Running ONE Speaker in a 4x12

[Just Mike]

I wonder if this is a reasonable way to tame the volume of a 50w JCM-800 head? I haven't had good luck with attenuators and it seems that a G12-65 could take 50 watts. And leaving the other 3 speakers in the cab would allow them to act as passive radiators, still giving the Oomph of a 4x12.
What do you think? Would it be any less loud than all 4 speakers?

[908ssp]

It depends. If the amp is turned all the way up then one speaker will be a little less loud than four. If the amp is on one then one speaker will be very nearly as loud as four.

[Just Mike]

Hmmm...not doubting you, but I don't understand the logic in this.

[vanhalen5150]

With one speaker pushing air the other 3 will actually retract from the quick differential in air pressure. It will still put out 50 watts if dimed. It will still be as loud with the one speaker taking the load. With 4 running you just spread out the load but push more air while doing so. The 4 speakers if wired correctly all push air at the same time in the same direction. Wired out of phase as some guys do with an open back cabs also works as well. Push/Pull.
Ummm... I'd get a master volume installed if the attenuator isnt doing it for you.

[awangotango]

Mike, I agree, the above logic made no sense to me either. In short, I have done what you are thinking and it works. Attenuators and masters smell, all of them. period. But the problem is a single 65w will not sound great with a 50w amp and would likely pop. So, just wire a resistor in parallel with the speaker to take half the amps power and you will be in better shape. the 65 will sound better not being pushed to it's max. Better yet, do what I do and get a weber speaker motor and use it instead of the resistor, as the resistor does affect the tone a bit. The weber device is $50 or so. So cranked (lets assume a 50w is putting 80w), the 65 will now see 40w. Still quite a bit, but it will work and your volume will be reduced greatly from a 4x12. You may want to cover the other 3 holes depending on what tone you are going for.

btw. I use the setup of 2 greenbacks and the weber speaker motor in a 4x12 using a 50w jtm. (i.e. 50w tube rectified) probably putting out 60w cranked or so......Sounds (and more importantly, feels) awesome and reasonable volume

https://amptechtools.powweb.com/truload.htm" onclick="window.open(this.href);return false;

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Also, I wouldn't dwell on theories of whether one speaker vs 4 is the same volume. My experience says they are not, especially once you wire in a dummy load in parallel, the diff is night and day.

[Just Mike]

Thanks!