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#41
Posted to rec.audio.high-end
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speaker efficiency
On Sat, 3 Nov 2007 11:39:34 -0700, Arny Krueger wrote
(in article ): "Sonnova" wrote in message ... On Thu, 1 Nov 2007 16:08:10 -0700, Arny Krueger wrote (in article ): "Sonnova" wrote in message ... Simple. Hook a bookshelf speaker system rated at "200 watts" to a 25 Watt/channel Wiliamson amplifier and notice that it keeps blowing tweeters (and is not oscillating). The bookshelf tweeter probably has a real-world (not spec sheet) power capacity of under 10 watts. Most tweeters are like that, Not these days, not in quality speakers. Please see my other recent post on the matter. that's (one reason) why they have at least a capacitor in series with them The capacitor is a part of a filter that routes lows to the woofer and highs to the tweeters in the interest of smooth response. Actually, it's purpose is to keep low frequency (and thus large, low-frequency voltage swings) out of the somewhat fragile tweeters rather than to route high frequencies to the tweeter - although it does that. and sometimes a fuse. Or other part like a light bulb that protects the tweeter from abuse. Lightbulbs are very nonlinear devices and I would think that they would act more like a compressor than anything else. I can't imagine that this solution would sound all that good, but you're right, it would work because as the filament heated-up, it's impedance would rise. The fuse doesn't usually blow in these cases because the cooked tweeter is not due to excess current, but rather because it's voice-coil duty cycle has been continuously exceeded by a clipping amplifier. Excess current and exceeding the duty cycle are two ways of describing the identical same process. Not exactly. With duty cycle we are dealing with an average amount of AC current over time, with a fuse we are dealing with peak current, usually instantaneous (most speaker protection fuses tend to be fast-blow variety). It is very possible, even probable that a puny amplifier will be unable to pump out enough current to blow a fuse, but in hard clipping can continually energize the voice coil of a small speaker like a tweeter, not giving it time to cool-off between cycles. in such a case, said tweeter overheats and burns out. All of this without once blowing the fuse. Ferro-fluid in the voice-coil gap has reduced this phenomenon in most better speaker systems these days, and most no longer suffer this indignity. I know a guy who once was powering a pair of Magnapan MG-3s (no letter suffix) with a Dyna Stereo 70. It sounded fine, but he kept blowing the Maggies' ribbon tweeters. Once, while talking to a tech at the Magnapan factory about this, the tech noticed that he had replaced tweeters in his MG-3's several times. He asked the guy about his peripheral equipment. When our audiophile mentioned the ST-70, the tech told him that that was the problem. The amp was blowing the tweeter because it was too small (I had told him the same thing) and he recommended that the guy replace the amp with something bigger - on the order of at least 100 Watts/channel. He did so by replacing the Dyna with an ADCOM GFA-5500 (200 W/PC) and never blew another tweeter. I bought his ST-70 and use it to this day with a pair of Polk bookshelf speakers connected to my computer. It's fine for that application. BTW, I too had a pair of Maggie's; MG-3B's in my case, running off of my VTL 140's. I never once blew a tweeter and I had those speakers for 12 years. |
#42
Posted to rec.audio.high-end
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speaker efficiency
"Sonnova" wrote in message
... I know a guy who once was powering a pair of Magnapan MG-3s (no letter suffix) with a Dyna Stereo 70. It sounded fine, but he kept blowing the Maggies' ribbon tweeters. Once, while talking to a tech at the Magnapan factory about this, the tech noticed that he had replaced tweeters in his MG-3's several times. He asked the guy about his peripheral equipment. When our audiophile mentioned the ST-70, the tech told him that that was the problem. The amp was blowing the tweeter because it was too small (I had told him the same thing) and he recommended that the guy replace the amp with something bigger - on the order of at least 100 Watts/channel. Isn't the problem here that these speakers of are _both_ low efficiency and low impedance? Can't any "high current" 100 watt amp can drive these speakers more easily to high volumes, without clipping, blowing fuses and/or damaging the ribbons than can any garden variety 200 Watt/channel amp? He did so by replacing the Dyna with an ADCOM GFA-5500 (200 W/PC) and never blew another tweeter. Adcom amps are famed for their ability to drive LOW impedance loudspeakers. (Before switching to Bryston monoblocs, I succeeded in driving a pair of Tympani IVa with a pair of bridged Adcom GFA 555 without incident for many years.) I bought his ST-70 and use it to this day with a pair of Polk bookshelf speakers connected to my computer. It's fine for that application. BTW, I too had a pair of Maggie's; MG-3B's in my case, running off of my VTL 140's. I never once blew a tweeter and I had those speakers for 12 years. |
