common grounds on the speaker outputs AND those grounds MUST be connected to terminal 1 on the 3a’s. The “hot” or “red” lines go to 2 and T. Notice that the shielded audio cables from Tape Output to the VCR Input insures that ground on both amps is pegged to the approximately the same level. (It's fairly common for solid state amps to have common grounds, especially if they support standard headphone jacks. Do not .. DO NOT attempt this with tube amps!) Observations: 1. My old 30 watt amp has more than sufficient to power to drive the mid-range and tweeter. In fact, it probably has too much power, so we must be careful NOT to over drive. That is, turn the volume down whenever we change program source. 2. I did NOT open the 3a’s! The crossovers are still there, but doing little since the amps are only producing frequencies consistent with the speakers they are driving. If I ever do anything with the crossovers, I think what I’d try is putting a shunt across the coil in series with the woofer. I’d probably leave the cap in place just to insure no stray high frequencies got to the woofer. Now whether there would be any difference with the coil out is hard to say. The base is so much improved; it’s hard to believe it can get much better. Has anyone tried shunting the coil? If so, can you tell any difference? 3. There is no direct dc path between the "hot" outputs of the two amps. xover for the mid-range and tweeter provides only capactive coupling with the amp. Let me repeat the benefits on my system (of course YMMV): 1. Bass that just GROWLS - YES! the great bass of the AR3a's only got better 2. Clear/clean high frequencies 3. Great imaging and fantastic transient response 4. Lots more volume at 1 watt output (and I have absolutely no clue why this should be the case) 5. Both amps are running very cool - they are NOT being stressed at all! Before I retired the Pioneer it was my home theater amp and it normally ran so hot you could fry an egg on it. After 6 days of bi-amping it always runs just moderately warm. If you get a chance, here is an explanation of why and how bi-amping works: http://sound.westhost.com/bi-amp.htm In closing, you AR-3a owners ought to try this to see whether you can get similar results. I mean, if you gain nothing, returning to the way it was involves ... replacing the strap between T and 2. Good luck! Jerry Ok --- I did not read each and every counter post to the original thread, but... IF the tone controls work entirely "out of band" (ie. the treble control ABOVE the LP filter for the woofer, etc...) then there is certainly benefit to be had by this method OVER the original single AR1500 running the AR3 speakers. The AR1500 was not a particularly great amplifier to begin with, and no doubt, getting 20-30dB of HF infomation out of it will not hurt. One is also attenuating the "out of band" energy considerably. Which if it happens to closely correspond to the turn over freqs for the AR3s xover, is likely to be a benefit as well. It is probably a better idea to get some nice used modern speakers (many of them have superior characteristics to the old AR3...) and a modern amplifier(s) be they tube or solid state, used can be fairly inexpensive. Buying used can keep things reasonable. I'd encourage you to continue to experiment and try new things, and new gear. Notwithstanding some of the "wet blanket" comments in the thread, the main idea is to experiment, study, learn, try new things, improve in all respects. None of the vernerable old gear you are having fun with, and finding ways to "improve" is within an order of magnitude of the objectively measured specs of the gear available today. The term "hopelessly outdated" does come to mind. That doesn't mean it can't be fun to listen to! Consier some of the many many DIY & kit offerings out there in both amps and speakers... in the case of amps, much has been learned about amps since those AR1500s were designed, and in speakers the drivers themselves are considerably improved overall... Bottom line, is that there are likely better ways to "skin the cat." I'd suggest checking some of them out? Take your rekindled enthusiasm and turn it in those other directions! _-_-bear |
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#13
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
wrote on 8/4/2006:
Your figures are simply absurd. A voltage swing of, I assume +-75 volts implies an amplifer capable of producing 700 watts into 8 ohms. Oh, really?? I have a 20 year old amp with +/- 72 volt rails (150 watts/channel) and several folks here have indicatied that they have modern amps with rails of +/- 100 volts. My example was way below clipping on those amps. So what's absurb? Perhaps we must make all those folks with amps of 100 volt rails or more turn them in?? 2. NO counter EMF from the woofer feeding directly the to mid-range/tweeter (actually this is Richard's idea) And it's a bad one at that. EMF is the evil anti-christ of any number of so-called high-end pundits who have no clue of the underlying physics of what's going on. If you want to look at EMF as a signal "source" (which it is NOT), fine, but do so in at least a consistent manner with a complete understanding of what's going on. That "back EMF generator" is sitting behind a quite substantial Thevenin equivalent source impedance, and ONLY occurs proximal to the speaker's fundamental mechanical resonance. That's why you have a large peak in the impedance at that frequency. The EMF voltage is IN phase with the incoming signal and is, for all intents and purposes, essentially identical to it. Further, given that the Thevenin equivalent source impedance of backEMF signal is very large compared to the actual signal source impedance, whatever "back EMF" there is is pretty substantially attenuated by the EMF source impedance and the amplifier output impedance. In short, the notion that "counter EMF" is in any way substantively affecting the midrage and tweeter is a bunch of hooey. Well, I admit that I don't understand much about the back EMF caused by the woofer motor. The whole "theory" on counter EMF came from Richard and I'll leave him to defend it. All I'll say is the counter EMF at the motor frequency would, of course, be invisible to the mid-range and tweeters due to the xover. The bigger issue is does the motor generate harmonics of is base frequency? If so, those harmonics would flow freely to the mid-range and tweeter, because the xover would offer that as the "path of least resistance". Like you state, there is simply no way those harmonics will find their way back into the amp. My goal, however, was to try bi-amping as cheaply and easily as possible to see whether I could tell a difference. That a difference exists in your scheme I don't think is at all in dispute. That the difference that results from your scheme is something you seem to like is certainly not something that's even disputable. That what you did is technically correct, that the result you got as for the reasons you claim, and such, are all very much arguable. In fact, it's quite arguable that your scheme has a number of serious problems, as others have pointed out, and that it is NOT behaving as you think it is. Among other things, your corssover scheme has veryh substantially imposed some fairly gross frequency response problems on your AR3s. I see no attempt to separate the audible results of the overall gross altered frequency response and the other effects you believe are being achieved. I don't understand how you or anyone can say I've alter the frequency response of the AR-3a's. In fact, I've run a number of tests and in every single test the original xovers are doing exactly what they are supposed to do. That is, they allow only the correct frequencies to the drivers. If only the correct frequencies are getting to the drivers, how is it that I've made the drivers more or less sensitive?? Now, perhaps we are talking about different things. My definintion of frequency response is power into the speakers and sound produced (output if you will) over the complete audio spectrum. I seriously doubt I've changed the frequency response of the AR-3a's, which I never opened. The very fact that the original xovers are intact and WORKING properly