Using only 2 speakers in a 4x12 cab - Jemsite
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post #1 of 8 (permalink) Old 09-12-2009, 03:15 AM Thread Starter
 
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Using only 2 speakers in a 4x12 cab

I'd like to put 2 greenbacks and 2 V30's in 1 cab in an X pattern, but wired so, that I can use only the greenbacks or the V30's if I wish, by mounting each 2x12 setup to a separate jack at the back of the cab. If I wan to use all 4 of them, I's just use 2 outputs on my amp. If I only want to hear V30's I just unplug the greenbacks (taking correct Ohm's into account of course). That way I could also connect 2 heads to 1 cab.

Now what I once heard from a amp/cab builder: if you only use 2 speakers in a 4x12 setup, so the other 2 speakers are passive, the 2 passive ones would 'absorb' some compression/air pressure that the other speakers generate in the cab. This would result in a misrepresented audio effect.

When I asked him what the effect would be in an open cab (I supposed none as there is no compression effect....) I didn't get an answer.

I'd prefer to have a closed back of course. Any thoughts on this ?

Thanks

Last edited by Silverburst; 09-12-2009 at 04:27 AM.
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post #2 of 8 (permalink) Old 09-12-2009, 07:47 AM
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Re: Using only 2 speakers in a 4x12 cab

The way I understand your question - you want to basically have 2 cabs in one.
You'll need two input jacks. One wired to each pair. Check your speakers for ohms -either 8 or 16 and check it against your amp outputs.
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post #3 of 8 (permalink) Old 09-12-2009, 02:02 PM Thread Starter
 
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Re: Using only 2 speakers in a 4x12 cab

jep that's it indeed.

Realizing this won't be a problem. But in case I would only use 1 channel of the cab (2x12 of the 4x12), how will the other 2x12 react ? They might absorb/counter frequencies in a closed cab.
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post #4 of 8 (permalink) Old 09-12-2009, 02:33 PM Thread Starter
 
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Re: Using only 2 speakers in a 4x12 cab

Vertical mounting and partitioning with plywood might be the answer !?
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post #5 of 8 (permalink) Old 09-12-2009, 09:47 PM
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Re: Using only 2 speakers in a 4x12 cab

I think Mesa offered a 4x12 with a partition. Not sure how it performed....
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post #6 of 8 (permalink) Old 09-13-2009, 05:47 AM Thread Starter
 
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Re: Using only 2 speakers in a 4x12 cab

yes indeed they did/do:
http://mesaboogie.com/Product_Info/G...x12SDsl-LG.htm

I guess the roadking line should be quite decent

Another idea someone at Carvin forum came with, sounds great imo, especially the "slick version":
Cut your partition to shape and install with 3 angle brackets where the
partition and front baffle meet with 1/2" to screws. Also one to the
top and bottom back corners. Careful not to drill or screw through to the outside of the cab. These will be temporary so a #8 panhead screw
should work fine.

Then run through a series of sound tests ignoring any buzz from the
board. I you like what you hear then remove the partition and re-install
with Titebond glue using the angle brackets to hold in place overnight.
Remove the brackets in the morning and rock-on.

If you find your cutting isn't precise (i.e. gaps at the joints) use Liquid
Nails instead of the Titebond or caulk the joints after the glue has dried.

If you want to be slick, cut the partition, position in cab and mark both
sides. Install 3/4" x 3/4" strips along both marks with glue. Attach felt
allong all edges of the partition. Slide partition in or out depending on your preference.
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post #7 of 8 (permalink) Old 09-14-2009, 03:49 AM
 
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Re: Using only 2 speakers in a 4x12 cab

I'm pretty sure you could do it with one jack and a switch, but you'd need to change the output from your head to match the impedance before changing the switch.
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post #8 of 8 (permalink) Old 09-14-2009, 03:57 AM Thread Starter
 
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Re: Using only 2 speakers in a 4x12 cab

the electronics side is not the problem, eazy peazy, it's the accoustics that are the quesion.
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