High vs. Low Efficiency Speakers

Duke above did a great job of explaining the factors of a speaker of lower effiency vs. one with a higher one. One other factor to consider is the nature of the load, i.e. the impedance vs. frequency curve. If you have a relatively high voltage sensitivity but a difficult load (one with low impedance and/or high phase angles), an amplifier with a high output impedance could have as much trouble driving that speaker as it could driving a speaker with a lower voltage sensitivity and a higher impedance load. Also, in some cases, your amp will drive the load to satisfying sound levels but its interaction with the load can significantly alter the tonal balance of the speaker.

With your preference for classical music, I would recommend going the higher effeciency route and since you don't listen that loud, try a SET amp out sometime. Good luck.

Agree with Duke's excellent assessment but I might add that one might not need super efficient, "big box" speakers in this scenario. A speaker with efficiency in the 90 to 95 range would work quite well with low powered tube amps and have good, appropriate bass. A couple speakers that come to mind are Coincident, Reference 3a, Meadowlark, Merlin and Living Voice. All are average size speakers.

To quote Ralph Karsten of Atma-Sphere: "...if you want a tube amp, even if you don't want an OTL, you should avoid four ohm speakers. " cf. "Debunking Common Power Amplifier Myths"

I do not think it is possible to generalize. I have heard a few high efficiency speakers: Lowther, Tannoy, Avantgarde, and Zu. And I have heard a few low efficiency speakers as well.

In general, low efficiency speakers have a brutal kind of sound. These are typically very linear sounding, with ample bass. The sound from these speakers are typically very impressive. But as we all know, impressive does not necessarily mean they are musical.

The high efficiency speakers I have heard, without exception, suffered from problems. The Tannoys have a lazy coloration that kills the rhythm of music. The Zu's sound distant and uninvolving. The Avantgardes have horn coloration. The Lowthers are beautiful, but lack treble and bass extension. (Yes, I know this is a gross generalization but it is based on the systems I have heard).

Of all the high efficiency speakers I have heard, the Lowthers impressed me the most. But that is my particular musical taste (classical). YMMV.