Biamp N802:is 55W tube enough for high/mids?

Energy in music drops with increasing frequency so although you have a 4 ohm dip in the mids, your amp won't have to deliver as much power as they would at, say, 30Hz and 4 ohms. Give it a shot - I think you will have no problems at all. I biamp my speakers with tubes on top and they sound better than ever before. However, B&Ws are not the best suited for that arrangement since their lower crossover is kind of high at 350Hz. But it is still worth a try.

Arthur

As Arthur notes, you should be able to do it. OTOH, 350Hz places you smack bang in the middle of the voices range, so most of yr tenors will come out of the "bass" amp and most of yr sopranos fm the triode (likewise with cellos and violins):)

Just check that your triodes of choice sort of maintains constant power between ~3,5ohm and ~8-10ohm.

Of course, you will test this before you buy, right?

Anyway, depending on how the triode behaves under test, you can guess at the end sonic result from an amplitude point of view.

Having owned several sets of b&w's, inc. M802's, & knowing how much power they require, I'm skeptical. But then, I never tried to bi-amp them. A more complete list of your system, power amp, etc., would help.....

Two different amp signatures crossing at 350hz does indeed sound terrible. I tried it and that's how I know. N802's will play fine with 55 tube watts, PHI110 in triode but I usually run the 110 watts in ultralinear.