That’s an interesting point, Lalit. The sensitivity of our ears to deep bass frequencies, relative to their sensitivity to higher frequencies, will of course be less at relatively low volume levels than at higher volume levels, per the
Fletcher-Munson effect.
Which leads me to wonder about the gains your amps provide when used in bridged mode vs. when used in a vertical biamp configuration. The gain of the amp is spec’d at 26 db, a typical number for a power amp, which I presume applies to the stereo mode that would be used when biamping. But I would suspect that their gain in bridged mode, which does not appear to be specified, may very well be (and probably is) 6 db higher. And if so, unless you took special measures to accurately compensate for the reduced gain when you tried vertical biamping the result might have been that you were listening at a somewhat lower volume in that mode, which might account for your perception of less weighty deep bass.
Don’t know about you guys, my room is 15’D x 30’W and 60db’s is plenty loud.
Although it’s not particularly relevant, I’ll mention that my room is 12W x 22D, opening to another room in the rear. My listening is mostly to classical music, and in many cases to recordings having very wide dynamic range. Average SPLs at my 11 or 12 foot listening distance are typically in the mid-70s or thereabouts, but I have at least a few orchestral recordings that were engineered with minimal or no compression, and produce SPLs that can vary between around 50 db and brief peaks of 105 db on the same recording!
Best regards,
-- Al