The speakers are approximately 7 x 7 x 12 inches. The driver is a single FE-103 4.5 inch Fostex. The finish matches the amp and preamp in every way. The standard is walnut and black as your amp was. We offer other finishes for a small adder in price.
Using the EQ built into the preamp or power amp the speaker has much better tonal balance than most of the single driver speakers I have heard. I think many of these little high efficiency speakers sound rather thin and hard to listen to. The same applies to open baffle and they need even more EQ. The EQ really fleshed things out in every case.
In order to make high efficiency speakers the driver maker has to use light materials, strong magnets and pretty much take what he gets. If he is allowed to make a driver less efficient he can generally obtain more uniform response. When he does so the efficiency is reduced over the whole frequency range.
Here's something to think about. We know that adding mass to a woofer makes it go lower in frequency but it also demands a high price in efficiency. In fact, the loss of efficiency is exactly 12 dB for every octave of extension. That's 16 times the power to get the same acoustic output one octave lower. No wonder most subs have very high powered amps. I took the opposite approach. I chose a very light polypropylene woofer with a high resonance and operate it on the down slope. It takes EQ to do this, but I end up with a very fast woofer because the mass is considerably less than doing it the other way. This is what I had to do to make the woofer fast enough to go with my electrostats.
Back to the electronics:
All 3 amplifiers and the preamp are the same size so any amp will go with the preamp. All the power amps have similar gain but there the similarity ends.
The 2.5 has cathode bias, no adjustments, plug an play.
The 5.0 has adjustable bias and one uses a meter to set it. One can also influence the sound of the amp by changing the bias.
The 12 watt mono has both bias and driver adjustments so one can really get into changing the sound with those. These trim pots make much more difference than tube rolling. I feel a lot of tube rolling differences are more the bias point of the tube and how the tube interacts with the circuit. I am always reluctant to say a certain tube sound a certain way in every amplifier. That's just too much to expect.