suggests just the opposite. No, it's not. Figure 3B is a depiction of clipping distortion. If this guy doesn't know the difference between IMD and clipping, I'd be wary of trusting him on anything related to audio. Well, he's claiming the clipping is really caused by mixing signals together, which are wide apart in frequency. If this is his claim, he has not the faintest idea what he is talking about. That's just not my situation. My AR's are in a fairly small room and I prefer the AVERAGE power output to be under 1 watt. Nevertheless, I still believe the 4 ohm woofers stress the rail voltages due to the short term current drain. Then your own claims dispute one another. That is, while low frequencies are draining current, the high frequencies ( which cycle many, many times before the rails recover) are seeing distortion cause by the instability in the rail voltages. That's trivially measurable as IM distortion. Show us where this is happening and your claims gain some credence. I don't have any proof, it's only a theory. I do, however, have some speaker companies that address this issue: http://www.wharfedale.co.uk/faq.php?show_faq=8 http://www.jbl.com/Home/technology/g...term=Bi-Amping JBL evens states that the "norm" is to leave the passive xovers intact. Horizontal bi-amping insulates the tweeter/mid-range from any distortion caused by this low frequency current drain. Further, often in jazz (my preferred music) we'll hear solid bass coming from just one speaker (caused by the microphone setup for the trio). The resulting rail instability when mono-amping impacts BOTH channels causing distortion and crosstalk. That's a claim, not a fact. Measuring the power supply voltage is a trivial excercise. Instead of speculating about it with NO data whatsoever, why not, in fact, measure it? Claiming it's a problem doesn't mean it IS a problem. You mean put it on a DC scope with a sweep frequency in the 40 to 50 Hz range. Unfortunately, all I have is an old AC scope. Even with a DC scope I'm not sure we could see such short duration "instability". How would you measure it? As I've said a number of times, the improvements I've experienced may all be "dumb luck", such as: 1. my three drivers are in better phase with each other than before (the twos amps are adjusting phase to my advantage) 2. that "old" cheap Pioneer amp is actually doing a better job on the high frequencies than my AR1500 (now, I'll be the first to admit this doesn't seem right, but who knows?) When all is said and done, I'd really like to see other AR-3a owners try this "cheap, non-invasive" scheme and tell us what you hear. I'm fortunate in that I can do a "before" and "after" comparison using a second set of AR's as a reference. Regards, Jerry |
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#14
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
bob wrote (on 8/4/2006):
Bob, if money were no object (or if the wife would understand), the ideal solution would be to have six mono blocks and an active xover. This way we'd have one independent amp feeding each speaker and those amps would only be processing frequencies consistent with the drivers. Sure, but the primary advantage (and maybe the only advantage) to this set-up over a single amp (powerful enough to drive the speaker, of course) derives from the use of an electronic crossover in place of the passive crossovers inside the speaker. And how big an advantage that is depends largely on how bad the passive crossovers are. Well, Bob, Wharfedale doesn't agree with you: http://www.wharfedale.co.uk/faq.php?show_faq=8 Neither does JBL: http://www.jbl.com/Home/technology/g...term=Bi-Amping According to JBL the "norm" is to leave the passive xovers in place. Then Polk warns that "removal of the internal passive xover ... unless you REALLY know what you're doing, you may get worse sound than you started with." http://www.polkaudio.com/homeaudio/p...ing/?helpid=53 Lastly, I'm experiencing terrific improvements in imaging, transient response and high frequency definition/ clarity and my xovers are intact. Bob, it has to more than just the xovers. The stress on the amps caused by the woofers just has to playing some role. No, it's not. Figure 3B is a depiction of clipping distortion. If this guy doesn't know the difference between IMD and clipping, I'd be wary of trusting him on anything related to audio. Well, he's claiming the clipping is really caused by mixing signals together, which are wide apart in frequency. I suppose this could happen, if you are really putting out some substantial power. Well, he's muddling up two very simple and distinct concepts, which makes me wonder whether he really knows what he's talking about. bob Bob, you're probably right that the guy is embellishing a little here. |
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#15
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning
"Walt" wrote in message
... John Stone wrote: In my opinion, the best thing to do is to just get a single amp that's capable of properly driving the speakers in the first place. The most intelligent sentence in this entire thread. //Walt Well and what is that single amp?? It is 500 watts per channel and each channel has it's own transformer and isolated power supply? Funny how the professionals go with bi-amping and event the speaker manufacuturers admit that it helps: http://www.wharfedale.co.uk/faq.php?show_faq=8 http://www.jbl.com/Home/technology/g...term=Bi-Amping http://www.polkaudio.com/homeaudio/p...ing/?helpid=53 Regards, Jerry |
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#16
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
BEAR wrote (on 8/4/2006):
Ok --- I did not read each and every counter post to the original thread, but... IF the tone controls work entirely "out of band" (ie. the treble control ABOVE the LP filter for the woofer, etc...) then there is certainly benefit to be had by this method OVER the original single AR1500 running the AR3 speakers. The AR1500 was not a particularly great amplifier to begin with, and no doubt, getting 20-30dB of HF infomation out of it will not hurt. One is also attenuating the "out of band" energy considerably. Which if it happens to closely correspond to the turn over freqs for the AR3s xover, is likely to be a benefit as well. Hi, Bear! I suspect you are right about the AR1500. That is, the amp is NOT so great. Now the FM on the other hand is fantastic. Those old Heath people knew how to design world classs radios. I know this sounds strange, but I prefer my local PBS jazz FM station to the satellite stations. The music just seems to possess qualities (like transient response and imaging) superior to satellite. Now, commercial stations seem to lack the "punch" that I get on the PBS stations and I have no idea why that's the case. It is probably a better idea to get some nice used modern speakers (many of them have superior characteristics to the old AR3...) and a modern amplifier(s) be they tube or solid state, used can be fairly inexpensive. Buying used can keep things reasonable. Well, Bear, here is where you'll get resistance. Some of us AR folks have grown accustomed to the "tight", "well defined" bass that only can be achieved via acoustic suspension. I own ported speakers (JBL's) and they're OK, but given a choice, I'll listen to the AR's. Prior to bi-amping, I listened to the ported speakers far more frequently, because they had such superior imaging, transient response and clarity. The JBL's have no "edge" since I set up the bi-amp. Further, the great bass of the AR's .... only got better! I'll probably start a war here, but Bear do you realize how hard it is to find acoustic suspension speakers these days? The big three, AR, KLH and Advent no longer made AS speakers!! My favorite music is jazz and in jazz there is a ton of music with double bass. The AR's just GROWL on those really low notes. There is an outfit that makes some AS sub-woofers. I think it's called Velodyne, but man are they expensive! To a certain extent, I have turned the woofers in my AR-3a's into "passive subwoofers". I'd encourage you to continue to experiment and try new things, and new gear. Notwithstanding some of the "wet blanket" comments in the thread, the main idea is to experiment, study, learn, try new things, improve in all respects. None of the vernerable old gear you are having fun with, and finding ways to "improve" is within an order of magnitude of the objectively measured specs of the gear available today. The term "hopelessly outdated" does come to mind. That doesn't mean it can't be fun to listen to! Consier some of the many many DIY & kit offerings out there in both amps and speakers... in the case of amps, much has been learned about amps since those AR1500s were designed, and in speakers the drivers themselves are considerably improved overall... Bottom line, is that there are likely better ways to "skin the cat." I'd suggest checking some of them out? Take your rekindled enthusiasm and turn it in those other directions! _-_-bear Well said, Bear!!! I tried to talk my wife into a new set of speakers. Well 20 YEARS newer than mine - see: http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA:IT&ih=002 She told me that if I move these into our house, that I should plan on moving out! She said they look like coffins! Trouble is all the stuff I like has a very, very low WAF. Oh well .... Regards, Jerry |
