4-ohm setting with 8 ohm speakers

Which relates to damping factor. Yes?

A 4 ohm setting increases the impedence that the amplifier sees relative to an 8 ohm setting. Therefore, fewer demands are placed on the amplifier and therefore if the 8 ohm setting is too demanding for the amp it will sound better on a 4 ohm setting. The principle is the one that applies to Paul Speltz's automformers which increase the impedence that the amp sees and will improve the amp's performance up to the point where the impedence is great enough so that it limits the potential of the amp. It's a matter of matching amp to speakers. A more muscular amp than the ones you have auditioned might reach its potential better on the 8 ohm setting. It's an interesting and instructive excercise.

Plato, then what is the purpose of a 4 ohm-8 ohm option on an amplifier? Lynne

The manufacturer's claims of the Nightingale speakers and the difference in quality between the 4-ohm/8ohm settings on amps so equipped are separate issues since these taps affect the sound quality driving any speaker. As a user, sound quality is the whole point for me.

I have a problem with manufacturer's using taps for reasons other than sound quality (in SS. Have no experience with tubes). Skip the taps and design it to perform well under varying conditions for about 20 years. That's just me and yet another issue not related to the question.

Rrog, An example in ss amps is the Harman Kardon amp(s) in the Citation series years ago when hk abandoned their decent quality American-made amps for the Japanese-made lower quality amps after they bought Levinson. Not that there's anything wrong with Japanese-made per say. I think their 4-8ohm taps were to compensate for a less muscular amp that could not handle a 4 ohm load except at the expense of sound quality. And I think this device in ss is sometimes used to compensate for an anemic amp. I'm always suspicious when I see this device in ss, but I realize it has its place. My predjudice also comes from my dislike of switches which degrade sound quality.
I apparently didn't articulate my initial point very well because I surely don't have anything against using the tap that sounds the best as long as it doesn't cause damage to the amp. That's kinda the whole point of the tap. I don't have a technical background as some of you know, but I do understand in general impedence matching of amp and speakers. There is an optimum load for every amp. That is the point of the taps and the point of autoformers, a device used to find that optimum load. Lynne

Magfan, looks interesting. Do you know any reviews in which it has been used?

I'm dyslexic and don't read a lot of tests, but the plain ol' resister doesn't sound good.