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Converting a closed-back Marshall 4x12 to open-back

Posted: Sun Dec 22, 2013 7:15 pm
by npfrs
I snagged a JCM 800 4x12 a few months ago. It's loaded with 70's which, although everybody seems to hate, sound pretty good (being well broken in likely helps) but I never intended to keep it stock. Since I got such a good deal on it I was planning on converting it to an open-back cab with 2 blues and 2 golds and also wiring it for mono/stereo.

Has anybody converted a closed-back Marshall 4x12 to an open-back? I've found a few different ideas online...

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I also thought this was interesting...

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Re: Converting a closed-back Marshall 4x12 to open-back

Posted: Wed Dec 25, 2013 12:51 pm
by whiskey_face
ive never done it but with those greenbacks :love:

edit: I would build a totally separate back for it, instead of hacking up a marshall one.

36 x 36 sheet of void free ply
+ saw
+ router (the circular cutouts are waaaaay sexy)
+ tolex
+ an afternoon


bam easy

Re: Converting a closed-back Marshall 4x12 to open-back

Posted: Wed Dec 25, 2013 7:16 pm
by benjuro
whiskey_face wrote:
I would build a totally separate back for it, instead of hacking up a marshall one.

Re: Converting a closed-back Marshall 4x12 to open-back

Posted: Wed Dec 25, 2013 7:23 pm
by npfrs
benjuro wrote:
whiskey_face wrote:
I would build a totally separate back for it, instead of hacking up a marshall one.
Yes, definitely, but I'm wondering what back to make? Seems like Marshall themselves used to do 2 vertical side panels, and I've seen photos of EJ using a similar one. However there are some other great options out there...

Re: Converting a closed-back Marshall 4x12 to open-back

Posted: Wed Dec 25, 2013 7:25 pm
by sonidero
Just route out a huge I, L, and F...

Re: Converting a closed-back Marshall 4x12 to open-back

Posted: Wed Dec 25, 2013 7:29 pm
by npfrs
sonidero wrote:Just route out a huge I, L, and F...
:lol: :thumb:

Re: Converting a closed-back Marshall 4x12 to open-back

Posted: Thu Dec 26, 2013 12:11 am
by Decibill
I agree, I'd make a new panel and not trash the original. The easiest option would be a simple full vertical or horizontal panel cut out, like the Marshal or Orange option. "Aesthetically" though, I like the full rear panel with the rounded rectangle cutaway.