Some amplifiers will sound "bright" with some speakers, because of the interaction between the amplifier and speaker. You don't seem to get the basic engineering principles involved.
The simplest reason for this would be because the speaker has relatively high impedances at the upper-midrange frequencies (which is not uncommon) and the amplifier does not have a low-enough output impedance to avoid "going along for the ride' and putting out more voltage at those frequencies in response to the higher impedance load it is seeing; hence the "bright sound"; more output at those frequencies.
A much larger amplifier (bigger power supply hence lower output impedance) will be affected a lot less than a smaller one, and so the "brightness' of the speaker response will be minimized. The combination of the same speaker with the bigger amplifier "sounds better" because the amplifier exerts more "control" and maintains a more constant output in response to the impedance variations of the speaker.
Starting to get the idea yet??
The speakers with the best sound at a modest price point tend to be those with a very constant impedance over the audio frequency range, but very few speakers do. It is certainly instructive to look at the impedance versus frequency graph before thinking about buying a speaker.
It also follows that a relatively smaller amplifier will do a better job with speakers that don't have huge impedance variations, and do a poorer job when the speaker's impedance varies a lot over the audio range.
If your speakers have a lot of variation in their impedance, they may not sound very good unless you have a very powerful high-current amplifier with a very low output impedance that can keep their imperfections under control.
Once again; to speak of a "bright" amplifier or "bright" speaker displays a lack of fundamental understanding of what is taking place.
The COMBINATION of a given amplifier and speaker is what produces a given sound characteristic; the SYNERGY between them is what produces a certain sound quality.
The cheap amplifiers and small power supplies in most HT receivers will only sound good with a very limited number of speakers that have relatively high impedances at ALL frequencies. When people try to use other kinds of speakers the result is poor sound quality. This is a common issue that hardly anyone seems to understand.
Edited by commsysman - 4/20/13 at 10:24am
Originally Posted by Brownstone322
If Simaudio amps were audibly "bright," then that would be obvious from test measurements. VERY obvious. I'll think you'll find their response to be flat.
Meanwhile, NAD amps produce no more bass than any other modern solid-state amp, although they generally deliver lots of power relative to their ratings, which might matter some of the time (high levels, large rooms, low-sensitivity speakers).
I seriously doubt, under honest, objective conditions, that you'd be able to tell a Simaudio amp from any other solid-state amp kept within its operating limits. Why would you be able to?