#43
Posted to rec.audio.high-end
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speaker efficiency
On Sun, 4 Nov 2007 10:14:07 -0800, Norman M. Schwartz wrote
(in article ): "Sonnova" wrote in message ... I know a guy who once was powering a pair of Magnapan MG-3s (no letter suffix) with a Dyna Stereo 70. It sounded fine, but he kept blowing the Maggies' ribbon tweeters. Once, while talking to a tech at the Magnapan factory about this, the tech noticed that he had replaced tweeters in his MG-3's several times. He asked the guy about his peripheral equipment. When our audiophile mentioned the ST-70, the tech told him that that was the problem. The amp was blowing the tweeter because it was too small (I had told him the same thing) and he recommended that the guy replace the amp with something bigger - on the order of at least 100 Watts/channel. Isn't the problem here that these speakers of are _both_ low efficiency and low impedance? Can't any "high current" 100 watt amp can drive these speakers more easily to high volumes, without clipping, blowing fuses and/or damaging the ribbons than can any garden variety 200 Watt/channel amp? Sure, they are fairly low efficiency (88dB/Watt/meter, IIRC), but they aren't particularly low impedance. But 35-watts/channel is simply too small of an amplifier and it spent a lot of time in clipping - especially on rock music. He did so by replacing the Dyna with an ADCOM GFA-5500 (200 W/PC) and never blew another tweeter. Adcom amps are famed for their ability to drive LOW impedance loudspeakers. (Before switching to Bryston monoblocs, I succeeded in driving a pair of Tympani IVa with a pair of bridged Adcom GFA 555 without incident for many years.) Maggies are a very easy load. Most are 6 ohms and it's almost totally resistive. Speaking of the Magneplanar line of Tympani loudspeakers, I once had a pair of Tympani IIIc (all SIX panels) that I powered with a Hafler 101 amp on the midrange/top and a Marantz transistor amp (don't remember the model number) on the bass panels. Never had any trouble with them or the amplifiers with which I was driving them. What finally made me replace the Tympanis was that Magneplanar used to use an adhesive to glue the voice grid to the Mylar diaphragms which was reactive with ultraviolet light. I had the speakers down at the open end of the living room (these speakers took up a LOT of room and ended up being 9 ft X 7 ft fully expanded) where they were near the sliding patio door. On nice days, I'd open the patio doors to let air circulate through the house and sunlight would stream through the screen door and hit the Maggies. Over time, this broke the glue down into a substance that actually attacked the voice-grid wires (which were aluminum) of the tweeter and midrange panels nearest the door and ate through them! Magneplanar wanted me to send the entire speaker system back to them to be refurbished and by the time I would have spent the money to order a couple of shipping crates from Magneplanar, paid the freight, and the fee they wanted to rebuild the speakers, I was more than 3/4 of the way to a new pair of MG-3Bs. I sold the Tympani's to a guy who thought that getting them refurbished was a bargain, and I bought the MG-3Bs. I have Martin-Logan electrostatics now, but would dearly love to have a pair of Magnepan MG-20s. I bought his ST-70 and use it to this day with a pair of Polk bookshelf speakers connected to my computer. It's fine for that application. BTW, I too had a pair of Maggie's; MG-3B's in my case, running off of my VTL 140's. I never once blew a tweeter and I had those speakers for 12 years. |
#44
Posted to rec.audio.high-end
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speaker efficiency
"Sonnova" wrote in message
