When you say that the Mac "simply doesn't have enough horsepower" is it a borderline case or not even in the ballpark?
Frogman
this reminded me of something that I feel is really important regarding the 801 but also the other matrix line as well.
We have already discussed how the speakers were designed to work with the bass alignment filter - aka an equalizer.
The BAF has two benefits and if your amp is borderline SS or Tube - the BAF can only help and this is why.
First - it makes the speaker more efficient. I have had discussions with B&W on this to confirm it. But they don't have the measurements.
Secondly and one of the reasons they become more efficient.
If you play vinyl, much of it has subsonic frequencies recorded in the grooves. The BAF has a 19 hz cutoff.
This means the amp's energy reserve is not wasted playing those sub 19 hz frequencies, making the woofers pump. leaving its power reserve for what you can hear feel above 20hz. In effect giving it more headroom. All speakers benefit from amps which have lots of headroom.
This is why its important for Wemfan or any one else to try to get the most powerful amps they can SS or Tube and not just amp/s that will work for the situation. Too many 801s are just hooked up to HT receivers because it works.
There is a rumble filter on my preamps but I choose not to use them as they are too close to the vinyl source for me. Since the speakers are designed to be used with their own spec'ed out factory filter - this is much different.
When you set up the BAF there are two rows of pins on the circuit board, one for each speaker with 10 pins locations that you set either (on or off) for each matrix speaker 800 - 805.
All 800 series matrix line utilize different pin arrangements per B&W testing.
An observation
When I got the 800's I pulled the woofers and brought them in to get checked out. One of the tests they do is placing the woofers magnet end on the table and hooking it up to a cd that plays a test signal at 20, 25, 30 hz.
This signal is stronger than anything we will ever (or should ever send the woofer) through normal use.
With the test the woofer starts oscillating up and down the cone. This shows if all parts are working properly.
So if your amp is borderline - the BAF will only help you. At first when you hook it up it will seem as though you have made the sound more lean as the 100 hz plateau is removed. This also allows for better positioning in smaller rooms.
Wemfan - are you able to identify music you have with 20-30 hz material in it. if so in your large room there may be enough space,
as ZB said to allow them to bloom without the filter.....
I can recommend a few from last night.
Count Basie - Party
Patricia Barber - Companion
Beatles - Abbey Road - side two
Dead Can Dance - Anastassis
Lorde
Sarah McLachlan - Solace, Fumblin for Ecstasy
Frogman you mentioned VTL - Poster Vegasears uses VTL's.
I know people who use various SS, and Tube. Tube including Push Pull (most common), OTL's and even one that uses a SET with his 801 in a small room. he doesn't listen to music with a lot of bass however.
So the type of music you like to listen to plays a big factor here.
TLS49 - do you recall the type of music you demoed the 801's with when people auditioned them ?
Cheers