SET amps and speaker sensitivity.

Of course, you must also take into consideration listening room volume, dynamic range of the music you like, impedence curve of speaker and ability of amp to deliver current to that load. For example, I can get ear splitting volume from my 1w Berning Micro-zotl in my small study (70 sq ft; 500 cu. ft.) with 93 dB speakers, but that is not be the case in my living room (300 sq. ft, 2500 cu.ft. with opening into large hallway).

Ok, thanks guys. So the higher the the dB rating on a speaker, the more sensative it is? 93dB is more sensative than 90 dB and so on?

peter

That's right Peter. And dB is a logarithmic scale, so a 10 dB increase is twice as loud! Also FYI, 3 dB is perceptible as an increase in loudness (less than that is often perceived as better but not necessarily louder). So you need to double the power output of an amp to get a significant increase in volume. FYI, sensitivity is generally in units of dB/1 watt/1 meter; 1 watt (or 2.8 volts) of output, producing X dB of sound pressure measured at 1 m from the speaker.

You also have to consider the actual impedence of the speaker. Assuming a benign impedence, then 60 tube push pull watts for a 95db sensitive speaker. 30 watts for a 98db push pull amp and 15 watt SET amp for a 101db speaker. If I had a pair of Lamm ML2 I would be looking at a speaker of at least 100db sensitivity.

If I told you that I could carve a turkey with my $30k pocket knife I would not be lying. Just as SET amp maker will say that their 18 watt SET can drive a 95db speaker. Sure it might play loud, but the question is would it sound better with more power?

In SET amps as with many others, all watts are not created equal. Other aspects than simple output figures determine abilty to drive real speakers. In particular, the size and quality of output transformers is a factor. Now they are heavy and expensive, so in simplistic terms, the more you pay for an amp, the better it will drive speakers for a given output.
AS Ultrakaz says speaker impedence is very important for SET's, the speaker may be quoted at 8ohm impedence, but have nasty dips to 2ohms in the frequency range. A SET won't respond well to that.
The answer, try your speaker and SET together preferably in your own rooml, see how they match.