What do I do if...

[fuzzhead]

My cab is a 16 ohm cab and my mark IV only goes as hi as 8 ohm?

 

[Whoopysnorp]

Rewire the cab for 4 ohms. That's what I did a couple nights ago.

 

[kiff]

how many speakers and what are they rated at? If possible I would suggest wiring for 8 ohms, then you can either run it by itself (using the 8 ohm out) and if you get another (8 ohm) cab you can run them both using both of the 4 ohm outs

 

[Whoopysnorp]

I don't think it's electrically possible to take a speaker set wired for 16 ohms and rewire it for 8...at least I can't think of a combination where that would work (except if you had four 4 ohm speakers wired in series and you just removed two of them from the circuit).

 

[fuzzhead]

It is a splawn 2x12 cab.
I don't know yet what impedance the speakers are.

 

[Whoopysnorp]

I'm 99 percent sure they'll be 8 ohm speakers and they're wired in series, because otherwise they'd have to be 32 ohm speakers, and that's just practically unheard of for guitar speakers. If you rewire them for parallel you'll get 4 ohms. Here's a link to a number of wiring schemes for two speakers. I'm planning on putting a switch in my 2x12 so I can switch between series and parallel and thus between 16 and 4 ohms.

 

[kiff]

I don't think it's electrically possible to take a speaker set wired for 16 ohms and rewire it for 8...at least I can't think of a combination where that would work (except if you had four 4 ohm speakers wired in series and you just removed two of them from the circuit).

It is a splawn 2x12 cab.
I don't know yet what impedance the speakers are.

yea, I'd guess they must be 2 8ohm speakers in series, so you might be stuck only being able to get 4 ohms from it by rewiring in parallel. Of course you could get new (16ohm) speakers, but...

 

[fuzzhead]

I actually have no problem getting a couple of new speakers...
I like the cab a lot, so I would rather replace the speakers than get a whole new cab.
So,
Series and Parallel... telling the difference.

If I get two 16 ohm speakers can you guys guide me on the wiring?
Also,
There are eminence speakers in the cabinet currently,
but I am thinking of going with celestion.
I'm sure everyone has played the v30's, but what about the G12H?
Thanks for all the help!

 

[tony777]

You can run the amp with 16 ohms speakers without harming the amp, you just have to drive set the output level a bit higher than with 8 ohms, and maybe you wouldn't notice at all.

But if you wish to wire two 16 ohms to 8 ohms, they must be connected in parallell, and you'll have to connect the + on the first speaker to + on the second, and the minus to the minus, and then the plus to tip, and minus to ring at the jack input.
It is very easy to do.

 

[fuzzhead]

Cool,
I just didn't want to damage the amp.

 

[sixtonoize]

You don't have to worry about damaging the amp. Mesas are VERY tolerant of impedance mismatches.
They even encourage mismatching in most of their manuals.

 

[6L6C]

This is a 2x12 right? That is a 16 ohm cabinet.
Which is going to mean 2x 8 ohm speakers.
Two eight ohm speakers can’t be wired for eight ohm’s. But if you wire them in parallel it will yield you a 4 ohm cabinet (as opposed the 16 you currently have in series) and just use the 4 ohm connection on the Mark IV. But when doing this DON’T plug in any other cabinets.

 

[camsna]

Dude. You don't have to do anything.

Plug the 16-ohm cab in to the 8-ohm output. It won't harm the amp at all and you might actually dig what it does tonally. It's barely noticeable, but give it a try and let us know what you think!

 

[mr_fender]

Agreed. Driving a 16 ohm cab with the 8 ohm out is just fine. Mismatching to a higher load is safe. NEVER mismatch to a lower load though, unless you like buying output transformers.

Twice the impedance will give you half the current and therefor half the wattage (in theory :wink: ). The result will be a 3db drop in output volume. 3db is barely noticable to most people. The tone is usually a little bit darker sounding too. Again hardly noticable to most. MarkIV's are plenty loud, so you should have plenty of power to just push the output level up a bit.

If you're hell bent on keeping the amp as efficient as possible, rewire the speakers in your cab to parallel as suggested above. That will make your cab 4 ohms overall and you can plug it into the 4 ohm output.

 

[fuzzhead]

I actually had been playing the amp for a few days with it plugged into the 8 ohm spot. I just realized that it wasn't an 8 ohm cab and freaked out :shock:
Glad to hear it didn't hurt the amp!
Thanks for the input... If I do rewire the cab for 4 ohms,
what would that mean tonally. Is it driving the amp harder?
Thanks again!

 

[Whoopysnorp]

It would mean you wouldn't be getting the very subtle darkening and volume loss that you get with the impedance mismatch. Changing your settings would have a far greater tonal effect.