@atmasphere --
...
I have a lower powered Radio Shack amp that sounds fine as long as you don’t push it hard. It tends to make the 2nd harmonic as its primary distortion product and that masks a good deal of the higher orders. But at higher volume levels there isn’t enough lower ordered content to mask anymore- and so it gets harsh. But if I run speakers that have enough efficiency, the amp never gets to those volumes and it sounds fine.
Put another way, even though a lot of the amps mentioned so far can make quite a bit of power, matching the speaker to them (using an easier to drive speaker) is paramount to getting the most out of them.
Interesting info (not quoted) re: feedback. Apart from the traits of an easier-to-drive speaker with higher impedance load (i.e.: >8 ohms), benign phase angles and high to very high efficiency, getting rid of a passive cross-over is another vital measure to ensure the amp(s) is seeing an easier load, even lessening its importance the same way higher speaker impedance render cables less important.
I’d even wager much of the (in my view) ludicrous tendency of over-built (and insanely expensive) amps from the likes of D’Agostino, Boulder and others are a symptom of the heavy load they’re presented with, and how they strive to be less affected by it (until thermal issues will arise in the speaker). Complex passive cross-overs are very much to blame for this, effectively making a rated, limited sensitivity somewhat of a variable (i.e.: potentially lower) - depending on the amp driving it; one that is more or less impervious to load will see the speaker deliver closer to its full potential at its rated sensitivity (insofar it’s correct to begin with), whereas an amp that is not will obviously hinder a speaker’s performance and its clean dynamic range.
My 30 watt pure Class-A Belles SA30 is coupled directly to a pair of EV compression driver + horn combo with 111dB sensitivity (8 ohm version) - covering from ~600Hz on up. So, there’s another factor to consider: the range a given amp is going to cover. The Belles is practically freed from anything below ~600Hz - again, coupled directly to the CD without any intervening passive cross-over - meaning that in every conceivable way in a domestic setting it’ll simply cruise along under the best of conditions. Maybe that amp is even overkill as it is, but I’ll never part with it.
