Using 2 x 12 cab with 120w valve head

Gwydion

So I have my crate blue voodoo 120h head with 4 x12 cab... this is one hectic big setup for most venues I play... Space obviously is also an issue on stage.....

Can I use a 2 x 12 cab with my amp head?? Will it be ok? overkill for the cab?

Thanks

needleshy

someone please correct me if i'm wrong ..... it should be fine as long as the 2 speakers have a combined power rating equal to 120w. So if they are 2x 60w speakers it would be cool......

ezietsman

needleshy wrote: someone please correct me if i'm wrong ..... it should be fine as long as the 2 speakers have a combined power rating equal to 120w. So if they are 2x 60w speakers it would be cool......

yes, and only if you're playing the amp near full volume. You can get away with less wattage if you're careful but I wouldn't recommend it. Big amp is big ?

Psean

Also make sure the impedance of the cab isequal to or greater than that of the amp. You'll need to check the impedence of each speaker, and whether they're wired in series or in parallel.

Shibbibilybob

Psean wrote: Also make sure the impedance of the cab isequal to or greater than that of the amp. You'll need to check the impedence of each speaker, and whether they're wired in series or in parallel.

NOT GREATER THAN!!!!!
You need to match your impedance! That is of the utmost importance. Power ratings or speakers are a bit more personal and you could have a variety of power ratings that would all work with the difference being in the chunk and break up of the speaker. But mismatch your impedance and you will blow your head. It's not a matter of which sound you prefer, it's a matter of sound or none.
ALWAYS ALWAYS ALWAYS make sure you plug your speaker into the correctly rated output.

Luckily, most modern amps provide either a variable impedance on the output, or a few different speaker outs for different impedances.

Psean

Shibbibilybob wrote:
Psean wrote: Also make sure the impedance of the cab isequal to or greater than that of the amp. You'll need to check the impedence of each speaker, and whether they're wired in series or in parallel.

NOT GREATER THAN!!!!!
You need to match your impedance! That is of the utmost importance. Power ratings or speakers are a bit more personal and you could have a variety of power ratings that would all work with the difference being in the chunk and break up of the speaker. But mismatch your impedance and you will blow your head. It's not a matter of which sound you prefer, it's a matter of sound or none.
ALWAYS ALWAYS ALWAYS make sure you plug your speaker into the correctly rated output.

Luckily, most modern amps provide either a variable impedance on the output, or a few different speaker outs for different impedances.

Cool. Thanks for pointing that out. I'd always thought it was like a minimum load kind of thing...
My amp has a range (8-16ohm) on the output.

Shibbibilybob

Yeah so that would normally use the 16ohm out to a single 16ohm cab or two 8 ohm cabs in series.

You would then use your 8ohm out for a single 8ohm cab, two 16ohm cabs in parallel or even 2 4ohm cabs in series.

Gwydion

So my head has 8 ohm and 16 ohm options, am I correct by assuming that if I pick up a 2 x 12 cab that is 8ohm I just make sure I connect it from my 8ohm selection on my head??

Shibbibilybob

It's as easy as that ?

MikeM

Shibbibilybob wrote: NOT GREATER THAN!!!!!
You need to match your impedance! That is of the utmost importance. Power ratings or speakers are a bit more personal and you could have a variety of power ratings that would all work with the difference being in the chunk and break up of the speaker. But mismatch your impedance and you will blow your head. It's not a matter of which sound you prefer, it's a matter of sound or none.
ALWAYS ALWAYS ALWAYS make sure you plug your speaker into the correctly rated output.

Luckily, most modern amps provide either a variable impedance on the output, or a few different speaker outs for different impedances.

I disagree. One level of mismatch either way is acceptable if the amp is designed properly.

AlanRatcliffe

MikeM wrote: I disagree. One level of mismatch either way is acceptable

Depends on who you speak to. Most will tell you lower by half is acceptable, but never higher as the unused power feeds back into the OP tranny. Impedance varies for different frequencies anyway, so there is some leeway, but the nominal rating lets you match within the range available without stressing anything unduly.

if the amp is designed properly.

if... But then again, some are purposely designed with undersized/underspecced trannys for what that does to the sound, and they will be far less tolerant of mismatches.

LooneyAtTheGate

Has anyone on Guitarforum ever blown a head, and if so what do you do? What components must you replace and how expensive is it?

Shibbibilybob

I once had to replace the main transformer in my 120watt high gain tube head. It was arcing for an unknown reason, that seemed to be related to a slight nonuniformity in shape.
It cost me about R2500 to repair.

MikeM

Run a mismatch at some time or other with all the amps I own, besides a twin, and have never had an issue.

lapdawg

MikeM wrote: Run a mismatch at some time or other with all the amps I own, besides a twin, and have never had an issue.

Now I'm curious - Is there a reason for running a mismatch?
My understanding is as per what Alan is saying - you put strain on the OT.