The 2268 used in the SRX 728 seems to get rid of heat quite well, but from the sine wave testing Phil did at high levels it is obviously not immune from power compression. It is only rated for 800 watts continuous, so it would be unwise to test it for much time with continous levels above that.
Dynamic music would probably benefit from 1600 watt peak potential, as long as that power was at or above Fb (the box tuning, 40-41 Hz for the SRX 728).
That said, Phil’s tests show the speaker is producing about 18% distortion at 50 Hz with 900 watts, so more power may result in more distortion and little increase in level, depending on the frequency of the peak.
The JBL distortion chart shows it hits 10% distortion (and probably Xmax) at 33 Hz with only about 100 watts,
40 Hz is the low E on a bass guitar, the low B is 31 Hz.
Hit the box with 1600 watt peaks much below Fb and you will get to hear the buzz saw tones you don’t like. You might also tear the suspension up.
If you look at the charts I posted, you will notice that excursion is at minimum at Fb, below Fb output drops rapidly, and excursion and distortion also increase rapidly.
Excursion also increases above Fb to a maximum about 1/2 octave above Fb, then reduces at higher frequencies.
Both the cabinets I tested and the SRX 728 are too small to have flat response down to Fb. Larger boxes would allow the speaker to put out more bottom end at lower frequencies, but above Fb the speaker would hit excursion limits before it ran out of power.
Most box designers for the general public design boxes a bit small so people burn, rather than tear the speakers up.
“Advanced Speaker Systems” by Ray Alden (available at Radio Shack) is a good book explaining ported and sealed speaker cabinet designs.
Web research into Thiele and Small and D.B. Keele Jr. will get you most of the pertinent information regarding ported cabinet design.
Art Welter