Thanks for the info and the link. I have problems finding papers on the AES web site.
Too bad this is not a Journal paper as a local library has them to about 1992 when they cut back due to budget. I don't have that paper
The left and right direction of the block is phase angle with the center being 0 degrees or totally resistive. Hence, the block that is bad, the center of it is closer to the good amp.
The front to back direction is the rail voltage in relationship to 8 Ohms being at the back and 1 ohms the very front.
The block that represents the Behringer A500 is similar to the good amp block, no rail voltage sag due to phase shifts.
By the way, the power cube measurement for it was a little better than for a Bryston 875 at $5k.
Do you know how accurate the meters are?
Unfortunately no, but it seems pretty good from rough, brief tests at around 1 watts and spl readings.
Certainly what you've said is in agreement with what Martin Colloms wrote, that on good programme material, the demands on the amplifier will be fairly low most of the time.
Yes. So, if it was around 1 watt, let's assume as in his case it was well below that, a 20dB peak would be 100 watts and that is before the dynamic headroom power is used.
Now, in his case, much was around .1 watts, that is why it was rarely peaking anywhere near 20 watts on the center ch. That would give a 30 dB headroom in his case, to 100 watts. But, some speakers are very demanding, no question. Amps are not designed around the most demanding speakers though as they are in the minority.
It's just a question of being able to produce the high currents necessary for reproducing the loud musical transients without clipping. If you're routing the bass to the subwoofer, then this must help to reduce the possibility of clipping, since it's usually the bass region that clips first. Of course using the subwoofer in this way is like bi-amping.
Yes, the bass does use a lot of power, no question. One reason is the ears insensitivity to it and the perception of loudness, Fletcher-Munson curve comes to mind.
The main speaker is on large though as it has a 12" driver beside the sub. The LFE goes to the sub to 80Hz. Other in channel lows do go to the speakers, however. Even with that, the observed power was what is above.
No question that not all speakers created equal and some are very demanding on amps. That is why speakers need to be picked first, not after the amp is home and a speaker must be found for it.
One more try

THD is usually measured at RMS power ratings, 1 watts or full power. So, you can get an idea of the 4 Ohm THD when it is given, usually not much worse than the 8 Ohms. Same goes with the dynamic power although that rating may be at a bit higher THD level, not sure.