Originally Posted by coolrda
I originally was going with Parasound A21's, but, instead opted for used Parasound 1500A which I picked up for 400+ a piece. I have three bridged to the fronts. While running the amps in stereo sounded very good, bridged they are fantastic. There's a effortless dynamic grace to the sound with 600+ watts. The slam in my small room nullifys the sub with music. Maybe it's from monoblocking the fronts but the full power of the performance is to scale. Though I plan to someday replace my amps with a step I'm in no hurry.
I suspect that one reason you may be hearing an improvement using one amp per speaker rather than one amp driving a stereo pair, is simply that the amp box is working less hard--less current being pulled from the power supply. Not to mention the monoblock aspect for unquestioned isolation across channels.
But let me also offer an additional perspective wrt bridging vs higher power. Many times we use a modest power amp, then switch over to its otherwise identical bigger brother with, say, double the output capability, and feel that there's a benefit in "authority" and "ease" due to the extra current output capability--even when playing at the same loudness as before. Having more output devices stacked in parallel allows not only this increased power, but a lower output impedance, hence higher damping factor. The bigger amp is working less hard than the smaller one.
So what do we have when we bridge two amp channels? Higher voltage swing, so more power capability on tap. What about output impedance and damping factor? Impedance is doubled, and that means damping factor is cut in half. Not a desirable thing.
How about each amp's effort? Well, the Aerial 7B impedance is rated at 6 ohm nominal, 4 ohm minimum. That means your bridged amp is seeing 3 ohms with dips to 2 ohms. Those amps are all working much harder than before, not less.
What does Parasound say
about bridging the 1500A?
>>Q. Will these amps handle a four ohm speaker while the two channels are bridged to MONO?
A. No. Remember amps bridged to mono will "see" half the impedance the speaker is actually presenting. Sustained 2 Ohm loads are not advisable with any Parasound amplifier.<<
Unless there is insufficient voltage swing in the single amp stage (which seems unlikely with >200w available), you'd probably be better off running just one of the channels in each of those three 1500A amps, and letting the other sit idle.
Just food for thought.