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#17
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Walt wrote:
Jerry wrote: Walt wrote (on 8/3/2006): Walt, I'm wondering why you believe the amps are "combined" in the xover? From you statement "There is no direct dc path between the "hot" outputs of the two amps." This implies to me that there is a direct AC path between the outputs... I'd have to check the schematic to be sure. But until I was sure, I wouldn't hook two amps up to them. I agree that double checking the schematics of the xovers AND the amps is important. http://www.classicspeakerpages.net/a.../AR3aXorig.gif Yes, removing the strap isolates the output of the two amplifiers. That's clear from the schematic. This means that what you are doing is not actually dangerous. That's good news. So, scratch my criticism of combining the two amplifier outputs - that's apparently not going on here. Further, today's speaker manufacturers, who supply speakers with bi-amp straps call this scheme bi-amping. See: http://www.wharfedale.co.uk/faq.php?show_faq=8 http://www.jbl.com/Home/technology/g...term=Bi-Amping Walt, I think we can agree there are degrees to bi-amping. "Biamping" has degenerated into a marketing buzzword and is used in situations where it is really not applicable at all. For instance, Wharfdale describes using separate mono amps to drive left and right speakers as a form of biamping. I consider this to be an abuse of language to fool neophytes into thinking they've got something they haven't. Using this line of reasoning we can call a garden variety stereo receiver "biamping" because it has two power amplifiers inside it. But saying it doesn't make it so. What you're doing is sometimes euphamistically called "passive biamping" where separate amps are used to drive high and low via the passive crossovers inside the speaker cabinet. This is not "real" biamping (which involves an active crossover), but it does involve two amps so manufacturers can tout it as biamping without explicitly lying. But it is misleading. Your favorite biamping resourse (http://sound.westhost.com/bi-amp.htm) has this to say about it: "Passive biamping (where two amplifiers are used in a bi-wiring connection) is, IMHO, a waste of money." Walt, my approach has achieved stunning results. If you say so. Enjoy. //Walt If I may be allowed a little pedantry, "real" biamping, as described above i.e. where the crossover is done electronically at signal level, is properly described as Active Operation. The term "biamping" is used for "passive biamping" i.e. where the crossover is done at 'speaker level, and is, as Walt has quoted, a waste of money and effort. If this convention were to be followed, it would remove all ambiguity. S. |
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#18
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
bob wrote (on 8/4/2006): Bob, if money were no object (or if the wife would understand), the ideal solution would be to have six mono blocks and an active xover. This way we'd have one independent amp feeding each speaker and those amps would only be processing frequencies consistent with the drivers. Sure, but the primary advantage (and maybe the only advantage) to this set-up over a single amp (powerful enough to drive the speaker, of course) derives from the use of an electronic crossover in place of the passive crossovers inside the speaker. And how big an advantage that is depends largely on how bad the passive crossovers are. Well, Bob, Wharfedale doesn't agree with you: http://www.wharfedale.co.uk/faq.php?show_faq=8 Neither does JBL: http://www.jbl.com/Home/technology/g...term=Bi-Amping According to JBL the "norm" is to leave the passive xovers in place. Then Polk warns that "removal of the internal passive xover ... unless you REALLY know what you're doing, you may get worse sound than you started with." http://www.polkaudio.com/homeaudio/p...ing/?helpid=53 Lastly, I'm experiencing terrific improvements in imaging, transient response and high frequency definition/ clarity and my xovers are intact. Bob, it has to more than just the xovers. The stress on the amps caused by the woofers just has to playing some role. Normally, I would suggest that all instances of biamping with passive crossovers is a waste of time, as it *can't* make a difference with normal modern high-current amplifiers and loudspeakers with a *normal* impedance characteristic. However, here, I think, we have the example that proves the rule. Firstly, the loudspeakers in question have an extreme impedance characteristic that is a severe load for an amplifier. Secondly, the original amplifier being used is not a modern high-current output amplifier, but a vintage unit with limited current capability. Consequently, passive biamping *in this case* can be beneficial, as separating the lf and hf currents will lessen the load on the power amplifiers being used. If this works for the OP fine, but I think he would get considerably better results with a single modern high-current capable amplifier and normal single wiring using thick low-resistance cable. Measurements can verify this, if the OP is sufficiently interested and/or has the equipment to do the measurements. S. |
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#19
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning
Jerry wrote:
"Walt" wrote in message ... John Stone wrote: In my opinion, the best thing to do is to just get a single amp that's capable of properly driving the speakers in the first place. The most intelligent sentence in this entire thread. //Walt Well and what is that single amp?? It is 500 watts per channel and each channel has it's own transformer and isolated power supply? Funny how the professionals go with bi-amping and event the speaker manufacuturers admit that it helps: Actually no, professionals go with Active operation, not biamping. Please see my earlier post for the difference, and there is a considerable difference, one works, and the other doesn't. As to why 'speaker manufacturers talk about biamping, the cynic in me suspects this is fashion and a way of helping their dealers sell more power amplifiers. If you do the sums, a single modern high-current output amplifier won't benefit at all from passive biamping. Power is not the issue, current is. Modern solid-state amplifiers are generally capable of providing much more current than is strictly required by their 8 ohm continuous power rating, and consequently can drive even difficult loads. S. |
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#20
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
