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Amplifier And Loudspeaker Interaction

Wombat

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Any available published references on this topic?
 

Blumlein 88

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ESL's like tubes.

Horns like tubes.

Coffins like solid state.

Class D amps suck.

All you need to know.

:D
 

DonH56

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Purité Audio

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You really need to know your speakers impedance over frequency, and how the output of the amp varies into higher impedance loads.
Although often neither amplifier nor speaker manufacturers publish any measurements and if they do they are invariably’nominal’.
Go for active loudspeakers, then you no longer have to worry.
Keith
 

fas42

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You really need to know your speakers impedance over frequency, and how the output of the amp varies into higher impedance loads.
Although often neither amplifier nor speaker manufacturers publish any measurements and if they do they are invariably’nominal’.
Go for active loudspeakers, then you no longer have to worry.
Keith
Agree on active speakers - most power amplifiers are not engineered well enough to do the job of driving typical multi-way speakers competently, no matter what the specs say. A key exception I came across was a Bryston, which performed admirably - a reference in performance capability, for me.
 

restorer-john

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Kenwood in the 1970s spent a lot of time and effort studying it and the results were DC-daylight amplifiers with ultra short, heavily braided/woven special cables and monoblocks placed right next to the speakers. They also pursued 'Sigma Drive' which essentially put the speaker cable in the feedback loop.

Yamaha pursued 'Active Servo Technology' (AST) which put the speaker in the feedback loop and lifted it from ground, thereby essentially creating a 'negative impedance' drive and also employed cartridges (like an Atari game cartridge) that compensated for the impedance/phase characteristics of the attached speakers. Each 'AST' speaker had a basic crossover and the combination of the individual supplied cartridge and the 'negative impedance' drive gave us small speakers that performed incredibly well. Integrated amplifiers with AST came with a 'flat' cartridge for normal speakers.

Sadly, AST died in the marketplace in about 18 months or less.
 
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Wombat

Wombat

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Kenwood in the 1970s spent a lot of time and effort studying it and the results were DC-daylight amplifiers with ultra short, heavily braided/woven special cables and monoblocks place right next to the speakers. They also pursued 'Sigma Drive' which essentially put the speaker cable in the feedback loop.

Yamaha pursued 'Active Servo Technology' (AST) which put the speaker in the feedback loop and lifted it from ground, thereby essentially creating a 'negative impedance' drive and also employed cartridges (like an Atari game cartridge) that compensated for the impedance/phase characteristics of the attached speakers. Each 'AST' speaker had a basic crossover and the combination of the individual supplied cartridge and the 'negative impedance' drive gave us small speakers that performed incredibly well. Integrated amplifiers with AST came with a 'flat' cartridge for normal speakers.

Sadly, AST died in the marketplace in about 18 months or less.


The V-Fet had a short life also, unfortunately.
 

Dilliw

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Example of how a professional loudspeaker designer approaches the question of amplification technology:

https://www.genelec.com/sites/default/files/media/About Us/Academic_Papers/2013_rose.pdf

This paper was written in 2013. Since then there have been no improvements in AB technologies yet there have been significant gains in terms of costs/form factor/power consumption and output quality in Class D. Just released this year are commercial chips that can output without the distortion rise in higher frequencies and can stay stable at any load. Boutique chips could have done it back in 2013 for this test. As Nelson Pass stated in Stereophile we are at the end of science for amplification save the gains that Class D can bring us in terms of cost, form factor, and power consumption. The rest is art.
 

DonH56

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What paper?

Class D designs without many of the issues that plagued the earlier designs have been around a number of years now.

Any amplifier has rising distortion and output impedance with frequency because loop gain and bandwidth are not infinite. Not just a problem for class D, although low switching frequencies and stability issues generally make it a larger problem for class D than typical AB amplifiers. I would not say definitively any given class D amp is better or worse than all other amps; too many variables.
 
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