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#201
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Yahama "natural sound" amp specs?
"Scott Dorsey" wrote in message ... Mike Rieves wrote: But you don't use them for near field monitors, do you? :-) I could see using Magnepans in a great room for far field or main monitors, but not without a good pair of nearfields for the fine work. Maggies do have awesome midrange clarity. No, I never really got the whole near-field thing. When near field monitoring started coming in, it came in with a huge amount of hype about eliminating room problems and how you wouldn't have to treat the room any more. Needless to say this turned out to be false. But in the eighties I saw folks just going berserk over the idea and I never felt like I ever liked working thhat way. I'll occasionally track on nearfields and I use them in the truck all the time because there just isn't room for a decent monitoring system. But for the most part I don't really like mixing on nearfields at all if there is a good alternative. Then again, I learned to mix on Altec 604s. Thank God that those days are over. --scott My main monitors' location would qualify them as mid field and I've treated the room appropriately, and I use them for the actual mixing and imaging, but I do depend on my near fields for details and relative balance. Doing all the mixing on near fields is as difficult as doing it all on mid or far fields, but those with home studios often have no choice, the area is often small and cramped and SPL levels can often be a problem since others are living in the house or since it may be in an apartment, preventing the use of larger monitor speakers located further away from the mixing position. In the final analysis, if you're getting good mixes, it doesn't matter what you're getting them with. :-) |
#202
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
"Pooh Bear" wrote in message ... David Nebenzahl wrote: Pooh Bear spake thus: CWCunningham wrote: And while you're here, what's wrong with measuring into a resistive load? And if there's a qualitative reason that it's "not good" to measure into a resistive load, why do you do it that way? Because it's the only possible standard. Once you get into xR +/- yj you can have multiple combinations of x and y and + or -. Not to mention the test frequency too. So I'm curious what you think of Arny Krueger's reactive dummy load: http://www.pcabx.com/product/amplifiers/index.htm. Nobody has commented on this yet. It's just *an example* of what's possible. It is one example of the millions of possible example and meaningless, for that reason. Here's a real-world example of just what I was proposing: a load that combined resistance and reactance to mimic an (average) real-world load (i.e., a speaker). With an admittedly arbitrarily-chosen topology, if that's the right word; hey, you have to choose one. All reactive loads will be arbitrary. Resistive ones aren't. Hence that's why they're used. Common playing field. It clearly says "simulated" so it isn't even a real example. It certainly isn't typical, because there is no typical speaker load simulator, if there were, everyone would be using it. |
#203
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
"CWCunningham" charlesw-at-blackfoot.net wrote in message ... Mike states, "All of them rate their amps when driving purely resistive loads, and those are the ratings they publish, they are the ratings listed in the owners' manuals and in the advertisements for the product". This is actually false. Consider http://www.soundstage.com/gettingtec...ical200503.htm NAD says they rate their amp using a "difficult 4-ohm load", they don't say it isn't a resistive load. So how is what I said false? Rating output power into 4, 2 or even 1, ohm isn't unheard of, but they do use resistive loads. NAD amps are rated with all channels driven and they do have very stiff power supplies so the amps can drive difficult loads. One the differences between really good studio amps and run of the mill hifi amps is the stiffness of the power supply. A stiff supply will not drop on voltage when driven hard, a soft one will, and many hifi amp makers use soft supplies to cut costs while allowing them to keep power ratings high. Also note that while requiring manufacturers to rate their amps a certain way to conform with the FTC rule, it doesn't preclude them from using other methods as well. You sometimes see amps rated at "XXX" watts music power, with the actual FTC rating being further down the page and the FTC power rating may be considerably lower than the "music power rating. | It's called the 'amplifier rule' btw and was recently updated to take account of | recent new product categories such as powered/active speakers. | http://www.ftc.gov/opa/2000/12/amprule.htm | Note in the provided link how the engineers at NAD describe the ammendments as a loosening of the rules such that an amp will spec more powerful than it could under the original rules. NAD does design their amps to drive loads with difficult impedances, including reactance, but they still rate them using resistive loads, just as I said. I agree with NAD, that the recent changes in the rule have made it more difficult for the end user to assess an amp by its published specs, and that is why I keep saying auditio the amp with speakers like the ones you'll be using! :-) |
#204
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Arny Krueger wrote:
"Les Cargill" wrote in message Arny Krueger wrote: "Pooh Bear" wrote in message snip One simple reason for this is that reactance doesn't dissipate energy so you couldn't use *watts* for the spec. This is in fact an interesting point. It would in fact be somewhat smarter to spec amplifers in terms of *voltage* output but it would be a task and a half to change decades of established practice. Speccing amps in volt-amps would be even more to the point. ??? Aren't volt-amps and watts purty near the same thing? No, volt-amps and watts can be vastly different numbers. An ideal reactive load dissipates no power, so the volt-amps delivered to a reactive load could be lots while the watts could very small. Well, of course. Even for sub-ideal inductors, the differences can be significant. 8 ohm speakers often measure about 5 ohms resistance - that's how my Dad first taught me about inductance. So how far apart are they for typical audio amp - loudspeaker interfaces, then? Assume you have a speaker that's 8 ohms, but 5 ohms resistance. Are you telling me that a power amp putting out SQRT(12.5) volts of 1000 Hz sine wave into that speaker is only actually dissipating 62.5 watts instead of 100? -- Les Cargill |
#205
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Arny Krueger wrote:
