efficiency- hope i spelt that wright.

Magnus, a speaker should always be viewed in relation to what amplifier it would be used with.

If you have a low output (low wattage) amplifier, especially the vacuum tubed variety, you would want to use a fairly efficient speaker with high(ish) impedance rating and benign impedance curve.

If you have a huge, high watt solid state amplifier, you would normally want a less efficient speaker with a lower impedance rating. Very efficient speakers on big amps sometimes result in a audible hiss. (Note, I said sometimes, not always). Low efficiency speakers go a long way to hide amplifier and line noise.

You’ll find that many very efficient speaker are expensive, and it normally works out cheaper to purchase a bigger amp with less costly less efficient speakers.

Low output amps are also not always cheaper. Many single digit output tube amps can retail for many tens of thousands of dollars. Price of the amp is determined by a number of factors, not always simply on output.

Regards
Paul

Have 94db Horn with 7" coil drivers.I tried some SET and it will work but again as mentioned above you often have to discern what they will play with and what they will require to open up and give dynamics's.Fro mine I would say that only a 22 wpc 845 tube SET has enough power or better a 40 watt push pull.And as I have noticed many speakers require more than specs say.B&W's I sold (say the 803 at 8ohm nominal and 90db sens you would see that and think it's an easy drive.But try that speaker with a 80-100 SS or a 45 watt glass amp.It had such a nasty impedance swing on transients a t volume that would be cheating youself with less than 200 watts SS 150 glass better a 300 watt SS and 200 tube amp though they would work with 100 tubes just not open up.And they were speaker that did not get much from tubes as many others.As always few specs can be looked a without taking ion many others to judge what there requirements will be.
Chazz

Some of the issues regarding amplifier vs speaker selection are discussed here:

http://www.atma-sphere.com/papers/paradigm_paper2.html

My own feeling is that if the efficiency of the speaker does not interfere with the revealing nature of the speaker, does not interfere with bandwidth, then the efficiency is valuable! My own speakers are 97db 1 watt/1 meter, compared to a speaker of 87 db, the result is that I can run an amplifier of 1/10th the power and get the same sound pressure. Fortunately, one thing high efficiency speakers do really well is dynamics- no worries there.