Tube vs Solid State

why he would have found the vertical biamp configuration to result in a less weighty deep bass compared to running the amps in bridged mode.

Bridged = less damping factor = less control = thicker bass (weighty?)

Cheers George

"less weighty"

Al and George,  I might add, may not be listening my music at loud enough volume to 'feel' low bass frequencies in vertical bi-amping. 

I normally listen to my music at 60db's. I had someone come over last weekend and we conducted some A/B comparison. His preferred listening level was right around 85db's which was bit uncomfortable for me :-)

Don't know about you guys, my room is 15'D x 30'W and 60db's is plenty loud. 

Don’t know about you guys, my room is 15’D x 30’W and 60db’s is plenty loud.

In that size room that’s a bit quiet for me, especially with the 800D’s, they are a speaker that’s likes to be driven to get the bass going, at those low levels I’d want the old fashion loudness switch on. And this may explain why you may like bridged mode because the damping factor is less and the bass may be warm'ish(sort of a loudness switch)

Cheers George

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

Al, you are spot on amp gain in bridge mode, it's 32db. I mostly listen to jazz and classical music. I think it's worth a second shot to  try vertical bi-ampimg again tomorrow and increase the volume upto 80db to compensate for -6db gain. 

George, good point. A loudness switch is what I need :-)

Thank you both for great feedback!