"Les Cargill" wrote in message Arny Krueger wrote: "Pooh Bear" wrote in message snip One simple reason for this is that reactance doesn't dissipate energy so you couldn't use *watts* for the spec. This is in fact an interesting point. It would in fact be somewhat smarter to spec amplifers in terms of *voltage* output but it would be a task and a half to change decades of established practice. Speccing amps in volt-amps would be even more to the point. ??? Aren't volt-amps and watts purty near the same thing? No, volt-amps and watts can be vastly different numbers. An ideal reactive load dissipates no power, so the volt-amps delivered to a reactive load could be lots while the watts could very small. Ah, scratch my other post. You said re*act*anc,e not re*luct*ance. Ne'er mind... Amp-speaker interfaces are generally not very reactive, yes? -- Les Cargill |
#206
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Mike Rieves wrote: Also remember that there are different rating methods currently in use, making it even more confusing. I've seen amps rated as: "RMS continuous power ", "RMS music power", "RMS peak power", "peak power", and others, none of which have much in common. With so many rating methods now in use, adding more will only increase the confusion, not clarify anything. FTC requires power to be rated as continuous average power ( the same as what's typically called 'rms power' ). Graham |
#207
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Pooh Bear wrote:
Mike Rieves wrote: Also remember that there are different rating methods currently in use, making it even more confusing. I've seen amps rated as: "RMS continuous power ", "RMS music power", "RMS peak power", "peak power", and others, none of which have much in common. With so many rating methods now in use, adding more will only increase the confusion, not clarify anything. FTC requires power to be rated as continuous average power ( the same as what's typically called 'rms power' ). Note that the FTC regulations only apply to advertisements of home stereo gear in the US. The car stereo people and boom box people and (the very worst) computer people can still advertise ONE MILLION WATTS PEAK MUSIC POWER OUTPUT. Pro audio gear usually follows FTC guidelines but doesn't always, and you will occasionally see some goofy numbers here and there. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#208
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
"Pooh Bear" wrote in message ... Mike Rieves wrote: Also remember that there are different rating methods currently in use, making it even more confusing. I've seen amps rated as: "RMS continuous power ", "RMS music power", "RMS peak power", "peak power", and others, none of which have much in common. With so many rating methods now in use, adding more will only increase the confusion, not clarify anything. FTC requires power to be rated as continuous average power ( the same as what's typically called 'rms power' ). Graham You're right, but as long as the FTC rated power is displayed somewhere in the specs, they're free to use other ratings as well. You see it all the time on car amps, boomboxes and home theater systems. |
#209
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Mike Rieves wrote:
Since this discussion is primarily about studio monotors and studio control rooms (especially home studio control rooms) are often quite small, there can enough room effect on the cone dynamics to make a measureable difference, enough to cause an audible difference in the speaker's sound. Citation please? Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
#210
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Scott Dorsey wrote: Pooh Bear wrote: Mike Rieves wrote: Also remember that there are different rating methods currently in use, making it even more confusing. I've seen amps rated as: "RMS continuous power ", "RMS music power", "RMS peak power", "peak power", and others, none of which have much in common. With so many rating methods now in use, adding more will only increase the confusion, not clarify anything. FTC requires power to be rated as continuous average power ( the same as what's typically called 'rms power' ). Note that the FTC regulations only apply to advertisements of home stereo gear in the US. The car stereo people and boom box people and (the very worst) computer people can still advertise ONE MILLION WATTS PEAK MUSIC POWER OUTPUT. For the life of me I can't understand why they still allow this. Pro audio gear usually follows FTC guidelines but doesn't always, and you will occasionally see some goofy numbers here and there. I can't say I have myself. Do you have any examples ? Graham |
#211
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
"Mike Rieves" wrote in message
David, old boy, what did you not understand about: "That's easy, in simple terms, the air in the room acts as a spring (the smaller the room, the more powerful the spring) which acts on the speaker cone's motion, which in turn has an effect on the voice coil movement, which has an effect on the electromotive mechanism. This is reflected back to the amp output as an impedance change. Standing waves in the room may also have an affect as well. This isn't something made up for this news group, that fact that the room affects a speaker's overall reactance has been known for many years. Anyone who knows anything about speakers knows that the enclosure the speaker is installed in has a major effect on a speaker's characteristics, including impedance, but some may not realize that the room is actually another enclosure on the other side of the speaker, and it has an effect as well. Typically, the back of the speaker cone is loading into the enclosure and the front of the cone is loading into the room." How is that nebulous? It lacks quantification. If you were technically competent Mike, you'd have already tried to measure it, and you'd know that it is a nit. |
#212
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
"Les Cargill" wrote in message