... On Sun, 4 Nov 2007 10:14:07 -0800, Norman M. Schwartz wrote (in article ): "Sonnova" wrote in message ... I know a guy who once was powering a pair of Magnapan MG-3s (no letter suffix) with a Dyna Stereo 70. It sounded fine, but he kept blowing the Maggies' ribbon tweeters. Once, while talking to a tech at the Magnapan factory about this, the tech noticed that he had replaced tweeters in his MG-3's several times. He asked the guy about his peripheral equipment. When our audiophile mentioned the ST-70, the tech told him that that was the problem. The amp was blowing the tweeter because it was too small (I had told him the same thing) and he recommended that the guy replace the amp with something bigger - on the order of at least 100 Watts/channel. Isn't the problem here that these speakers of are _both_ low efficiency and low impedance? Can't any "high current" 100 watt amp can drive these speakers more easily to high volumes, without clipping, blowing fuses and/or damaging the ribbons than can any garden variety 200 Watt/channel amp? Sure, they are fairly low efficiency (88dB/Watt/meter, IIRC), but they aren't particularly low impedance. But 35-watts/channel is simply too small of an amplifier and it spent a lot of time in clipping - especially on rock music. He did so by replacing the Dyna with an ADCOM GFA-5500 (200 W/PC) and never blew another tweeter. Adcom amps are famed for their ability to drive LOW impedance loudspeakers. (Before switching to Bryston monoblocs, I succeeded in driving a pair of Tympani IVa with a pair of bridged Adcom GFA 555 without incident for many years.) Maggies are a very easy load. Most are 6 ohms and it's almost totally resistive. Speaking of the Magneplanar line of Tympani loudspeakers, I once had a pair of Tympani IIIc (all SIX panels) that I powered with a Hafler 101 amp on the midrange/top and a Marantz transistor amp (don't remember the model number) on the bass panels. Never had any trouble with them or the amplifiers with which I was driving them. IIIc 6 panels?; Tympani 1 series are 6 panels (e.g., IU, IC (both 8 ohms, ID). 8 panels are the tympani III series, tympani III, 8 ohms and tympani IIIB (4 ohms). I had tympani IIIB (all EIGHT panels), 4 ohms impedance and neither a "200" watt amp, (GAS Ampzilla II) nor a 75 watt tube amp (ARC D-76a) could drive either the tweeter or mid range panels without clipping. Piano chords are especially demanding of watts and current. What finally made me replace the Tympanis was that Magneplanar used to use an adhesive to glue the voice grid to the Mylar diaphragms which was reactive with ultraviolet light. I had the speakers down at the open end of the living room (these speakers took up a LOT of room and ended up being 9 ft X 7 ft fully expanded) where they were near the sliding patio door. On nice days, I'd open the patio doors to let air circulate through the house and sunlight would stream through the screen door and hit the Maggies. Over time, this broke the glue down into a substance that actually attacked the voice-grid wires (which were aluminum) of the tweeter and midrange panels nearest the door and ate through them! I had Tympani ICs (6panels!) and UV in skylight coming through closed windows broke down that adhesive! (At least that's what Magnepan informed could, would and did happen), and BTW having the cartons for these Tympanis, I DID have them refurbished; the tweeters were replaced (too far damaged) and everything with the UV-resistant resistant glue. Magneplanar wanted me to send the entire speaker system back to them to be refurbished and by the time I would have spent the money to order a couple of shipping crates from Magneplanar, paid the freight, and the fee they wanted to rebuild the speakers, I was more than 3/4 of the way to a new pair of MG-3Bs. I sold the Tympani's to a guy who thought that getting them refurbished was a bargain, and I bought the MG-3Bs. I have Martin-Logan electrostatics now, but would dearly love to have a pair of Magnepan MG-20s. I bought his ST-70 and use it to this day with a pair of Polk bookshelf speakers connected to my computer. It's fine for that application. BTW, I too had a pair of Maggie's; MG-3B's in my case, running off of my VTL 140's. I never once blew a tweeter and I had those speakers for 12 years. |
#45
Posted to rec.audio.high-end
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speaker efficiency
On Sun, 4 Nov 2007 19:25:24 -0800, Norman M. Schwartz wrote
