Ohm question

[toejam]

My amp is a Mesa F-30 1x12 combo. The speaker is an 8 ohm Celestion Vintage 30. There's three speaker outs on the back... the one for the combo is, of course, 8 ohm, the two extras are both 4 ohm. Underneath the 4 ohm outputs, it says use with two 8-ohm speakers. I assume that would be if I'm using a 2x12 extension cab. My question is: What if I want to hook up an extension cabinet, like a 1x12 or even a 4x12, what ohm speakers should the cabinets have? I'm confused. [img]graemlins/help.gif[/img]

[charvelguy]

Re: Ohm question

what I believe it means is that it should take two 8 ohm cabs....one for/on each side of the two 'out' jacks making the resistance 4 ohms total.

It doesn't matter if your hooking up a 1x12 or a 4x12, as long as the total impedence of each cab is wired for 8 ohms to the female jack of that cab.


It would be unusual to have a 4 ohm cab per out jack, as most guitar amps do not run at 2 ohms impedence..bass amps yes, guitar amps, no... so I'm betting 8 per side.


You may have to unplug the internal speaker if running the two external as well. Best to check with Mesa on that, but that is how it sounds.

[mulder1966]

Re: Ohm question

Sounds correct [img]images/icons/smile.gif[/img]

[toejam]

Re: Ohm question

Thanks. So if I get an 8 ohm 1x12 cab and hook it up to one of the outputs, I'll be okay and won't have to disconnect the combo's internal speaker then, but I probably would have to disconnect it if I had two external cabs hooked up?

[charvelguy]

Re: Ohm question

yes, that is how it sounds.
Your output transformer should have wire taps for 8 and 4 ohms. It sounds like Mesa has split the 8 ohm tap or has a circut to switch when you plug in a jack.

So if you run one 1x12 8 ohm extension cab.. I would leave the 8 ohm internal speaker plugged in.

If you run two external 8 ohm cabs, you unplug the internal 8ohm speaker.

[toejam]

Re: Ohm question

Thank you, sir! [img]graemlins/toast.gif[/img] It's starting to make sense now. [img]images/icons/smile.gif[/img]

[Dreamland_Rebel]

Re: Ohm question

if you hook up another 8 ohm speaker cab to you combo which has an existing 8 ohm speaker, you would need to put both combo and ext. cab into the 4 ohm outs.

when using 2 cab you cut the impedence in half.

since all mesa cabs are pretty much 8 ohms, they give you one 8 and two 4's. so you either use one cab in the 8 or 2 cabs in the 4's.

pretty simple.

if you want confermation give boogie a call they will tell you the same thing.

www.mesaboogie.com

[toejam]

Re: Ohm question

Ah, I got it now. Thanks, man! [img]images/icons/smile.gif[/img]