Arny Krueger wrote: "Les Cargill" wrote in message Arny Krueger wrote: "Pooh Bear" wrote in message snip One simple reason for this is that reactance doesn't dissipate energy so you couldn't use *watts* for the spec. This is in fact an interesting point. It would in fact be somewhat smarter to spec amplifers in terms of *voltage* output but it would be a task and a half to change decades of established practice. Speccing amps in volt-amps would be even more to the point. ??? Aren't volt-amps and watts purty near the same thing? No, volt-amps and watts can be vastly different numbers. An ideal reactive load dissipates no power, so the volt-amps delivered to a reactive load could be lots while the watts could very small. Well, of course. Even for sub-ideal inductors, the differences can be significant. 8 ohm speakers often measure about 5 ohms resistance - that's how my Dad first taught me about inductance. So how far apart are they for typical audio amp - loudspeaker interfaces, then? Assume you have a speaker that's 8 ohms, but 5 ohms resistance. That is unrealistically simple for a speaker. The magnitude of the impedance of a speaker can easily range from 0.75 of rated impedance to 10 times rated impedance and back again, maybe several times over the regular audio band. It is not unusual for the impedance of a speaker to have a phase angle of 45-60 degrees at some frequencies. I studied this out once, and built a circuit that behaved like a reasonable worst case loudspeaker. Here are the impdeance magnitude and phase angle curves: http://www.pcavtech.com/techtalk/wir...mulator-mag-hi http://www.pcavtech.com/techtalk/wir...imulator-phase Are you telling me that a power amp putting out SQRT(12.5) volts of 1000 Hz sine wave into that speaker is only actually dissipating 62.5 watts instead of 100? Depends on what the impedance of the speaker is at 1 KHz. I found that a reasoanble worst-case 4 ohm 2-way speaker might have an impedance of about 12 ohms at 1 KHz. Letsee if my 40 year-old recollections of EE classes are any good: The phase angle of the impedance of my reasonble-worst-case speaker at that point was about 37 degrees. The real (resistive) component of the impedance at that frequency would be about 9.5 ohms. The imaginary (reactive) component of the impedance at that frequency would be about 7.2 ohms. If you applied 12 volts across this speaker, the speaker would draw about an amp over-all, but there would be a out-of-phase current drain that would be more like 1.7 amps. The power amp would therefore be required to provide more like 20 volt-amps. |
#213
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Bob Cain wrote:
Mike Rieves wrote: Since this discussion is primarily about studio monotors and studio control rooms (especially home studio control rooms) are often quite small, there can enough room effect on the cone dynamics to make a measureable difference, enough to cause an audible difference in the speaker's sound. Citation please? I don't think it should be significant, but it just so happens that I have speakers set up in an empty room and an impedance bridge. Let me do a plot on them, and see how it changes when the rugs and furniture are in and the room is less live. I doubt it'll be as much as 1%, but it'll be interesting to see and minimal effort to measure. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#214
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Pooh Bear wrote:
Scott Dorsey wrote: The car stereo people and boom box people and (the very worst) computer people can still advertise ONE MILLION WATTS PEAK MUSIC POWER OUTPUT. For the life of me I can't understand why they still allow this. I find it less offensive than the magnets that are advertised as improving your gas mileage or the copper bracelets advertised as helping arthritis. Pro audio gear usually follows FTC guidelines but doesn't always, and you will occasionally see some goofy numbers here and there. I can't say I have myself. Do you have any examples ? Well, on the GOOD side you'll see folks like QSC which list power ratings on the data sheet with both FTC and EIA methods. On the BAD side you'll see American DJ. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#215
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
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#216
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
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#217
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Scott Dorsey wrote:
I don't think it should be significant, but it just so happens that I have speakers set up in an empty room and an impedance bridge. Let me do a plot on them, and see how it changes when the rugs and furniture are in and the room is less live. I doubt it'll be as much as 1%, but it'll be interesting to see and minimal effort to measure. Very cool, Scott! Placement in the room would also be an interesting variable. Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
#218
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
On Fri, 02 Jun 2006 14:04:41 -0700, Bob Cain
wrote: Scott Dorsey wrote: I don't think it should be significant, but it just so happens that I have speakers set up in an empty room and an impedance bridge. Let me do a plot on them, and see how it changes when the rugs and furniture are in and the room is less live. I doubt it'll be as much as 1%, but it'll be interesting to see and minimal effort to measure. Very cool, Scott! Placement in the room would also be an interesting variable. Bob There might be a tiny change around the LF resonance points, but I wouldn't expect anything elsewhere. d -- Pearce Consulting http://www.pearce.uk.com |
#219
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Scott Dorsey wrote:
I don't think it should be significant, but it just so happens that I have speakers set up in an empty room and an impedance bridge. Let me do a plot on them, and see how it changes when the rugs and furniture are in and the room is less live. I doubt it'll be as much as 1%, but it'll be interesting to see and minimal effort to measure. See? There is an up side to moving. Peace, Paul |
#221
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Mike Rieves wrote: "David Nebenzahl" wrote in message .com... First, let me say that I come to this argument late, as a long- overdue vacation to Wales and Ireland stood betwixt myself and the regrettably common rec.audio techno-babble.. Mr Rieves makes very specific technical assertions regarding the electrical behavior of loudspeakers in rooms. Any assertions that the impedance/reactance changes appreciably due to change in the "sonic environment" (whatever the ****** that is) are just audiophool pixie-dust fantasies. Like maybe small changes in barometric pressure? Relative humidity? Come on; this ought to be good. Explain away. Get specific. That's easy, in simple terms, Good, then we shall evaluate as you suggest.. the air in the room acts as a spring (the smaller the room, the more powerful the spring) which acts on the speaker cone's motion, which in turn has an effect on the voice coil movement, which has an effect on the electromotive mechanism. This is reflected back to the amp output as an impedance change. First, Mr. Rieve4s makes several very specific technical assertions. Let's deal with each of those in turn. "the air in the room acts as a spring (the smaller the room, the more powerful the spring)" Well, in a technically inaccurate, viceral sort of way, maybe. Springs, however, aren't "powerful." Springs, mechanical reactances, don't have power any more than masses or capacitances or inductances do. Springs have, not surprisingly stiffness. That stiffness can be shown, as any reasonable text on acoustics will show (check Beranek, Kinsler and Frey, Blackenstock, etc.), to be a reciprocal function of the volume. And that is the basis of our analysis of