This is a question - amp speaker interface

[Jorge]

Hello,

In another thread there were many posts re distortion caused in the amp - speaker interface, AKA 'Back EMF'.

The main doubt is how much speaker distortion is objectable?

Well, it's possibe to place any driver (NOT a speaker system) inside a NFB loop and listen to it.
Say one channel of a stereo amp is a plain channel, the other one will receive external components (some minor internal changes) to aplly NFB to the speaker.
Then one can compare one channel to the other.

If there is some interest, I can write an article (a frew posts due to size).
It's based in an old motional feedback technique, does not requires dual voice coil speakers or transducers/microphones.

Note: This would not be a beginner's project, the adjustments to be made for each specific driver requires measurement capability for speaker acoustic response, basic electronic knowledge and a lot of adjustment time.
A good, fairly high power amp is also needed to drive the speaker (placed in a correctly calculated closed box - not ported) to acceptable levels - not 'realistic listening levels'.

But one would be able to listen to one's favorite speaker (a good bass/mid) and do a compare.