Stereomour - Full Range Driver Efficiency

[drewh1]

OK, I am hoping Paul will help me with this one.

Wanting to build Full Range Metronomes with Fostex 208esigma to match up with my Stereomour (when is that thing going to ship anyway?). The speaker is 8 ohm, 97 db efficiency. The box design calls for the addition of a 4 ohm resistor in Series with the 208e. So this would make the speaker impedence 12 ohms? how would this change the efficiency and would this be a match for the Stereomour (higher impedence should be better right?).

[Doc B.]

We're waiting for some parts to arrive before we ship the next run of Stereomours. Some should start shipping next week.

[Paul Joppa]

The box design is probably for solid-state amps with (essentially) zero output impedance. SETs with no feedback, such as the Stereomour, will have an output impedance that is close enough to 4 ohms (I estimate 3.26 ohms for Stereomour 2A3,  5.42 for Stereomour 45). So I would leave out the resistor and enjoy the sound.

At a later time, you could get a 5-ohm or 10-ohm wirewound pot, wire it as a variable resistor in series, and see what works best in your system. If you need a few more ohms, a small modification to the Stereomour can accomplish that goal without wasting power in a series resistor.

[drewh1]

Cool, thanks Paul!