Mr. Rieves' assertions. He further asserts: "Anyone who knows anything about speakers knows that the enclosure the speaker is installed in has a major effect on a speaker's characteristics, including impedance, but some may not realize that the room is actually another enclosure on the other side of the speaker, and it has an effect as well. Typically, the back of the speaker cone is loading into the enclosure and the front of the cone is loading into the room." Mr. Rieves has conveniently provided us with the means of evaluating his own assertion. Let's do just exactly that. As we have already stated, the stiffness of an enclosure is proprotional to the reciprocal of its volume. Using this well- established principle, we can evaluate directly the effect of the room on. To do so, let's make some assumptions, chosen, in fact, to support Mr. Rieves' assertions as much as possible. Those assertions include: 1. A sealed box acoustic-suspension loudspeaker whose internal volume is 1.5 cubic feet. We chose this configuration to directly support Mr. Rieves' assertion, and it represents a typical value for high-performance systems of this type. In such a system, the enclosure stiffness dominates the suspension's mechanical stiffness and is the determining factor in the system stiffness. 2. We will assume a listening room whose dimensions are 8 feet high, 12 feet wide and 15 feet long, whose internal volume is approximately 1500 cubic feet. We will assume this room has absolutely rock-solid, totally reflective walls, there is no absorbtion in the room at all, and that the room is tightly sealed, with no doors, windows, vents or other means by which air can enter or escape. The same can be said for any uccupants as well. 3. We will compare the performance in the room to the performance in absolute free air. So, since the acoustical stiffness is proportional to the reciprocal of the volume, we have a direct means of comapring the effect of each, according to Mr. Rieves. The total stiffness felt by the cone is, in fact, simply the linear sum of all stiffnesses. And since the room has a volume that 1/1000 that of the enclosure, we can reasonably deduce that it's stiffness is 1/1000 that of the enclosure. Thus the total system stiffness of the entire system, including the room, has been changed by 1+1/1000 or 1.001 times that of the speaker in a totally free environment. Let's examine some the consequences of that 1. Change to system resonance This is, in fact, the ONLY substantive change that can happen, for a couple of reasons. First, Despite Mr. Rieves' assertions to the contrary, stiffness will only have an effect at and below fundamental resonance, as the system is mass controlled above resonance, This is why, for example, changing the enclosure size for a given driver has NO impact on reference efficiency. Second, changing the total system stiffness WILL affect both the resonant frequency AND the system Q at resonance (due to the increased reactance provided by the additional stuffness). The resonance of the system goes as: F = 1/(2 pi) * 1/sqrt(M/K) where M is the effective moving mass, and K is the total stiffness. We'll assume that the stiffness is determined solely by the acoustic stiffness of the enclosure and the room (as any additional stiffnessses, such as the suspension, will simply diminish the effects of the room stiffness). Given that, we can directly evaluate how much the resonance changes: F' = 1/(2 pi) * 1/sqrt(M/1.001) Since we are looking simply at the effect of changing one parameter, K, M can be considered a constant and f' will simply be the ratio of the change in resonant frequency. The result of evaluating this relation is that the room will change the resonant frequency by 0.05%. And since damping goesd as the resonant frequency, the system Q will change by a similar 0.05%. Thse figures are substantially smaller than can be reliably measured using the best current methods. For comparison, let's put that same speaker in a room that's half the total volume, say 8 feet tall by 8 feet wide by 11 feet long. Now the resonance will change by a whopping 0.1%. 2. Confounding factors The enclosure and room acoustical stiffness are NOT the conly contributing factors. We purposely ignored the mechanical stiffness to maximize the potential effects of the room. We can't ignore the mechanical stiffness simply because it is SO much larger than that provided by the room. In a typical acoustic suspension system, the mechanical stiffness of the suspension is usually no more than 1/4-1/3 that of the enclosure (this larger ratio is what defines "acoustic suspension"). Thus, that stiffness is on the order of 250 times that of the room. More importantly is the fact that the mechanical stiffness of the suspension is one of the hardest mechanical parameters to control during manufacturing, and variations in the parameter of 20% are not uncommon. Indeed, 20% is considered quite good. Since the suspension stiffness is on the order of 1/4 the total stiffness, changes in that stiffness can be considered to contrinute 1/4 the total cariation in system stiffness. Thus, variations of +-20% in mechanical stiffness result in changes of +-5% in total system stiffness. This means that the simple manufacturing tolerances in the suspension have an effect that's 100 times GREATER than the effect of the room on total system stiffness. Using Mr. Rieves own technical basis for his assertions, it's safe to say that his assertions are shown to be, in essence, bunkum. Standing waves in the room may also have an affect as well. This can alos be evaluated. Any of the above cited texts will show that the total impedance of a loudspeaker is the result, in order of the magnitude of the contribution, to be the electrical portion, the mechanical proportion and the acoustical proportion. Further, it can be shown that the acoustical contribution is, by far, the smallest of all three, and is essentially a function of, at its greatest, the reference efficiency of the system. Seldom does the efficiency of a direct radiator loudspeaker exceed 1%, so one can reasonably expect the effects of standing waves to never influence the impedance in excess of the total contribution of its change in radiation impedance to total system impedance. This is simply born out by the many thousands of impednace curves I have measured of speakers in and out of rooms that show, effectively NO such changes Mr. Rieves asserts must exist that cannot be fully explained by any number of confounding factors, only 1 of which is mentioned above. This isn't something made up for this news group, Well, it would appear that, in fact, it is, since the effect is not documented as Mr. Rieves claims in any of the professional literature. that fact that the room affects a speaker's overall reactance has been known for many years. Known by whom? Would Mr. Rieves be so kind as to cite the specifric