I checked my cabinet's ohm load and found it to be different than I expected. It tested at 2.6 ohms, I used 2 different multimeters and used different speakers as a control. The cab is a mesa 8x10", the tens test pretty close to 4.2 ohms each. I tested an EVM 15L that said 8 ohms and it tested at about 5.7 ohms. I also tested a jensen 32 ohm 10" that tested at about 25.7 ohms. I am confused about acceptable ohm load limits. I am running a Sunn/Fender 300 Tube amp and I would like to run it as efficiently as possible. How should I interpret these ohm load readings? The amp has a switch that rates the output at either 8/4/2 ohms. Ideas!?

when you're measuring your speakers/cabs, you're not measuring the impedance, but rather the DC resistance. There are components to the impedance that you can't easily measure, the capacitive and inductive reactance. So when you measure the resistance, it's always a bit lower than the impedance. I can't say exact numbers, but an 8 ohm cab will measure 6.5, a 4 ohm cab 3.2, whatever. It's always low by like 15% or 20% or something along those lines, *roughly*. Nothing to worry about.

Based on what you measured, it sounds like you've got a 4 ohm cab, so that's what I'd set the amp for.

seconded, what scott wrote.

I'm wondering why the mesa 10's measured 4.2 and not less than that? I mean, what components are different there making the dc resistance close to the impedance?

Just to see, I went to my neighborhood guitar shop and measured the Ohm load of a Henry the 8x8 that claimed it was rated at 4 ohms. The meter read 3.0-3.1, so this kind of jives with the stuff Scott was saying. Not to mention, my multimeter isn't probably the most accurate way to measure DC Resistance. I also talked to my friend who works at a Mesa and Fender repair shop and he said, "Run it at 4 ohms".