Question about set amps and low sensitivity spkrs

Many tube amps do not work well with B&W's (and a lot of other speakers) because of their impedence, both nominal and min/maximum, not because of their efficiency (so much). Optimally, tube amps like to see flat impedence curves about 8 ohms or higher. Speakers with dips below 4 ohms can be a problem and speakers with big swings in the curve as well can be a problem.

Speaker efficiency is not as important except as to volume potential. Actually 18w will give you some moderate sound levels in a modest sized room BUT you might no like the sound at all.

Your new amp will probably have 4ohm out put taps. Hock up to this, don't overdrive your speakers, and you'll damage nothing. BTW, be very careful in your selection of new speakers. Many folks advertise how their speakers are tube friendly when in fact they may not be at all.

Hope it all works out for you, you've taken a difficult approach to getting a good system(to your ears) by buying a small SET amp without having specific speakers to match it with. :-( IMHO of course.

FWIW most tube amps put out the same wattage at 4 & 8 ohms. It neither doubles nor halves. 18w at 8 ohms is going to be 18w at 4 ohms.

Pubul57, Don't think so, but I've never owned or researched a MR amp. Nice stuff though.

FWIW the only thing I know of that halves power output of an amp, accross the bandwidth, is (for example) an amp which uses multiple types of power tubes and, say, is designed for max power from using 2 6550s/KT88's/KT90's per channel and putting out 80wts +/-, but the amp also allows for substitution of EL34s/6L6's. Putting in the EL34's etc will about halve the power output. Lest someone get anxious, this is not so with amps that are very conservative, such as Primaluna which doesn't seek max power from the principle tube, therefor doesn't reduce much more than a few watts when the smaller power tubes are used.

FWIW.