references he seems to be alluding to? Now, one of the problems associated with actually proving or disproving Mr. Rieves assertions by measurements is the simple fact that the measurement techniques alone can lead to varations in the data that well exceed the kinds of effects his assertions would suggest exist. For example, simply measuring the same loudspeaker under identical conditions two times n a row will almost certainly lead to detectable differences due to such effects as small changes in voice coil temperature, flexations and changes in suspension due to mechanical hysteresis and relaxation effects, and so on. Attempting to allow such parameters to stabilize over time means that we now must deal with inevitable changes in environment (temperature, prissure, humidity) which can have greater effects thah that of the room. What it seems we have here, yet again, is the application of common intuition aided by a lack of technical expertise in a topic to draw a conclusion that, while, within a very bnarrow context, may seem intuitivgely correcdt, is simply at odds with physical fact. Not an uncommon occurance in audio, to be sure. |
#222
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
wrote in message
oups.com... What it seems we have here, yet again, is the application of common intuition aided by a lack of technical expertise in a topic to draw a conclusion that, while, within a very bnarrow context, may seem intuitivgely correcdt, is simply at odds with physical fact. Not an uncommon occurance in audio, to be sure. But it's not at odds with physical fact. The effects are there. They're simply too tiny to make any real-world audible difference. Peace, Paul |
#223
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Paul Stamler spake thus:
wrote in message oups.com... What it seems we have here, yet again, is the application of common intuition aided by a lack of technical expertise in a topic to draw a conclusion that, while, within a very bnarrow context, may seem intuitivgely correcdt, is simply at odds with physical fact. Not an uncommon occurance in audio, to be sure. But it's not at odds with physical fact. The effects are there. They're simply too tiny to make any real-world audible difference. Which is what I was saying all along in this thread: effects, yes, but inconsequential. Apparently, though, some audio-fools have to be beaten over the head repeatedly by a 50 lb. doctoral thesis before it sinks in. -- Any system of knowledge that is capable of listing films in order of use of the word "****" is incapable of writing a good summary and analysis of the Philippine-American War. And vice-versa. This is an inviolable rule. - Matthew White, referring to Wikipedia on his WikiWatch site (http://users.erols.com/mwhite28/wikiwoo.htm) |
#224
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
wrote in message oups.com... Mike Rieves wrote: "David Nebenzahl" wrote in message .com... First, let me say that I come to this argument late, as a long- overdue vacation to Wales and Ireland stood betwixt myself and the regrettably common rec.audio techno-babble.. Mr Rieves makes very specific technical assertions regarding the electrical behavior of loudspeakers in rooms. Any assertions that the impedance/reactance changes appreciably due to change in the "sonic environment" (whatever the ****** that is) are just audiophool pixie-dust fantasies. Like maybe small changes in barometric pressure? Relative humidity? Come on; this ought to be good. Explain away. Get specific. That's easy, in simple terms, Good, then we shall evaluate as you suggest.. the air in the room acts as a spring (the smaller the room, the more powerful the spring) which acts on the speaker cone's motion, which in turn has an effect on the voice coil movement, which has an effect on the electromotive mechanism. This is reflected back to the amp output as an impedance change. First, Mr. Rieve4s makes several very specific technical assertions. Let's deal with each of those in turn. "the air in the room acts as a spring (the smaller the room, the more powerful the spring)" Well, in a technically inaccurate, viceral sort of way, maybe. Springs, however, aren't "powerful." Springs, mechanical reactances, don't have power any more than masses or capacitances or inductances do. Springs have, not surprisingly stiffness. That stiffness can be shown, as any reasonable text on acoustics will show (check Beranek, Kinsler and Frey, Blackenstock, etc.), to be a reciprocal function of the volume. And that is the basis of our analysis of Mr. Rieves' assertions. He further asserts: "Anyone who knows anything about speakers knows that the enclosure the speaker is installed in has a major effect on a speaker's characteristics, including impedance, but some may not realize that the room is actually another enclosure on the other side of the speaker, and it has an effect as well. Typically, the back of the speaker cone is loading into the enclosure and the front of the cone is loading into the room." Mr. Rieves has conveniently provided us with the means of evaluating his own assertion. Let's do just exactly that. As we have already stated, the stiffness of an enclosure is proprotional to the reciprocal of its volume. Using this well- established principle, we can evaluate directly the effect of the room on. To do so, let's make some assumptions, chosen, in fact, to support Mr. Rieves' assertions as much as possible. Those assertions include: 1. A sealed box acoustic-suspension loudspeaker whose internal volume is 1.5 cubic feet. We chose this configuration to directly support Mr. Rieves' assertion, and it represents a typical value for high-performance systems of this type. In such a system, the enclosure stiffness dominates the suspension's mechanical stiffness and is the determining factor in the system stiffness. 2. We will assume a listening room whose dimensions are 8 feet high, 12 feet wide and 15 feet long, whose internal volume is approximately 1500 cubic feet. We will assume this room has absolutely rock-solid, totally reflective walls, there is no absorbtion in the room at all, and that the room is tightly sealed, with no doors, windows, vents or other means by which air can enter or escape. The same can be said for any uccupants as well. 3. We will compare the performance in the room to the performance in absolute free air. So, since the acoustical stiffness is proportional to the reciprocal of the volume, we have a direct means of comapring the effect of each, according to Mr. Rieves. The total stiffness felt by the cone is, in fact, simply the linear sum of all stiffnesses. And since the room has a volume that 1/1000 that of the enclosure, we can reasonably deduce that it's stiffness is 1/1000 that of the enclosure. Thus the total system stiffness of the entire system, including the room, has been changed by 1+1/1000 or 1.001 times that of