(in article ): "Sonnova" wrote in message ... On Sun, 4 Nov 2007 10:14:07 -0800, Norman M. Schwartz wrote (in article ): "Sonnova" wrote in message ... I know a guy who once was powering a pair of Magnapan MG-3s (no letter suffix) with a Dyna Stereo 70. It sounded fine, but he kept blowing the Maggies' ribbon tweeters. Once, while talking to a tech at the Magnapan factory about this, the tech noticed that he had replaced tweeters in his MG-3's several times. He asked the guy about his peripheral equipment. When our audiophile mentioned the ST-70, the tech told him that that was the problem. The amp was blowing the tweeter because it was too small (I had told him the same thing) and he recommended that the guy replace the amp with something bigger - on the order of at least 100 Watts/channel. Isn't the problem here that these speakers of are _both_ low efficiency and low impedance? Can't any "high current" 100 watt amp can drive these speakers more easily to high volumes, without clipping, blowing fuses and/or damaging the ribbons than can any garden variety 200 Watt/channel amp? Sure, they are fairly low efficiency (88dB/Watt/meter, IIRC), but they aren't particularly low impedance. But 35-watts/channel is simply too small of an amplifier and it spent a lot of time in clipping - especially on rock music. He did so by replacing the Dyna with an ADCOM GFA-5500 (200 W/PC) and never blew another tweeter. Adcom amps are famed for their ability to drive LOW impedance loudspeakers. (Before switching to Bryston monoblocs, I succeeded in driving a pair of Tympani IVa with a pair of bridged Adcom GFA 555 without incident for many years.) Maggies are a very easy load. Most are 6 ohms and it's almost totally resistive. Speaking of the Magneplanar line of Tympani loudspeakers, I once had a pair of Tympani IIIc (all SIX panels) that I powered with a Hafler 101 amp on the midrange/top and a Marantz transistor amp (don't remember the model number) on the bass panels. Never had any trouble with them or the amplifiers with which I was driving them. IIIc 6 panels?; Tympani 1 series are 6 panels (e.g., IU, IC (both 8 ohms, ID). 8 panels are the tympani III series, tympani III, 8 ohms and tympani IIIB (4 ohms). I had tympani IIIB (all EIGHT panels), 4 ohms impedance and neither a "200" watt amp, (GAS Ampzilla II) nor a 75 watt tube amp (ARC D-76a) could drive either the tweeter or mid range panels without clipping. Piano chords are especially demanding of watts and current. You are correct. I miss-remembered, the IIIs did have EIGHT panels, the bass panels for each channel were doubled-up (4) and then one each on both sides for midrange and tweeter panels. After all, it's been more than 20 years! However, I had no problem driving these speakers with the Hafler 101 and the 200W/channel Marantz, but then my listening room wasn't all that big (14 X 16 or thereabouts). What finally made me replace the Tympanis was that Magneplanar used to use an adhesive to glue the voice grid to the Mylar diaphragms which was reactive with ultraviolet light. I had the speakers down at the open end of the living room (these speakers took up a LOT of room and ended up being 9 ft X 7 ft fully expanded) where they were near the sliding patio door. On nice days, I'd open the patio doors to let air circulate through the house and sunlight would stream through the screen door and hit the Maggies. Over time, this broke the glue down into a substance that actually attacked the voice-grid wires (which were aluminum) of the tweeter and midrange panels nearest the door and ate through them! I had Tympani ICs (6panels!) and UV in skylight coming through closed windows broke down that adhesive! (At least that's what Magnepan informed could, would and did happen), and BTW having the cartons for these Tympanis, I DID have them refurbished; the tweeters were replaced (too far damaged) and everything with the UV-resistant resistant glue. IIRC, that they wanted something like $250 for a set of crates, another $300 for round-trip shipping by truck and something like $1200 to rebuild them. They did say that the rebuild included new tweeter panels, new Mylar diaphragms all-round and that they had changed to a new adhesive for the voice-grid wires that was not sensitive to UV. I do remember the name of the guy I dealt with at Magneplanar because it was, what I thought, an unusual name: Wendell Diller. |
#46
Posted to rec.audio.high-end
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speaker efficiency
"Sonnova" wrote in message
