Mesa 4x12 OS - ohm reading


Active member
My friend bough this old Mesa cab, probably have 20 years. It look in good shape and sound good, but when i was cleaning and opening it, i measured the resistance. I read something like 30-32 ohm, with the cable plugged in the 8 ohm port. Is this normal? I checked the soldering joints, and all the speakers seem to work fine.
My cabs don't have the 4+4 and 8 ports, so is a different wiring... first time to see a so big difference.


Well-known member
Seems like someone goofed the wiring and put everything in series (four 8 ohms in series)

You can use a meter to get an idea of what the cabinet is wired for but it’s not for exact measurements since it’s measuring resistance at DC and not impedance for AC at some frequency.

I’d still check the wiring, the soldering doesn’t matter if it’s wired wrong.


Active member
I just bought an old mesa cabinet and had the volume cutting in and out. I had to clean the jacks. And the main jack is kind of a strange one too. Has a piece of plastic on the tip that I had to “adjust” back into place. I’ll keep an ear on it and will order a new one if needed.

So make sure to really clean that jack!!


Active member
Tonight i will reach my friend, clean the jack and measure the resistance again. Anyway the cab was sounding fine, very similar to my Marshall with V30.