Please explain amplifier output impedance

Duke notes:

It took me a very long time to get the impedance curves smooth enough that there wasn't a significant tonal balance difference depending on which amp I used. Easy to smooth the impedance curves, but hard to do so without screwing something else up

Indeed it is! How did you go about it --if I'm not asking a sensitive question? Cheers

Duke: I don't need to tell you or anyone else that has truly dug deeply into designing / building a great speaker that the amount of work / R & D ( research & development ) that one can put into such a project can be mind-boggling. The things that make an audible difference are too high to count, let alone factoring in how to manipulate exactly which "mods" or "tweaks" to use in conjunction with others. Obviously, there are a LOT of design variables and personal decisions to be made when arriving at the final product. Even then, with most DIY speakers, that final product is typically NOT "final" by any means.

Having said that, it amazes me at what some of these manufacturers produce, market and settle for at the prices that they charge. Same thing goes for Pro Sound reinforcement and guitar / bass cabinets. These are typically low to medium grade drivers stuffed into a poorly built and designed box using whatever low grade wiring and hardware that they can find. Sean
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* For those that can't do the math, an output impedance of .2 ohm would produce a damping factor of 40 as referenced to an 8 ohm speaker. This would be an acceptable starting point for someone trying to drive a larger woofer with a decent sized motor structure. Smaller diameter woofers with smaller motors and / or limited excursion might get away with a slightly lower DF ( damping factor ) without any really noticeable problems.

Much earlier in this thread I suggested 80 as an "ideal" damping factor or 0.1 Ohm output impedance as a good number to seek for a nominal 8 Ohm speaker load (not too much negative feedback and not too lacking in linearity/control when coupled with a speaker).

I can also live with Sean's very close suggestion above. I think, at least for once, we are reaching a consensus on your question Tvad; you have your "Goldilock's" answer as to what may be considered too low, too high and "just right" for amplifier output impedance in relation to load.

Of course, I hope everyone understands that this is a huge generalization that applies to SS amps and I would never recommend choosing one component over another based on this criteria alone.

Success! And in only six days...

:)

Success? I would consider damping over 20:1 to be excessive. I use master tapes for reference and one thing has become clear over the years: high damping factor equates to not getting the bass right; retentive (not in a good way) IOW punch without real definition and the first thing to go is always low frequency ambience.

Some speakers are intentionally designed for amps of higher output impedance (new paradigm, BTW) in order to take advantage of the benefits such amps offer. IOW there is no *ideal* value for output impedance- it all depends on the speaker...

The lesson here is that you have to pay attention to the speaker/amplifier interface regardless of the amplifier or speaker that you have chosen. To ignore this means you could flush thousands of dollars away to no good effect.