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haunyack
2007-07-22, 14:37
I've heard this term used with respect to the relationship between amp and speakers.
What does it mean exactly?

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haunyack
2007-07-23, 16:06
bump.

Anyone?

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jeffmeh
2007-07-24, 06:01
I have never heard the term in that context, but I do remember this.

http://en.wikipedia.org/wiki/Acoustic_coupler

mudlark
2007-07-24, 06:20
I've heard this term used with respect to the relationship between amp and speakers.
What does it mean exactly?

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Can you give some context here? The only acoustic coupling that can occur between amp and speaker is if there is some mechanical pickup of sound waves which generates a voltage within the amplifier. The simplistic ways of avoiding this is to keep the amp away from the speakers and to use an amp support system which drains away vibrations from the amp.

Ramage
2007-07-24, 08:04
Can you give some context here? The only acoustic coupling that can occur between amp and speaker is if there is some mechanical pickup of sound waves which generates a voltage within the amplifier. The simplistic ways of avoiding this is to keep the amp away from the speakers and to use an amp support system which drains away vibrations from the amp.

Well explained mudlark. This phenomenon was common in amplifiers using vacuum tubes (valves to those in UK) where the acoustic vibrations from the speakers caused the valve grids to physically modulate the signal and cause feedback effects.

haunyack
2007-07-24, 10:16
Can you give some context here? The only acoustic coupling that can occur between amp and speaker is if there is some mechanical pickup of sound waves which generates a voltage within the amplifier. The simplistic ways of avoiding this is to keep the amp away from the speakers and to use an amp support system which drains away vibrations from the amp.

Thanks for the response.

I read the term concerning speaker wire length.
Apparently, in terms of speaker cable, the shorter the better but too short will cause this acoustic coupling.

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mudlark
2007-07-24, 12:54
Thanks for the response.

I read the term concerning speaker wire length.
Apparently, in terms of speaker cable, the shorter the better but too short will cause this acoustic coupling.

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Sorry haunyack this does not compute with my knowledge memory banks. Interesting thing with the valve setup. clearly a large valve with wobbly innards could be a problem. I have no information about short cables being a problem.

good luck with the research.

M.

haunyack
2007-07-24, 16:12
Sorry haunyack this does not compute with my knowledge memory banks. Interesting thing with the valve setup. clearly a large valve with wobbly innards could be a problem. I have no information about short cables being a problem.

good luck with the research.

M.


I'll try to find the reference and post the info.

Cheers!

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tyler_durden
2007-07-24, 18:21
Short cables are an issue because it implies that the amp is located close to the speakers where it is more likely that sound from the speakers will excite mechanical resonances in the amplifier. Yet another reason to detest tube amps!

Solid state amps generally don't suffer from this problem, however, there are many golden ears who claim to hear such problems even with solid state amps and need to spend vast sums on equipment racks to ameliorate the problem.

TD

haunyack
2007-07-25, 07:59
ameliorate the problem.

TD


$64,000 word worthy of the audiophile forum.

Still cannot remember where I read that term ... oh well - memory the 3rd thing to go, don't remember the 1st & 2nd.

Thanks TD

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pfarrell
2007-07-25, 20:13
Yes, Tube(valve) amps have serious problems with this because nearly all tubes are, or can become, microphonic. Microphonic is the term of art to describe when physicially shaking the tube causes it to act as a microphone. Very bad in general for audio quality.

Turntables, remember them? have always had problems with acoustic coupling, either from heavy feet clomping as they dance, or speakers causing the turntable to vibrate in sync.



Solid state amps generally don't suffer from this problem, however, there are many golden ears who claim to hear such problems even with solid state amps and need to spend vast sums on equipment racks to ameliorate the problem.



There is a slightly more plausible case that CD players could be subject to vibrations, moving parts and all that. I think, IMHO, etc. that this is unlikely and approaches snake oil.

Anyone claiming that interconnects or speaker cables are susceptible to this are selling vastly overpriced snake oil.



ameliorate the problem.


Eschew obfuscation

Mark Lanctot
2007-07-26, 05:47
Apparently, in terms of speaker cable, the shorter the better but too short will cause this acoustic coupling.

I think what was meant here was that if the cable was so short that it was taut like a string, it could transmit vibrations.

Sounds like snake oil to me and also sounds not quite possible to do but this is the only way a flexible cable can transmit considerable mechanical force.

aubuti
2007-07-26, 06:19
Or maybe that the cable is so short that the only place to put the amp is on top of (or underneath!) the speaker ;)

haunyack
2007-07-26, 07:14
It's reasonable to assume that the term implies mechanical interference as some have stated.

Although my speaker cables are only 1.5 meter, the speakers are spiked and the amp is well isolated.

So, I suppose I should not worry about the acoustic coupling and spend my time considering the terms 'Eschew obfuscation, amelioration' , contemplate my navel, and of course, listen to the music.

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