bob wrote (on 8/4/2006): Sure, but the primary advantage (and maybe the only advantage) to this set-up over a single amp (powerful enough to drive the speaker, of course) derives from the use of an electronic crossover in place of the passive crossovers inside the speaker. And how big an advantage that is depends largely on how bad the passive crossovers are. Well, Bob, Wharfedale doesn't agree with you: http://www.wharfedale.co.uk/faq.php?show_faq=8 Nothing here that disagrees with what I said. They're talking about passive bi-amping as a means of increasing available power. If you need more power, bi-amping is one way to get it, but it isn't necessarily any better than just buying the right amp in the first place. Neither does JBL: http://www.jbl.com/Home/technology/g...term=Bi-Amping According to JBL the "norm" is to leave the passive xovers in place. Again, nothing here disagrees with my statement. Of course passive bi-amping is the norm. That's because most consumers wouldn't begin to know how to do it any other way. Then Polk warns that "removal of the internal passive xover ... unless you REALLY know what you're doing, you may get worse sound than you started with." http://www.polkaudio.com/homeaudio/p...ing/?helpid=53 You missed the part where Polk called your approach "half-baked." Lastly, I'm experiencing terrific improvements in imaging, transient response and high frequency definition/ clarity and my xovers are intact. Hey, if you're happy, I'm happy. But I wouldn't recommend yours as a good general approach to happiness. It seems to depend too much on your own sense of efficacy. Bob, it has to more than just the xovers. The stress on the amps caused by the woofers just has to playing some role. Why? Because science just has to work the way you want it to? Dream on, my friend. If you've got a lousy amp that isn't capable of driving your speaker, then taking some of the load off is a good idea. But the premise of everything here is that you have a lousy amp to start with. bob |
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#21
Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
wrote on 8/4/2006: Your figures are simply absurd. A voltage swing of, I assume +-75 volts implies an amplifer capable of producing 700 watts into 8 ohms. Sorry, that was 4 ohms Oh, really?? Oh really, yes. Since: P = E^2/R where P is continuous watts, E is RMS voltage, and R is load resistance, and since a peak voltage of 75 volts, minus a couple of colts for junction drops giving you your 72 volts peak, is equal to an RMS voltage of a sine wave of 72 * 0.707 = 51 volts RMS, then, it follows: P = 51^2 / 4 P = 2601 / 4 P = 650 watts continuous Even given an 8 ohm load, that's still 325 watts continuous. I have a 20 year old amp with +/- 72 volt rails (150 watts/ channel) It might be 150 watts per channel, but iot don't have a +- 72 volt rail when it's doing it. and several folks here have indicatied that they have modern amps with rails of +/- 100 volts. My example was way below clipping on those amps. Simple math states otherwise, despite what you think other people may or may not have. So what's absurb? Perhaps we must make all those folks with amps of 100 volt rails or more turn them in?? What's absurd is your statements regarding rail voltage power and more. 2. NO counter EMF from the woofer feeding directly the to mid-range/tweeter (actually this is Richard's idea) And it's a bad one at that. EMF is the evil anti-christ of any number of so-called high-end pundits who have no clue of the underlying physics of what's going on. In short, the notion that "counter EMF" is in any way substantively affecting the midrage and tweeter is a bunch of hooey. Well, I admit that I don't understand much about the back EMF caused by the woofer motor. The whole "theory" on counter EMF came from Richard and I'll leave him to defend it. No, the whole theory on back EMF has been well understood in the physics and engineering realm long before "Richard" came a long and started spouting nonsense. All I'll say is the counter EMF at the motor frequency would, of course, be invisible to the mid-range and tweeters due to the xover. No, it's invisible to to woofer and tweeter because of the effective motor source inmpedance and the very low effective load impedance, and at the frequency at which it is greatest, it is, by definition, precisely in phase with the incoming signal. The bigger issue is does the motor generate harmonics of is base frequency? If it does, then the whole issue of attenuation due to the high source impedance and low sink impedance still holds, only more so for several reasons: 1. The effective source impedance is higher at higher frequencies, thus the attenuation is greater, 2. The levels of these harmonics are substantially below the levels of the original signals to begin with, thus you have smaller signals being attenuation more. If so, those harmonics would flow freely to the mid- range and tweeter, because the xover would offer that as the "path of least resistance". The path of least resistance is the output impedance of the amplifier, and the shunt capacitance of the woofer crossover, all a far lower than the effective input impedance of the drivers, with or without crossovers. Like you state, there is simply no way those harmonics will find their way back into the amp. No, I am stating that due to the extremely low effective impedance presented by the amplifier, there's no way they'll find their way to the other drivers. In fact, it's quite arguable that your scheme has a number of serious problems, as others have pointed out, and that it is NOT behaving as you think it is. Among other things, your corssover scheme has veryh substantially imposed some fairly gross frequency response problems on your AR3s. I see no attempt to separate the audible results of the overall gross altered frequency response and the other effects you believe are being achieved. I don't understand how you or anyone can say I've alter the frequency response of the AR-3a's. You have grossly changed the balance of the signal your feeding to the speaker. If you don't understand how, you need step back and carefully analyse what you've done. In fact, I've run a number of tests What "tests?" and in every single test the original xovers are doing exactly what they are supposed to do. That is, they allow only the correct frequencies to the drivers. Now, crossovers DO NOT do that, especially the old AR3a crossovers. These and the vast majority of passive and analog active crossovers GRADUALLY attenuate the out-of-band signals going to the drivers. The do NOT abruptly prevent frequecnies outside the passband from reaching the drivers. Thus, any chnage you make in the response being fed to the speaker outside the passband WILL affect the integrated response of the system, like it or not. If only the correct frequencies are getting to the drivers, how is it that I've made the drivers more or less sensitive?? You've changed the response being fed to them. Now, perhaps we are talking about different things. My definintion of frequency response is power into the speakers and sound produced (output if you will) over the complete audio spectrum. There already is in place a working definition of frequency response that's been widely accepted by the physics and audio community as a whole for decades How about using that one instead? That definition is given a inpu signal to a system whose voltage is constant and independent of frequency, what is the output of that system as a function of frequency? In your case, your scheme HAS change the frequency response of the signal, it is no longer constant, thus you HAVE changed the response of the system. I seriously doubt I've changed the frequency response of the AR-3a's, which I never opened. The very fact that the original xovers are intact and WORKING properly suggests just the opposite. Try the following: Take any audio system and change the position of the tone controls. You have obviously NOT altered the speakers in any way. Now, a question: because you have not changed the speakers in any way, is it therefore true, and this is your assertion, in its essence, that the frequency response of the system is unchanged? (a secret hint: you HAVE changed the frequency response of the system). That's trivially measurable as IM distortion. Show us where this is happening and your claims gain some credence. I don't have any proof, it's only a theory. I do, however, have some speaker companies that address this issue: You don't even have any data. You claim "tests" but show nothing. JBL evens states that the "norm" is to leave the passive xovers intact. SO what? THat's completely