the speaker in a totally free environment. Let's examine some the consequences of that 1. Change to system resonance This is, in fact, the ONLY substantive change that can happen, for a couple of reasons. First, Despite Mr. Rieves' assertions to the contrary, stiffness will only have an effect at and below fundamental resonance, as the system is mass controlled above resonance, This is why, for example, changing the enclosure size for a given driver has NO impact on reference efficiency. Second, changing the total system stiffness WILL affect both the resonant frequency AND the system Q at resonance (due to the increased reactance provided by the additional stuffness). The resonance of the system goes as: F = 1/(2 pi) * 1/sqrt(M/K) where M is the effective moving mass, and K is the total stiffness. We'll assume that the stiffness is determined solely by the acoustic stiffness of the enclosure and the room (as any additional stiffnessses, such as the suspension, will simply diminish the effects of the room stiffness). Given that, we can directly evaluate how much the resonance changes: F' = 1/(2 pi) * 1/sqrt(M/1.001) Since we are looking simply at the effect of changing one parameter, K, M can be considered a constant and f' will simply be the ratio of the change in resonant frequency. The result of evaluating this relation is that the room will change the resonant frequency by 0.05%. And since damping goesd as the resonant frequency, the system Q will change by a similar 0.05%. Thse figures are substantially smaller than can be reliably measured using the best current methods. For comparison, let's put that same speaker in a room that's half the total volume, say 8 feet tall by 8 feet wide by 11 feet long. Now the resonance will change by a whopping 0.1%. 2. Confounding factors The enclosure and room acoustical stiffness are NOT the conly contributing factors. We purposely ignored the mechanical stiffness to maximize the potential effects of the room. We can't ignore the mechanical stiffness simply because it is SO much larger than that provided by the room. In a typical acoustic suspension system, the mechanical stiffness of the suspension is usually no more than 1/4-1/3 that of the enclosure (this larger ratio is what defines "acoustic suspension"). Thus, that stiffness is on the order of 250 times that of the room. More importantly is the fact that the mechanical stiffness of the suspension is one of the hardest mechanical parameters to control during manufacturing, and variations in the parameter of 20% are not uncommon. Indeed, 20% is considered quite good. Since the suspension stiffness is on the order of 1/4 the total stiffness, changes in that stiffness can be considered to contrinute 1/4 the total cariation in system stiffness. Thus, variations of +-20% in mechanical stiffness result in changes of +-5% in total system stiffness. This means that the simple manufacturing tolerances in the suspension have an effect that's 100 times GREATER than the effect of the room on total system stiffness. Using Mr. Rieves own technical basis for his assertions, it's safe to say that his assertions are shown to be, in essence, bunkum. Standing waves in the room may also have an affect as well. This can alos be evaluated. Any of the above cited texts will show that the total impedance of a loudspeaker is the result, in order of the magnitude of the contribution, to be the electrical portion, the mechanical proportion and the acoustical proportion. Further, it can be shown that the acoustical contribution is, by far, the smallest of all three, and is essentially a function of, at its greatest, the reference efficiency of the system. Seldom does the efficiency of a direct radiator loudspeaker exceed 1%, so one can reasonably expect the effects of standing waves to never influence the impedance in excess of the total contribution of its change in radiation impedance to total system impedance. This is simply born out by the many thousands of impednace curves I have measured of speakers in and out of rooms that show, effectively NO such changes Mr. Rieves asserts must exist that cannot be fully explained by any number of confounding factors, only 1 of which is mentioned above. This isn't something made up for this news group, Well, it would appear that, in fact, it is, since the effect is not documented as Mr. Rieves claims in any of the professional literature. that fact that the room affects a speaker's overall reactance has been known for many years. Known by whom? Would Mr. Rieves be so kind as to cite the specifric references he seems to be alluding to? Now, one of the problems associated with actually proving or disproving Mr. Rieves assertions by measurements is the simple fact that the measurement techniques alone can lead to varations in the data that well exceed the kinds of effects his assertions would suggest exist. For example, simply measuring the same loudspeaker under identical conditions two times n a row will almost certainly lead to detectable differences due to such effects as small changes in voice coil temperature, flexations and changes in suspension due to mechanical hysteresis and relaxation effects, and so on. Attempting to allow such parameters to stabilize over time means that we now must deal with inevitable changes in environment (temperature, prissure, humidity) which can have greater effects thah that of the room. What it seems we have here, yet again, is the application of common intuition aided by a lack of technical expertise in a topic to draw a conclusion that, while, within a very bnarrow context, may seem intuitivgely correcdt, is simply at odds with physical fact. Not an uncommon occurance in audio, to be sure. Since this was one small part of a discussion of much larger scope, having to do with why manufacturers rate their amplifiers instead of some mythical "typical speaker" reactive dummy load, it's validity has little to do with the overall argument. I will concede that the room's effect is very small compared to other factors, and it may indeed be inconsequential from a practical standpoint, but that does not alter one whit the fact that there is no way to calculate a "typical speaker" reactive load for rating amps. The current method may be a nominal method, but does give some common factors to compare when evaluating amplifiers. As I said here more than once, when buying a new amplifier, you should evaluate the amps with the same speakers you're going to be using. Or don't, whatever strikes your fancy. I got into this discussion because it was cross-posted to alt.music.home-studio, and my comments were in response to a a post asking "Why don't manufacturers use a reactive dummy load typical of a real speaker?" My point was and is that there is no "typical" speaker, and I stand by that. |
#225
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Yahama "natural sound" amp specs?
