Turning a Marshall 4x12 into a 2x12

JulianLM

Member
Messages
44
Hi !

After a few tests it's much better to use only 2x12 instead of a 4x12, it helps to reduce the volume of a 100 Watts head (And 4x12 is too much for most common use).

So I got a Marshall JCM900 1960A and I'd like to turn it into a 2x12, Marshall 2061CX style, 2 speakers diagonally.

Do I have to close the two holes of the two speakers I'll remove ? Or is there's no impact on the sound if I leave the holes as is ?

BTW, if I unplug 2 speakers, the impedance will be 8 Ohms and not 4 anymore as it's mentioned on the cab, right ?

Thanks :)
 

Hefalump

Member
Messages
10,862
I used to run a 1960a cab I have split (two amps feeding it). Sounded darn good with just the two speakers running....took off a bit of treble and was more bassy.
 

JulianLM

Member
Messages
44
Yep that's what I feel like too !
So you have 8 or 16 Ohms available, right ? Not 4 or 8 in stereo mode anymore.

But I don't want to cut the cab...
Thanks for your reply :)
 
Messages
7,833
Marshall used to make one just like that, called the 1961 (not to confuse w. the Blues Breaker) and some players tried to do a 1961 mod to their 1960s for a similar effect.
20130724041436-8db02fef-me.jpg

I'd certainly try to block the holes or keep some speaker drivers in there as passive radiators. Otherwise you'll achieve cancellation of sound, which particularly makes the lows suffer.
 

Hefalump

Member
Messages
10,862
That's something I'm aiming for. Which speakers did you keep? Upper ones or lower ones?

I just used the switch on the back of the cab to run in stereo setting which takes the cab and splits it down the center. I did not remove any speakers.
 

JulianLM

Member
Messages
44
Ok thanks !
Yes I'll do as we see on the picture.

Why not getting a 212 ? Because I don't have money ! That's why ! Lol
I got this 412 since 2005 or something.

And as I saw this 1961, this gave me the idea to tweak the 412 into a 212 for home recording/playing but I don't want to destroy anything so I'll be able to put 4 speakers again one day.

One more time, why about the Ohms ?
With 2 speakers removed it's 8 regular or 16 Ohms stereo instead of the 4 regular and 8 Ohms stereo, right ??
Tried to run the amp at 8 Ohms with the cab for a few mins but I got to be sure for not to blow anything :/

Thanks a lot for the pic !!
 
Last edited:

garytube

Member
Messages
205
I used to do this with a 4x12 and used two speakers in both top positions, leave the bottom ones open with no speakers, sort of a detuned cabinet type thing. It sounded fine to me, and made the cabinet a bit lighter.
 

michael.e

Member
Messages
20,762
I have done this with a number of cabs. I kept the speakers diagonal. I tried this cheap "detuned" method and did not like it for live work. My 4-12 cab now is split in to pairs of 8ohm speakers wired to 16ohms.
 




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