irrelevant to the fact that you have substantially altered the response of the system. That's a claim, not a fact. Measuring the power supply voltage is a trivial excercise. Instead of speculating about it with NO data whatsoever, why not, in fact, measure it? Claiming it's a problem doesn't mean it IS a problem. You mean put it on a DC scope with a sweep frequency in the 40 to 50 Hz range. Unfortunately, all I have is an old AC scope. Even with a DC scope I'm not sure we could see such short duration "instability". How would you measure it? Any number of ways. That you have an AC scope is irrelevant to the problem: if the rails are changing voltage, guess what? That's AC! Measure it. Consider hooking the amplifier output to the X channel and the supply rail to the Y channel, with about a 1:10 or greater difference in the gain between the two. Now watch the scope. And even then, that doesn't include the fact that MOST amplifiers have a pretty good power supply rejection ratio. If you assertion is true, then it should exhibit itself as increased intermodulation distortion. Simple as that. But,, look, YOUR the one making the assertions here. 1. my three drivers are in better phase with each other than before (the twos amps are adjusting phase to my advantage) That's not only unlikely, it's almost ludicrous. Not only WHY would such be true, but HOW would it be true? 2. that "old" cheap Pioneer amp is actually doing a better job on the high frequencies than my AR1500 (now, I'll be the first to admit this doesn't seem right, but who knows?) Uhm, those who have actually spent years and decades researching and measuring these sorts of things? Try a third explanation: 3. You've altered the overal response of the system in such a way that, at the moment, you like it. Over the last 30 years or so having seen these sorts of tweaks and "special" modifications like this one), almost without exception, #3 has been the dominant explanantion. |
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#22
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Bi-amping the AR-3a cheaply and non-invasively stunning
Jerry,
In spite of my own better judgment I'm going to give this discussion one last go: What I believe is frustrating me and many other here is that you are making claims that you simply can't back up. And that you refuse to acknowledge people who have a whole lot more experience at this than you do; choosing instead to quote magazine and web site articles out of context. In fact, I did exactly the same biamp experiment with my B&W 801 speakers way back in the 80's. Except that I did it correctly, making sure I precisely matched the drive levels, phase, and frequency response of the 2 amplifiers. So you haven't stumbled onto anything new here. (BTW, my results were pretty marginal) You claim, with absolutely no proof, that this "stunning" (your word) "improvement" is because of reduced IM distortion and less modulation of the supply rails. But you completely ignore what is indeed the "elephant in the room" causing, in large part, the audible change you hear. And that is the fact that you are radically altering the original amplitude response of your AR3a speakers. No speculation needed, this is a fact. Look at any book about speaker design, and you will learn that frequency response is by far the greatest determining factor of a speaker's sound. By altering the frequency response of the driving amplifiers to a degree which is unknown to you or anyone else, you are greatly increasing the chances that the overall frequency response is being changed substantially. But that isn't the worst of it. By having to use 2 uncalibrated volume controls, you are relegating the drive level balance, and by extension, the frequency response, to something that is totally arbitrary. Basically, you have created what is essentially a complicated tone control. I run a set of true active speakers myself (Linkwitz Orions), and precise adjustment of the crossover levels is critical to getting them to perform properly. Even a 1/2 dB shift in treble shelving results in a considerable change to the total balance. God only knows how much shelving you've introduced, and in which direction. Then you go even further in this by trying to dismiss the importance of the 2 amps being in phase with each other. I'm not going to go back into this, but suffice it to say you couldn't be more wrong on this point. If you really want to know the degree to which using separate amplifiers in this way changes the audible performance of your speakers, then you must first remove the obvious variables that are well known to impact the sound. If instead you are just interested in tweaking your speakers through arbitrary means, then have at it. Just don't expect anyone to buy into your theories. Finally, I'd suggest you not argue facts with Dick Pierce. He's extremely knowledgeable about this subject, and you'd be wise to try to grasp what he is saying. |
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#23
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Bi-amping the AR-3a cheaply and non-invasively stunning
John Stone wrote:
Finally, I'd suggest you not argue facts with Dick Pierce. He's extremely knowledgeable about this subject, and you'd be wise to try to grasp what he is saying. Actually, I would not support your suggestion. Indeed, arguing on a factual basis can lead to new discoveries. This is not to say that this is the case here, because despite the original poster's obvious enthusiasm, blessed little in the way of factual data has been advanced. There has been a lot of unsubstantiated specualtion and mention of "tests," nit no data. I would welcome and indeed invite the original poster to, in fact, present actual data, because it would then begin to make the discussion more interesting and informative. |
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#24
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Bi-amping the AR-3a cheaply and non-invasively stunning results
BEAR wrote:
IF the tone controls work entirely "out of band" (ie. the treble control ABOVE the LP filter for the woofer, etc...) then there is certainly benefit to be had by this method OVER the original single AR1500 running the AR3 speakers. That's a mighty big IF there. Granted, turning down the treble on the amp driving his woofers is probably having little effect. (It's also probably doing little to relieve the amp, though, unless he's listening to music with unusual high-frequency levels.) But he's also turning down the bass control on the amp driving his midrange, which is very likely to be having an impact on frequency response. In effect, he's turning down his lower midrange. bob |
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#25
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Bi-amping the AR-3a cheaply and non-invasively stunning
I have a pair of AR3As that I am using as sub-woofers. The strap has
been removed and the speakers (in SERIES) are driven by an Apt-1 power amp. There is a Dalquist dividing unit that only feeds the low bass to the amp. My main speakers are DBX Soundfield ones and I have the bass control set at full cut. ---MIKE--- In the White Mountains of New Hampshire (44° 15' N - Elevation 1580') |
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#26
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Bi-amping the AR-3a cheaply and non-invasively stunning results
bob wrote:
Jerry wrote: bob wrote (on 8/4/2006): Sure, but the primary advantage (and maybe the only advantage) to this set-up over a single amp (powerful enough to drive the speaker, of course) derives from the use of an electronic crossover in place of the passive crossovers inside the speaker. And how big an advantage that is depends largely on how bad the passive crossovers are. Well, Bob, Wharfedale doesn't agree with you: http://www.wharfedale.co.uk/faq.php?show_faq=8 Nothing here that disagrees with what I said. They're talking about passive bi-amping as a means of increasing available power. If you need more power, bi-amping is one way to get it, but it isn't necessarily any better than just buying the right amp in the first place. Actually, passive biamping doesn't increase the available power as assuming two identical amplifiers, the available voltage is the same whether one or two amps is being used. S. |