Mike Rieves wrote: Since this was one small part of a discussion of much larger scope, having to do with why manufacturers rate their amplifiers instead of some mythical "typical speaker" reactive dummy load, it's validity has little to do with the overall argument. Well, no. Whether or not the particular set of assertions you made is applicable to another topic does absolve them of their inherent technical incorrectness. You further stated, clearly, that: "that the room affects a speaker's overall reactance has been known for many years." Again, I ask, "known by whom?" I will concede that the room's effect is very small compared to other factors, and it may indeed be inconsequential from a practical standpoint, but that does not alter one whit the fact that there is no way to calculate a "typical speaker" reactive load for rating amps. Actually, there most assuredly is, and your attempts to suggest otherwise by cobbling up assertion that the room is an important factor by appealing to some unknown and unheard-of authority simply weakens you position further. As I mentioned, I have personally performed many thousands of impedance (and other) measurements on loudspeakers over the last 30+ years. From that massive amount of data, supported by many ore measurements that are available, it most assuredly IS possible to come up with no more than maybe a half-dozen impedance models which cover the vast majority of loads encountered by typical amplifiers. First of all, it's possible, given the relative size of the market segments, to eliminate a number of "pathological" speaker loads. For example, pure electrostatics and hybrids can effectively eliminated from evaluation simply because their penetration into the market is far to small to have any consequence, and they can be dealt with as special cases. The same can be said of most planar speakers and conjugate- compensated speakers, which behave like resistors in any case. By pruning these rare and patholigical cases, we can reduce the problem set to essentially a two-dimensial matrix. One dimension is two-way vs three-way systems, the other dimension is simply moderate nominal impedance (6-8 ohms) vs low impedance (3-5 ohms). All the other variations, such as sealed box vs reflex , crossover frequencies and order, fundamental resonant frequancy and such, while they may lead to a different LOOKING impedance curve, do not lead to any models which result in measurably different performance. Once you have covered these two crucial dimensions and the gross variations in each of those, the departure you have made from simple resitive loading is FAR greater than ANY individual variations due to system tuning, configuration and topology. The current method may be a nominal method, but does give some common factors to compare when evaluating amplifiers. None of which, it can be argued have any relevance to actual in-situ behavior. What you are, in essence, arguing is that since you can't think of any "typical" load, you've decided to pick the most non-typical one imaginable. and my comments were in response to a a post asking "Why don't manufacturers use a reactive dummy load typical of a real speaker?" My point was and is that there is no "typical" speaker, and I stand by that. Stand as you wish, but your point is not technically supportable. I have constructed 4 such impedance models, based precisely on the pruning model I discussed above, but have further performed measurements on a much wider variety of loads driven by a wide variety of amplifiers. These measurement data all clearly support the assertion that the largets differences is between puerely resistive loading and nearly ANY "typical" speaker impedance, i.e., one that reasonably emulates a two-way or three-way system of moderate of low impedance. Chaning parameters such as moving the systems fundamental resonance from, say, 30 to 50 Hz, or changing it from a sealed box with one impedance peak to a reflex with two and such does nOT substantially change how the amplifier behaves. The exception, of course, being the outlyinh pathological cases, such as amplifiers with extremely high output impedance, and more. But as to the assertion that there can be now "typcial" load? No. |
#226
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Yahama "natural sound" amp specs?
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#227
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Yahama "natural sound" amp specs?
"Pooh Bear" wrote in message ... You further stated, clearly, that: "that the room affects a speaker's overall reactance has been known for many years." Again, I ask, "known by whom?" Well...... I don't think there's any doubt that a speaker cabinet influences the impedance curve is there ? By analogy, clearly the room ( in effect another cabinet in front of the speaker cone ) must have a similar if somewhat rather smaller effect. Just because it can be normally ignored doesn't mean it doesn't exist. In practice of course it's not an issue but the effect must clearly be there at a minute level. But since it *IS* a MINUTE factor, and can be safely ignored in all cases, bringing it up in the thread as something that needs to considered (or at all), would be well and truly classified as a "red herring", or maybe a "straw man", wouldn't you agree? MrT. |
#228
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Yahama "natural sound" amp specs?
"Mr.T" wrote: "Pooh Bear" wrote in message ... You further stated, clearly, that: "that the room affects a speaker's overall reactance has been known for many years." Again, I ask, "known by whom?" Well...... I don't think there's any doubt that a speaker cabinet influences the impedance curve is there ? By analogy, clearly the room ( in effect another cabinet in front of the speaker cone ) must have a similar if somewhat rather smaller effect. Just because it can be normally ignored doesn't mean it doesn't exist. In practice of course it's not an issue but the effect must clearly be there at a minute level. But since it *IS* a MINUTE factor, and can be safely ignored in all cases, bringing it up in the thread as something that needs to considered (or at all), would be well and truly classified as a "red herring", or maybe a "straw man", wouldn't you agree? Depends on context. Since there clearly must be *some* effect, I think it's unreasonable to dismiss it out of hand. Graham |
#229
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Yahama "natural sound" amp specs?
On Fri, 09 Jun 2006 05:08:43 +0100, Pooh Bear
wrote: "Mr.T" wrote: "Pooh Bear" wrote in message ... You further stated, clearly, that: "that the room affects a speaker's overall reactance has been known for many years." Again, I ask, "known by whom?" Well...... I don't think there's any doubt that a speaker cabinet influences the impedance curve is there ? By analogy, clearly the room ( in effect another cabinet in front of the speaker cone ) must have a similar if somewhat rather smaller effect. Just because it can be normally ignored doesn't mean it doesn't exist. In practice of course it's not an issue but the effect must clearly be there at a minute level. But since it *IS* a MINUTE factor, and can be safely ignored in all cases, bringing it up in the thread as something that needs to considered (or at all), would be well and truly classified as a "red herring", or maybe a "straw man", wouldn't you agree? Depends on context. Since there clearly must be *some* effect, I think it's unreasonable to dismiss it out of hand. Since it's effect has been calculated to be less than 0.1% of the only factor (fundamental resonance) that will show any demonstrable effect at all, and since the two drivers in a pair of speakers are unlikely to have their fundamental resonances matched to better than a couple of percent, I think it's *entirely* reasonable to dismiss it out of hand. If you disagree, then we'll have to move on to the equally if not in many cases more significant matters of room temperature and humidity, not to mention altitude and its dramatic effect on air density. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
#230
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Yahama "natural sound" amp specs?
