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.

Hi Michael,
One reason B&W speakers might not work well with SET tubes is not necessary the efficiency, rather that the impedance swings on B&W speakers in general are wide, a 8 ohm nominal speakers can be down to 4.6 ohms. And most SET do not like wide impedance swings.
I was using Cary 300SE signature (15W SET) driving B&W CDM1SE for a long time, extremely happy with the result, now granted, my listening room is small (11X14). I recently changed the speakers to ProAc Reference 8; love the ProAc mid-ranges.
So, all said and done, I think it really dependent on what type of music you generally listen to, and how big a listening area you have.
Good luck!
Roy

I agree with both Mr N and mr T: You won't hurt the SET at all listening to your B&W's. You may even be surprised by the levels it can achieve(though I wouldn't get too ambitious). Just don't try to match the SPLs the Arcam delivered. It'll start to sound bad before you get that far anyway.

Thanks for all the informative, helpful responses, very much appreciated. Well, the amp has both 4 and 8 ohm taps...the speakers are rated at 8 ohm, so I would still use the 4? Or should I sue the 8 ohm amp taps? It's funny everyone tells me I'm going about this the wrong way, by buying the amp first! I just figured I could choose the amp I liked and try to match speakers to it, but this seems to be a beginners mistake! Thanks again!

No real mistake was made. You wanted, and found an SET amp. You already knew you'd need more efficient speakers to go with it. You'll be able to listen to what you have until you get the new speakers. As long as you are building your system based on accurate information, you'll achieve your goal, regardless of the purchasing order.