Hi Mark,
Sorry, busy with the Axiom newsletter.
It comes down to a matter of bass extension and real output (the EP350 does not use a DSP). When there is genuine low-frequency information on the DVD soundtrack, other subs that don't use a DSP often poop out in the upper 20-Hz region, despite the claims. The roll-off in extension and output is relatively steep, and you can hear that in side-by-side comparisons.
The EP500's DSP "linearizes" its low-frequency output, so that when there is content at 20 Hz, the impact can be dramatic because there is no significant roll-off in the EP500's output.
By the way, the soundtrack mix and low-frequency content on the re-make of "Flight of the Phoenix" is spectacular. The low-frequency content during the C-119's flight through the desert sandstorm (and subsequent crash) is wonderfully realistic; terrifying in fact. While I live in a ground-floor apartment (nothing except the basement beneath my unit), I was frankly worried that the low-frequency content would offend others in my building. That DVD is highly recommended (the movie is decent). It's filmed in the Gobi desert, and the original soundtrack uses these low-frequency African sounds.
To answer Bridgeman, the DSP code for the EP500 is programmed to prevent the digital amp from supplying more power once the DSP senses that distortion limits/and/or voice-coil excursion would be exceeded if the amp did supply more power. It's sort of a very sophisticated limiter.
Regards,