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#27
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Serge wrote (on 8/5/2006):
If I may be allowed a little pedantry, "real" biamping, as described above i.e. where the crossover is done electronically at signal level, is properly described as Active Operation. The term "biamping" is used for "passive biamping" i.e. where the crossover is done at 'speaker level, and is, as Walt has quoted, a waste of money and effort. If this convention were to be followed, it would remove all ambiguity. S. Well, Serge, fortunately I decided to experiment and NOT listen to the experts. On MY system with MY AR-3a's "passive bi-amping" made a huge difference! One thing about passive bi-amping is that it's fairly easy to return to single amp configuration. So, today I went back to single amp for about an hour and the AR-3a's: 1. seem "lifeless" 2. had no "punch" in the bass 3. lacked clarity So, I returned to my "passive bi-amping" and like magic ... everything returned. Serge, I believe I've been fairly honest, when I say I'm NOT really sure why it's better. I have theories, but that's all. I further admit it might be "dumb luck", that is: 1. the drivers in my speakers are actually in phase now (differences in phase between the amps brought the drivers in-line) 2. could be that old, cheap Pioneer amp is doing a better job on the high frequencies than my AR1500 (now I seriously doubt that's the case, but who knows. The Pioneer is at least 15 years newer than the AR1500) Whole purpose in starting this tread was to share with other AR owners my positive experience. Please remember that the early AR's were never designed for "passive bi-amping". Due to a few chance coincidences, I learned it can be done WITHOUT opening the sealed boxes. Let me repeat that ... WITHOUT opening the sealed boxes. Further, the cost to me was essentially .... zero. The Pioneer amp was just collecting dust in my basement. Even though I had good results on my AR's, I would NOT recommend that other AR owners rush out and purchase a 2nd amp. If you don't have a 2nd amp lying around, borrow one from the kids. In closing, I will say, Serge, I really, really like your suggestion on terminology. That is, Active Operation = electronic xover Thanks, Serge! Regards, Jerry |
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#28
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Bi-amping the AR-3a cheaply and non-invasively stunning results
"Serge Auckland" wrote in message
Lastly, I'm experiencing terrific improvements in imaging, transient response and high frequency definition/ clarity and my xovers are intact. Bob, it has to more than just the xovers. The stress on the amps caused by the woofers just has to playing some role. Normally, I would suggest that all instances of biamping with passive crossovers is a waste of time, as it *can't* make a difference with normal modern high-current amplifiers and loudspeakers with a *normal* impedance characteristic. However, here, I think, we have the example that proves the rule. Firstly, the loudspeakers in question have an extreme impedance characteristic that is a severe load for an amplifier. Secondly, the original amplifier being used is not a modern high-current output amplifier, but a vintage unit with limited current capability. Consequently, passive biamping *in this case* can be beneficial, as separating the lf and hf currents will lessen the load on the power amplifiers being used. If this works for the OP fine, but I think he would get considerably better results with a single modern high-current capable amplifier and normal single wiring using thick low-resistance cable. Measurements can verify this, if the OP is sufficiently interested and/or has the equipment to do the measurements. S. Thanks, Serge! My point in starting this thread is that I don't believe I'm alone. That is, there are a number of us "old timers" that have AR-3's, AR-2's and AR-3a's (40 year old speakers) AND vintage amps. I'm just dying for someone with similar hardware to try "passive bi-amping" on AR's and see whether you get similar results. Please remember that the AR's were never designed for "passive bi-amping", but under the right conditions it can be done WITHOUT opening the sealed boxes. Regards, Jerry |
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#29
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Bi-amping the AR-3a cheaply and non-invasively stunning results
"bob" wrote on 8/5/2206:
Bob, it has to be more than just the xovers. The stress on the amps caused by the woofers just has to be playing some role. Why? Because science just has to work the way you want it to? Dream on, my friend. If you've got a lousy amp that isn't capable of driving your speaker, then taking some of the load off is a good idea. But the premise of everything here is that you have a lousy amp to start with. bob Hi, bob! You might be correct about the amp. I have a slightly more modern amp rated at 150 watts per channel rms into 8 ohms. Output rail voltages are +/- 72 volts ... almost double the rail voltages on the AR1500. Have no idea what the rating is for 4 ohms, but I'd guess somewhere in the 200 watt range. That amp powers my TSW610's (a newer vintage AR speaker from the Teledyne era). One of these days, I'll bring it into my den (damn thing weighs a ton) and have it power the AR-3a's. All things considered I really have this backwards as the TSW610's are 8 ohms and way more efficient than the AR-3a's. I read somewhere that the impedance on the AR-3a's drops below 3 ohms on some of the low frequencies. The AR-3a's might stress most amps! In thinking about this, most reviews of the AR-3a's went along the lines of ..... "great deep bass, but somewhat subdued/dull in the high frequencies". Maybe I've blundered into the reason for this. Regards, Jerry |
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#30
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Bi-amping the AR-3a cheaply and non-invasively stunning
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#31
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
Serge, I believe I've been fairly honest, when I say I'm NOT really sure why it's better. I have theories, but that's all. I further admit it might be "dumb luck", that is: 1. the drivers in my speakers are actually in phase now (differences in phase between the amps brought the drivers in-line) 2. could be that old, cheap Pioneer amp is doing a better job on the high frequencies than my AR1500 (now I seriously doubt that's the case, but who knows. The Pioneer is at least 15 years newer than the AR1500) Well, instead of idle speculation, we can look at what you're actually doing, and the actual effect this is having on the sound. Why does your "bi-amp" approach sound better to you? Here are the possibilities: 1. Power: Your old amp couldn't drive the entire speaker, but can drive just the woofer, so you're getting less clipping. 2. Frequency Response (Bass): By using a separate volume control for your woofer, you are in effect creating a two-band equalizer. And you equalized it to a sound you like better. 3. Frequency Response (Midrange): By turning down the bass control on the amp driving the midrange, you are attenuating the lower midrange. Combined with #2, you now have a 3-band equalizer. 4. Overall Volume: It's possible that you are playing your new system subtly louder than the old, which will likely make the new system sound better. (And, no, you cannot level-match by ear.) 5. Imagination: Your impression of the sound may be influenced by your pride at having devised such a clever set-up. That's it, as far as I can see. bob |
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#32
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
