High impedance Speakers

Classic Audio Reproductions makes two 16 ohm speakers, the T5 and the T1, which are both moderately high efficiency too (95 and 97db respectively).

I have advocated high impedance speakers for a long time, not just for my own activities, but for the fact that any tube amplifier with a high impedance tap on the output transformer will perform noticably better with a high impedance speaker (in this case 16 or 32 ohms) then will that same amplifier on a lower impedance speaker, all other things being equal.

IOW, if you are investing in a tube amplifier, your investment dollar is best served by a speaker with higher impedance, all other things being equal. If this means 8 ohms instead of 4 that's fine but 16 is better still, if the amplifier has the capability for it.

The difference in low frequency bandwith from the higher impedance taps to the lower impedance taps on an output transformer is clearly audible and measureable. Also noticable is the increase in transparency (read: decrease in distortion). It is win-win for everyone but the transistors.

A speaker that is easy to drive (more efficient) requires less of the amplifier but also of *the preamp* as the volume does not run as high. As long as hysteresis loss does not play a role (as in a large transformer coupled tube amp) the distortion will be lower- again improving transparency.

The lesson is that if you are investing in a tube amplifier, the investment is best served by a speaker that is 8 ohms or more and high efficiency. In the old days 16 ohms was common and there were even 32 ohm speakers. Since the advent of transistors, 4 ohms has replaced 16 ohms for being 'common' but to the detriment of tubes.

Using the 4 ohm tap on a higher impedance speaker will yield more 'current' but neither the transformer nor the tubes will be properly loaded. The transformer can ring (adding distortion) so it should be loaded properly. If the 4 ohm tap is used on a 16 ohm speaker, a set of tubes with a 3K load on them will suddenly see 6K. They will not make as much power and there may be other anomalies as well.