... either the tweeter or mid range panels without clipping. Piano chords are especially demanding of watts and current. You are correct. I miss-remembered, the IIIs did have EIGHT panels, the bass panels for each channel were doubled-up (4) and then one each on both sides for midrange and tweeter panels. After all, it's been more than 20 years! However, I had no problem driving these speakers with the Hafler 101 and the 200W/channel Marantz, but then my listening room wasn't all that big (14 X 16 or thereabouts). Well, we have come full circle here. Your IIIs, just as all the Tympanis, up to the 1C, were both low efficiency _AND_ of 8 ohm ("purely resistive") impedance. That's why the were/are comfortably driven by your amps and well as my Audio Reseach Corporation tubed D-76As (75 watts). Then came the Tympani IIIB, the 1D, the IV and IVa; their impedance was decreased. Reading from my Tympani IVa manual; Bass--4ohms, Midrange and ribbon tweeter--3ohms. These low impedance loads "suck" the current out of those Hafler amps (as they did all of mine) and most of the amps of their day. Having attempted it I can testify to the fact that one needs a "high current" amp to drive today's big Maggies. I do successfuly drive their baby SMG to loud volumes in a secondary system in a very large room with the 200 watt Ampzilla II, blowing no fuses (neither amp nor speaker), nor destroy speaker drivers. IIRC, that they wanted something like $250 for a set of crates, I stored mine. (The "crates", being the cartons they were delivered in.) another $300 for round-trip shipping by truck and something like $1200 to rebuild them. They did say that the rebuild included new tweeter panels, new Mylar diaphragms all-round and that they had changed to a new adhesive for the voice-grid wires that was not sensitive to UV. I do remember the name of the guy I dealt with at Magneplanar because it was, what I thought, an unusual name: Wendell Diller. I provided the receipt for the rebuild of my Tympani 1C to the person I sold them to, so I can't quote my cost. (Shipping those 8 panels is more costly than 6 panels.) I was very pleased with my rebuilt speakers, they both looked and sounded better than new, everything was new including the terminals. As I spoke to him via telephone about 6 months ago, I can testify that Mr.Diller was still working there. Magnepan's customer support is outstanding as is their repairs department. They deserve every ounce of the high regard in which they are held. |
#47
Posted to rec.audio.high-end
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speaker efficiency
On Tue, 6 Nov 2007 16:03:40 -0800, Norman M. Schwartz wrote
(in article ): "Sonnova" wrote in message ... either the tweeter or mid range panels without clipping. Piano chords are especially demanding of watts and current. You are correct. I miss-remembered, the IIIs did have EIGHT panels, the bass panels for each channel were doubled-up (4) and then one each on both sides for midrange and tweeter panels. After all, it's been more than 20 years! However, I had no problem driving these speakers with the Hafler 101 and the 200W/channel Marantz, but then my listening room wasn't all that big (14 X 16 or thereabouts). Well, we have come full circle here. Your IIIs, just as all the Tympanis, up to the 1C, were both low efficiency _AND_ of 8 ohm ("purely resistive") impedance. That's why the were/are comfortably driven by your amps and well as my Audio Reseach Corporation tubed D-76As (75 watts). Then came the Tympani IIIB, the 1D, the IV and IVa; their impedance was decreased. Reading from my Tympani IVa manual; Bass--4ohms, Midrange and ribbon tweeter--3ohms. These low impedance loads "suck" the current out of those Hafler amps (as they did all of mine) and most of the amps of their day. Having attempted it I can testify to the fact that one needs a "high current" amp to drive today's big Maggies. I do successfuly drive their baby SMG to loud volumes in a secondary system in a very large room with the 200 watt Ampzilla II, blowing no fuses (neither amp nor speaker), nor destroy speaker drivers. IIRC, that they wanted something like $250 for a set of crates, I stored mine. (The "crates", being the cartons they were delivered in.) another $300 for round-trip shipping by truck and something like $1200 to rebuild them. They did say that the rebuild included new tweeter panels, new Mylar diaphragms all-round and that they had changed to a new adhesive for the voice-grid wires that was not sensitive to UV. I do remember the name of the guy I dealt with at Magneplanar because it was, what I thought, an unusual name: Wendell Diller. I provided the receipt for the rebuild of my Tympani 1C to the person I sold them to, so I can't quote my cost. (Shipping those 8 panels is more costly than 6 panels.) I was very pleased with my rebuilt speakers, they both looked and sounded better than new, everything was new including the terminals. As I spoke to him via telephone about 6 months ago, I can testify that Mr.Diller was still working there. Magnepan's customer support is outstanding as is their repairs department. They deserve every ounce of the high regard in which they are held. Oh, I agree, but these days I'm real happy with my Martin-Logan Vantages. |
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