Serge wrote (on 8/5/2006): Snip Well, Serge, fortunately I decided to experiment and NOT listen to the experts. On MY system with MY AR-3a's "passive bi-amping" made a huge difference! One thing about passive bi-amping is that it's fairly easy to return to single amp configuration. So, today I went back to single amp for about an hour and the AR-3a's: 1. seem "lifeless" 2. had no "punch" in the bass 3. lacked clarity Hmmm...at this point, I would question why you would have listened to lifeless, muddy, punch-free speakers for 40 years? There had to have been a reason. You may well find, as a consequence, that the *new* livelier sound (i.e. with the modified frequency response you've introduced) may well become fatiguing as time goes on...then again, maybe not. Keith Hughes |
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#33
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
I read somewhere that the impedance on the AR-3a's drops below 3 ohms on some of the low frequencies. The impedance of the AR3a The AR-3a's might stress most amps! Not if you're playing, as you said earlier, at levels of 1 watt or less. In thinking about this, most reviews of the AR-3a's went along the lines of .... "great deep bass, but somewhat subdued/dull in the high frequencies". Maybe I've blundered into the reason for this. No, the reason for this is that Roy Allison and Ed Villchur at AR decided on a balance that resulted in an overall downward trend in the speaker's response toward the high end. That was their choice, for whatever reaons. The midrange efficiency is about 2 db less than the woofer, and the tweeter is another 2-3 dB less efficienct than that. That's what the people of AR designed it to be. Add to that the woofer was designed purposely to be under- damped, with a system Qt at resonance of about 1.2-1.25. One reaons for doing this is that it results in the highest possible efficiency for a sealed-box system of that size and cutoff frequency. Given the standard efficiency, enclosure volume, cutoff frequency relation: n0 = kn Vb F3^3 where n0 = reference efficiency, Vb is enclosure volume F3 is -3dB cutoff frequency and kn is the alignment- dependent efficiency constant, we find that kn is at a maximum when Qtc = 1.1 or so, where kn reaches a maximum value of 2.0 * 10^-6 (cf Small, JAES pp 290, 1972 Dec). Thus, I think this is yet more evidence that, without either knowing it or not wanting to know it, you have probably rather drastically altered the overal frequency response of the system. Given I have seen untold numbers of people perform, in essence, the same experiment you have, and, without a single exception, all such experiments resulted in pretty radical alteration of the system's frequency response, I'd wager good money that's exactly what you've done, and you like the results. Wanna take the bet? |
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#34
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
1. the drivers in my speakers are actually in phase now (differences in phase between the amps brought the drivers in-line) Several points: 1. What on earth would lead you to such a conclusion? Do you, in fact, know that there is "a difference in phase?" 2. If your speculation is true that, in fact, the two amplifiers are "different in phase," the result, given the basic intrinsic nature of these sorts of systems IS a change in frequency response, which contradicts your assertions to the contrary. |
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#35
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Jerry wrote:
Well, Serge, fortunately I decided to experiment and NOT listen to the experts. This is somewhat reminiscent of the most common last four words of a lot of men, "Hey guys, watch this!" :-) Beyond that, what experts might that be? You seemed be able, at the drop of a hat, drop in links to manufacturer's web sites in an attempt to bolster your claims. On MY system with MY AR-3a's "passive bi-amping" made a huge difference! I think there is no dispute about that at all. It's just that you don't know WHY it made a difference, and some here who have actually seen the experiment done, and some here who actually know abnout these things a bit more than you do, have reasonably advanced the suggestion that the huge difference you hear could well be due to the huge difference in the resulting frequency response of the system that would inevitably result from what you have done. And you have not advanced a single piece of evidence to suggest to the contrary. That's all. |
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#36
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Bi-amping the AR-3a cheaply and non-invasively stunning results
"Keith Hughes" wrote in message
... Jerry wrote: Serge wrote (on 8/5/2006): Snip Well, Serge, fortunately I decided to experiment and NOT listen to the experts. On MY system with MY AR-3a's "passive bi-amping" made a huge difference! One thing about passive bi-amping is that it's fairly easy to return to single amp configuration. So, today I went back to single amp for about an hour and the AR-3a's: 1. seem "lifeless" 2. had no "punch" in the bass 3. lacked clarity Hmmm...at this point, I would question why you would have listened to lifeless, muddy, punch-free speakers for 40 years? There had to have been a reason. You may well find, as a consequence, that the *new* livelier sound (i.e. with the modified frequency response you've introduced) may well become fatiguing as time goes on...then again, maybe not. Keith Hughes Keith, that is a very good question, as I have a modern set of JBL's and more modern (well 20 years newer AR's). Both of these sound brighter and clearer than my AR-3's prior to bi-amping. My favorite music is jazz and in particular jazz trios/quartets. Us AR lovers, and there are quite a few us still around, just love the "tight, deep bass" produced by the acoustic suspension design. Today, with the exception of a few sub-woofers (made by companies like Velodyne) is very hard to find acoustic suspension systems. Ported speakers are OK and sound nice, but it's just NOT the same. Hope this helps ... Regards, Jerry |
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#37
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Bi-amping the AR-3a cheaply and non-invasively stunning results
Serge Auckland wrote on 8/6/2006:
Actually, passive biamping doesn't increase the available power as assuming two identical amplifiers, the available voltage is the same whether one or two amps is being used. S. Serge, it's pretty universally accepted that bi-amping of any kind can increase available power. There are some explanations in this article: http://sound.westhost.com/bi-amp.htm Another way to look at this is that power output is NOT simply a matter of voltage available. Amp ratings are at certain thd levels. Upon stressing the rail voltages, we start to see more clipping (distortion) and further amplification only exponentially increases distortion. With two amps "sharing" the audio spectrum AND the load (that is neither amp sees the curent drain of all the speakers), we'll be able to drive each amp harder before distortion sets in. Thus, resulting in more power available to the system of speakers. Hope this helps, Serge. Regards, Jerry |
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#38
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Bi-amping the AR-3a cheaply and non-invasively stunning
"---MIKE---" wrote in message
... I have a pair of AR3As that I am using as sub-woofers. The strap has been removed and the speakers (in SERIES) are driven by an Apt-1 power amp. There is a Dalquist dividing unit that only feeds the low bass to the amp. My main speakers are DBX Soundfield ones and I have the bass control set at full cut. ---MIKE--- In the White Mountains of New Hampshire (44° 15' N - Elevation 1580') Hi, Mike!! You neglected to say how you like the sound of the AR3a woofers. My own expereince is that the "tight, deep bass" of the acoustic suspension AR's is very difficult to match. Now, you mention that you have the strap removed (as do I), but how about the coil and cap inside the sealed box? Did you disable? Frankly, since you are only sending frequencies to the woofers within their designed range, I don't think the coil and cap are doing much. Lastly, you have the woofers in series with each other?? Clearly that gets you closer to 8 ohms. Is the Apt-1 a mono amp? Mike, I'm just curious why the series connection. Regards, Jerry |
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#39