"Stewart Pinkerton" wrote in message
... On Fri, 09 Jun 2006 05:08:43 +0100, Pooh Bear wrote: "Mr.T" wrote: "Pooh Bear" wrote in message ... You further stated, clearly, that: "that the room affects a speaker's overall reactance has been known for many years." Again, I ask, "known by whom?" Well...... I don't think there's any doubt that a speaker cabinet influences the impedance curve is there ? By analogy, clearly the room ( in effect another cabinet in front of the speaker cone ) must have a similar if somewhat rather smaller effect. Just because it can be normally ignored doesn't mean it doesn't exist. In practice of course it's not an issue but the effect must clearly be there at a minute level. But since it *IS* a MINUTE factor, and can be safely ignored in all cases, bringing it up in the thread as something that needs to considered (or at all), would be well and truly classified as a "red herring", or maybe a "straw man", wouldn't you agree? Depends on context. Since there clearly must be *some* effect, I think it's unreasonable to dismiss it out of hand. Since it's effect has been calculated to be less than 0.1% of the only factor (fundamental resonance) that will show any demonstrable effect at all, and since the two drivers in a pair of speakers are unlikely to have their fundamental resonances matched to better than a couple of percent, I think it's *entirely* reasonable to dismiss it out of hand. If you disagree, then we'll have to move on to the equally if not in many cases more significant matters of room temperature and humidity, not to mention altitude and its dramatic effect on air density. There's one case, and only one, where the room volume *may* have an effect, and that's the case of the automobile. And only when the windows are closed. As for "typical" speaker impedances, I think Don has nailed it: you can't design a single dummy load that represents everything, but you can design a few that represent almost everything, and that's good enough for practical purposes. It's like the (male) mathematician who told the (male) engineer that it was mathematically impossible for him to actually come into contact with the luscious (female) graduate student across the room. "No," replied the engineer, "but I can get arbitrarily close, and from a practical point of view that's good enough for me." Peace, Paul |
#231
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Yahama "natural sound" amp specs?
Pooh Bear wrote:
"Mr.T" wrote: "Pooh Bear" wrote in message ... You further stated, clearly, that: "that the room affects a speaker's overall reactance has been known for many years." Again, I ask, "known by whom?" Well...... I don't think there's any doubt that a speaker cabinet influences the impedance curve is there ? By analogy, clearly the room ( in effect another cabinet in front of the speaker cone ) must have a similar if somewhat rather smaller effect. Just because it can be normally ignored doesn't mean it doesn't exist. In practice of course it's not an issue but the effect must clearly be there at a minute level. But since it *IS* a MINUTE factor, and can be safely ignored in all cases, bringing it up in the thread as something that needs to considered (or at all), would be well and truly classified as a "red herring", or maybe a "straw man", wouldn't you agree? Depends on context. Since there clearly must be *some* effect, I think it's unreasonable to dismiss it out of hand. Error bars, man. Think error bars. :-) Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
#232
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Yahama "natural sound" amp specs?
Pooh Bear wrote:
wrote: Again, I ask, "known by whom?" Dick, I am very glad to see you here in rec.audio.pro again. Well...... I don't think there's any doubt that a speaker cabinet influences the impedance curve is there ? By analogy, clearly the room ( in effect another cabinet in front of the speaker cone ) must have a similar if somewhat rather smaller effect. Just because it can be normally ignored doesn't mean it doesn't exist. In practice of course it's not an issue but the effect must clearly be there at a minute level. I actually did do a plot on the NHT A-20 speakers in my new editing room, with the room empty and very live and with the room dead. I could see no difference in the curve that I did at octave intervals with a military ZM-35 bridge good down to 0.1 ohm and a 200CD signal generator, on both the woofer and tweeter. (With the A-20, the crossover is in the amp so it was easier to do the drivers directly). What can I say, I was bored and looking for any excuse to avoid moving more boxes of tapes. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#233
Posted to rec.audio.tech,rec.audio.pro,alt.music.home-studio
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Yahama "natural sound" amp specs?
Pooh Bear wrote: wrote: Mike Rieves wrote: "that the room affects a speaker's overall reactance has been known for many years." Again, I ask, "known by whom?" Well...... I don't think there's any doubt that a speaker cabinet influences the impedance curve is there ? By analogy, clearly the room ( in effect another cabinet in front of the speaker cone ) must have a similar if somewhat rather smaller effect. Excuse me, but a factor of 1,000 is NOT a "somewhat rather smaller effect." Just because it can be normally ignored doesn't mean it doesn't exist. No, it's not that "it can be normally ignored." Given that there are many confounding variables that have at least an order of magnitude greater effect, and no one to date has supplied a single shred of repeatable data to support your assertion, It's reasonable to state that it can be totally ignored. In practice of course it's not an issue but the effect must clearly be there at a minute level. It is most assuredly NOT clearly visible. There are any number of confounding variables, temperature of the spaker components, changes in humidity, driver-to-driver variations, mechanical hysteresis in the surround and spider, so on and so forth, all of which have effects that are AT LEAST and order of magnitude greater. Given all those variations, how could you possible claim that "the effect must clearly be there ate a minute level?" You nor anyone else has presented any actual data to suggest otherwise. And there are any number of effects that are there on a minute level. How many people are concerned with the Hall effect of the charge carriers in the voice coil winding, for example. The effect is "there," it's just that's its not there. |
#234
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Yahama "natural sound" amp specs?
Scott Dorsey wrote: Pooh Bear wrote: wrote: Again, I ask, "known by whom?" Dick, I am very glad to see you here in rec.audio.pro again. Well...... I don't think there's any doubt that a speaker cabinet influences the impedance curve is there ? By analogy, clearly the room ( in effect another cabinet in front of the speaker cone ) must have a similar if somewhat rather smaller effect. Just because it can be normally ignored doesn't mean it doesn't exist. In practice of course it's not an issue but the effect must clearly be there at a minute level. I actually did do a plot on the NHT A-20 speakers in my new editing room, with the room empty and very live and with the room dead. I could see no difference in the curve that I did at octave intervals with a military ZM-35 bridge good down to 0.1 ohm and a 200CD signal generator, on both the woofer and tweeter. (With the A-20, the crossover is in the amp so it was easier to do the drivers directly). What can I say, I was bored and looking for any excuse to avoid moving more boxes of tapes. Fair enough. You've proved the point. I was just nitpicking really. Graham |
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