@thespeakerdude It doesn’t seem like a very hard problem to create a spreadsheet about speaker drivers, amplifiers, crossovers, cables, etc. and come out with a compatibility number. I understand the changing variables and functions of curves associated with speakers but it’s not that hard.
To have such a list, there would need to be variables associated with each component. I would challenge anyone to come up with the variables for that list. They would start with resistance in some form; amplifier output resistance, cable resistance, speaker input resistance (impedance over frequency). Then they would sit for hours trying to come up with a second quantifiable variable. Maybe they would add a check box column for compatibility; some amplifiers do not like very low impedance speakers.
Most solid state amplifiers will behave the same no matter what speaker you connect them to. Most tube amplifiers will behave differently for every speaker you connect them to. Amplifier/speaker "compatibility" is a losing/loose proposition that may by luck improve a speaker/room issue by a small measure that could have been definitively solved by much better methods. The distortion mechanism of tubes is a wild card. Speakers are never independent of rooms. I don’t think a compatibility score is possible as the speaker room interaction could negate any result you arrive at.
For headphones, I have seen specialized amplifiers for specific headphones, and only those headphones. They implement custom equalization for that headphone.
Apparently the tube amplifier with headphones shtick is similar to the tube amplifier with speakers shtick. Tube amplifiers for headphones are much higher output resistance than SS amplifiers. OTL tube amplifiers like their speaker counterparts are very high output resistance. Depending on the headphone, that is a large change in the frequency response. Headphones are all over the place with frequency response. Not hard to see a tube amplifier often resulting in an improved frequency response.