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Bi-amping the AR-3a cheaply and non-invasively stunning results
bob wrote on 8/6/2006
Hi, bob! I like your questions below and find them thought provoking. I will comment on each and we'll see if that helps clarify things. In all fairness, Bob, you must admit that you are "speculating" as well. Frankly, I see NOTHING wrong with idle speculation as it makes me sit back and think. Well, instead of idle speculation, we can look at what you're actually doing, and the actual effect this is having on the sound. Why does your "bi-amp" approach sound better to you? Here are the possibilities: 1. Power: Your old amp couldn't drive the entire speaker, but can drive just the woofer, so you're getting less clipping. Bob, you may be right on here! It's totally possible that the woofer amp is STILLclipping, but since that amp has no access to high frequency drivers, .... we can't hear it! My problem with this answer, however, is that my normal listening level was approx. 1 watt average (I have meters on the AR1500). I "think" is that old amp is struggling under transient loads (like a plucked bass string) and that in turn causes rail instability which leads to distortion in the higher frequencies. Further, I believe nothing has changed with that old amp, except it no longer has access to high frequency drivers. Compounding the problem is that the amp see the impedance of AR-3a's at some low frequencies under 3 ohms! Then the Pioneer amp, of course, is NOT stressed in the least by the power hungry woofers. 2. Frequency Response (Bass): By using a separate volume control for your woofer, you are in effect creating a two-band equalizer. And you equalized it to a sound you like better. Absolutely, Bob!!! No question about it! But .... and it's a BIG but My only real control is to drive the woofer with either MORE or LESS energy relative to the mid-range/tweeter. I have no EQ which would allow shaping of individual frequency bands. All I have is tone controls. Further the tone controls on the Pioneer are inferior (less attenuation) to the tone controls on the AR1500. Now, here is the interesting part. I've never claimed that with "passive bi-amping" I get MORE bass. Instead, what I claim is "better defined" bass! Further, I know from where this "better definition" is coming. It's coming from the mid-range and tweeter!! How is that, Bob, for perplexing? I know this is the case, because when listing to a jazz trio with beautiful, well defined base, if I turn the Pioneer off, that better defined base ... disappears! What I call "definition" must have something to do with the harmonics of the string bass. 3. Frequency Response (Midrange): By turning down the bass control on the amp driving the midrange, you are attenuating the lower midrange. Combined with #2, you now have a 3-band equalizer. Ummmm, not shure I buy this and it's my fault, Bob, for failing to share with you my simple experiments. I shut down the AR1500 when playing a piece of music with a decent distribution of frequencies (jazz band not a trio). So only the mid-range and tweeter are producing sound. I then turned the bass tone control on the Pioneer all the way UP (not flat, but all the way up). Result: no difference in music pitch (I heard no hint of increased low frequency or mid frequencies) It appears that the tone controls really work at the extremes of the audio spectrum. Now, and this is "kind of interesting" I think that I can hear a very slight reduction in clarity when I turn the bass control on the Pioneer all the way up. Now this "lack of clarity" appears to impact only the very high frequencies. I find this very strange and really am NOT sure what's going on other than the "theory" that mixing high and low frequencies offers the opportunity for more IM distortion. 4. Overall Volume: It's possible that you are playing your new system subtly louder than the old, which will likely make the new system sound better. (And, no, you cannot level-match by ear.) Bob, this is clearly possible, but I have the power meters and my sense is I now listen to music at slightly lower power levels. Since I can clearly hear all of the instruments and the bass is better defined, I find that I'm satisfied/gratified at slightly lower volumes. Bob, I want to emphasis that the reduction is slight. While before I averaged between .5 and 1 watt, now I'm averaging between .3 and .7 watt. 5. Imagination: Your impression of the sound may be influenced by your pride at having devised such a clever set-up. That is entirely possible, Bob!!! This is exactly why I'm anxious to hear from other AR owner to see what they experience under my scheme. I hope (and pray this is not the case). No engineer wants to believe they have lost their objectivity, but ... it happens. In my defense, I'll say that I've been listening to these AR-3a's for some 35 years. They never had the brilliance or clarity of my other AR's (TSW610's) and now, they are clearly equal, and in many respects superior. That's it, as far as I can see. bob Again, Bob, I appreciate your probing questions. You make me think! Thanks, Jerry |
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Posted to rec.audio.high-end
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Bi-amping the AR-3a cheaply and non-invasively stunning
John Stone wrote on 8/6/2006
Dick, I was only referring to those points Jerry had already brought up in this thread. If he was bringing up points that actually were debatable it would be different. But he is out of his league and doesn't seem to realize it. Arguing with you (or me for that matter) that his setup is not altering frequency response or that back EMF from the woofer is somehow reaching the mid/tweeters is just silly. He has big gaps in his knowledge of basic electronics. That was my point in telling him to try to learn something from what you wrote. John, I don't think I am of out of anybody's league here. I do freely admit that the EMF argument came from Richard, not from me. I really don't know much about EMF in woofer motors. Richard has been involved with AR's for years and understand much of their original design trade-offs. My field is electronics and I've spent many, many frustrating hours over bread boards that aren't perform as they theoretically should. In short, there is a huge step between theory and the "real world" and I have all the scars to prove it. I'm retired now, and have little equipment, but I still understand the theory. To suggest as you folks seem to gravitate towards that all I've done is change the frequency response of the SYSTEM shows I'm NOT "out of my league". Look, frequency response is just one little measurement of a system. It deals with the QUANTITY out vs. a steady, constant input signal sweep over the entire frequency band. It doesn't begin to deal with the QUALITY of that output nor does it deal with dynamics like transient response which are huge issues in sound reproduction. Further, my amps have TONE CONTROLS. I have (on these amps) no EQ's so I simply have no way to shape or emphasize any discrete frequency band. In passive bi-amping the xovers are in place and continue balancing frequencies sent to the various drivers. All I can do (with the amps' volume control) is either UNDER or OVER drive the woofer with respect to the mid-range/tweeter. But, that's trivial!! I could do that before with tone controls and "loudness switches". You undoubtedly know that over or under driving the woofer causes "funky things" to happen with human voices and I just love Ella Fitzgerald. After all these years, I can assure you I can adjust to get her voice correct in seconds. Lastly, someone on here was trying to tell me how power amps wattage rating is based upon the amp's rail voltages. This particular individual is clearly NOT in my league. Rail voltages MUST be way above any amp's power rating to provide "head room" to minimize clipping and the resulting distortion. That is, music is not a steady, constant input signal. It's just full of transients and amplifier engineers understand this. In any event, that individual will shortly fry his amp, if he truly believes his convictions. Regards, Jerry |
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