How about a populated board? We could maybe build our own head chassis.

Well, keep in mind that resistance is a type of impedance.

Or, just wire it like with JM's schematic, where the resistance between the hot terminal and the wiper terminal is basically R1 and the resistance between the wiper and ground terminals is R2. But, of course, the resistance across the outer terminals is more than double the 8 or 10 ohms in JM's schematic.

In my case, I put a couple of 10 ohm power resistors (rated for 5W each, I think) in series, and put that series in parallel across the outer terminals of the pot. The input jack (coming from the amp) is connected across the outer terminals of the pot as well. So with no speaker plugged into the attenuator, the amp "sees" about 11 ohms of resistance. The output jack (going to the speaker) is connected to the wiper terminal and which ever outer terminal is connected to ground. With an 8 ohm speaker plugged in and the pot turned all the way up, there will be about a 5 or 6 ohm impedance. As you turn the pot down, the impedance "seen" by the amp approaches the 11 ohm resistance seen without the speaker plugged in. And, of course, as you turn down the pot, the current through the speaker is reduced. There might be a better way of doing this, but it is an easy attenuator to make, and allows you to adjust for a trade off between attenuation and good tone. It sounds good with my ruby. Sounds like crap through another homemade amp. Haven't tried it yet with my 5W ValveKing royal 8 yet. You might do better wiring the pot as a rheostat and use it as R2 in JM's schematic.

For a very small amp, like the ruby or a small 5w tube amp, the 25 ohm pot sold at radio shack isn't too bad.

You could possibly rig something up to do the measurements yourself. You can put a sine wave through your amp and hook up an oscilloscope across the speaker terminals. Then adjust the gain until you have one watt across the speaker. You might need to put a known resistance in series with the speaker to measure the current to help determine power since the exact impedance of your speaker at that frequency isn't going to be known (I guess you should use a 1 khz frequency for your test signal).

After knowing the power put through the speaker, you can then measure the dB spl, which I unfortunately am not to sure about how to do. Has anyone here made such measurements?

I bet someone could rig up an arduino board to both generate signals at a variety of frequencies and take measurements of the current through the speaker by measuring the voltage across the sampling resistor. And maybe even read the signal level from whatever microphone you use for db spl measuerments. Maybe after measuring all this, you can compare the impedance and frequency response curves with those from known eminance (or other manufacturer's) speakers to figure out which model was rebranded for your amp.

The first thing I noticed when I first opened my Crate GFX-212 was that the transistors were mounted to the chassis.

Cool deal. Thx for sharing that.

I know this isn't related to the OP, but what did you think of the firefly? I'm kinda considering building one.

Here's an example of a ruby played through proper speakers. http://www.youtube.com/watch?v=hv-EN4qlCgc&feature=related

Hehe.

It seems like I figured out one time that using pennies as a source for zinc would cost about twice the market value for zinc. I imagine the negligible amount of copper plating wouldn't hurt anything. I think some Zamak alloys even contain a bit of copper. But it certainly would be cheaper to find scrap zinc.

I'm sure the Mod 12-70 is much better if he can afford it. If he's scavenging little speakers from stereos, he might need something cheaper. There's a Mod 12-35 that's in the lower $40 range. That's not all that much more than the Mod 8.

Sorry, JM, I might have misread your post.

Not talking about making pennies, but using pennies as a source for zinc to make zamak.

I can also use American pennies. It would not be as cheap, but they are easy to find. I'm, of course, not going to do that, though, because that would be illegal.  0:)