Bring on the criticism...

I agree with the several previous descriptions of the adverse effects you are likely to encounter. More specifically, a major effect is likely to be some degree of Comb Filtering. That occurs due to radiation of the same frequencies from different drivers in different locations, with those drivers having differing path lengths to your ears, resulting in differing arrival times.

I believe that the subjective result of that is a general "cloudiness" and loss of clarity. Of course, it is likely to be most perceivable on high quality material.

Regards,
-- Al

I did this when I blew the tweeters in my JBL L88's in the '70's. Removed the tweeters and sent them to JBL for repair/replacement (which they did with no charge, even though I was not the original owner of the speakers. Wow!) Anyway, I had a month or two with no tweeters. So since my Pioneer receiver had two sets of speaker outs, I connected a pair of no-name speakers from my first department store brand stereo, and placed them on top of the big JBL's. Problem solved.

If you can afford to do that, why can't you biamp?

Can't bi-amp Maxx's

you could pay a lot less for a PA system that could do that

But it wouldn't be a Wilson PA....lol

my only question is with the volumn set in one position does the sound level from speaker set A equal the sound level of speaker set B?

Both speakers are coming straight off the FPB450's so they are being fed the same power.

Correct they are being fed the same power but are they playing at equal sound pressure levels or is one pair louder than the other;that's what I was questioning.

It doesn't matter if the sensivity of the two are different. The effect is the same a wall of sound. I did this to get as much sound as I could. Then I started to like soundstage and imaging. Now I use 1 pair at a time and my tube amps wouldn't exactly like the drop in resistance.
Although I still have some SS amps and Klipsch LaScalas which I have once or twice connected in parallel to vintage JBL C36 and C38s (Yes both using D-130s, 131s with 075 tweeters)They are exquisitely sensative and seem to compete well with the Klipsch. I do it just for sheer volume try playing BBBAD Bad To The Bone like that when you feel raucous.I am rally getting too old for that I must admit.