07-25-11: AudiozenI think you are referring to the dynamic range spec provided at the Bel Canto website, which is indicated as 120 db for the REF1000M.
The two factor's I look at for class D is the ampere output, and the db level the amp can achieve before signal break up occurs. The Bel Canto's can be taken all the way up to 130 db's before strain occurs. That's damn impressive. Sonically, class D amps that have high DB and ampere numbers will always sound sonically superior especially on the bottom.
07-26-11: Audiozen
Correction...the db level of the Bel Canto is 120 db's, not 130 db's..my mistake
That has no direct relation to maximum sound pressure level, which of course is speaker-dependent. It apparently refers to the ratio of maximum rated output power (1000W into 4 ohms, 500W into 8 ohms) to the power level corresponding to A-weighted rms output noise (90 uV).
Those numbers calculate, btw, to 117db of dynamic range into either load impedance, not the 120db which is indicated.
In any event, maximum sound pressure level in db should be calculated based on the maximum power rating, speaker efficiency and impedance, listening distance, and speaker wavelaunch characteristic (planar, box, line source, etc.). Dynamic range has no direct relation to that; it just indicates how far below maximum spl the amp's output noise level will be.
Regards,
-- Al