Ply or Chipboard back pannel?

[revolver1]

Hi again, I was wondering if any one has any thought's about this.

I have a 1960BX cab loaded with 2x V30's and 2x G12T-75's, the rear pannel is made of chipboard. As I understand it some of the cabs of the 60's era came out with baltic birch ply backs and some had chipboard?

I've been thinking of getting some apropriate baltic birch ply and making a new rear pannel for the cab.
So here's what's got me wondering, Im guessing the chipboard will have more of a dampening effect and the ply would be more reflective or resonant. I'm thinking perhaps the resonance may be great with green backs but maybe not so great for the hyped up V30's. Maybe chipboard was used for good reason?

Any thought's?

[jnew]

Yep, been down this road. Particle backs are cheaper for production. (Good for Marshall's bank account) Tone wise there is a subtlety. Birch is harder, less absorbent and will resonate differently. More effective which translates to a little brighter and perceptively, maybe a little louder. The differences are not tremendous though. Either can sound great.

[rgorke]

If I remember correctly, most/many actually like the partical board backs better.

[Lefty Lou]

And the Mesa Boogie 4 x 12" cabs loaded w/Vintage30 Celestions have birch backs, go and figure.

[JimiJames]

Isn't the OP describing Marshall cabs?

[Lefty Lou]

Just making the observation that Mesa was using birch while Marshall was using particle board.

[revolver1]

Cheers fellas, guess I'm just gonna have to grab the bull by the horns and try it out see if I like it or not. At least it confirms what I had been thinking and its easy enough to change back If I don't like it.

[shakti]

I agree that the difference is subtle, and not as dramatic as some have made it out to be (as in you have to have a birch ply back, and it's the reason why late 60s Marshall cabs sound so good...it's the least of several factors IMHO).

FWIW, Hiwatt cabs starting around '71-73 (not sure of the exact time) have very heavy particle board backs, sound killer, and Hiwatt aren't exactly known for cutting corners, quality-wise. I'm certain it was a tonal decision on their part, to have as inert a cab as possible. Early Hiwatt cabs had ply backs though.

[revolver1]

I'd read a few posts (not here) and people were rubbishing the state of the interiors of modern Marshall production cabs. Mine for instance has alot of over spray of black paint around the inside.

I've seen the inside of quite a few 60's era cabs on the net and they are all pretty clean. I know alot of things modern era Marshall has done has been on the cost cutting side of things but on this occasion I think they have done it deliberately to deaden the reflective surfaces of the cab. I geuss like most things neither one is wrong just different and it's a case of wich one you prefer.

Honestly I'm a bit skint at the moment but when I'm a bit more flush I'm gonna give it a try just to see and I'll report back Always seems to be when I'm a bit skint my mind starts wondering to subtle improvements... Ha Ha. Another one is that my cab has a screw through the back pannel going into the sound post, I've read this was to eliminate unsimpathetic vibration. Correct me If I'm wrong but I beleive the 60's era cabs had a rubber patch on the end of the sound post pressed up against the rear pannel. Theres probably gotta be another subtle differance there too.

I'm all about vintage tone but It's good to keep the mind open. Some of thease thing were done for good reason I guess.

Jnew, you'd said you've been down this road before. Just out of intrest which way did you go in the end? And why?

[jnew]

I have a Marshall 1960B, particle back with Jim Seavall's (M75 PVC's) as my favorite right now. It's the cab used in all the clips in my signature link. Next week when I get back home, I'm picking up my new Divided by 13, 4X12 built to 68 spec's with the Baltic Birch all the way, through and through. I will move the speakers from the Marshall to the Divided by 13 and make before and after clips. This will be a true representation as both cabs also use the Marshall Cane grill cloth. And the cool thing is, recording always seems to divulge little things that we don't catch while we're busy playing. When we're focused in our listening and not pre occupied picking our noses, or guitars, those little subtleties tend to stand out. But to answer your question, I've always liked cabs with Birch ply backs a little more for their slightly more live resonant feel and tone.

Regarding the sound post. I too put a screw through the backing and into the post. I also shimmed up that post about 1/8" so that the back had a hint of a bow when tightening the screws. The thought here was to not have flat, straight surfaces at the front and back where standing waves can be overkill with funny overtones and stuff. It also insures that a solid connection would eliminate and rattling in case the post just wasn't quite long enough. But to be honest, regarding the standing waves, I'm not sure this helps too much, if at all, as the angle of the baffle board has an actual lean from front to back. (even the straight, or B cabs) whereas the back is square. It would seem that it should be more than enough to offset any symmetrical standing wave issues. But at least I know there will be no rattles.

[JimiJames]

"...In my tests I found that the 3/4" birch was less lively than the 5/8" birch, so that's why I switched to it. In pine combo cabs I like the 3/4" better than the thinner pine stock, as it helped restore the bass response..." 06-18-2010-TGP

Re-wire with thicker speaker wire (search threads on gauge diameter)
Solder connections. No connectors

-Tighten all screws.(DO NOT over tighten the speaker machine screws to avoid bending frames.) (Cheese heads are a nice touch.)
-Metal handles always a plus. Maybe even a gasket under the flange...
-Decide on casters... or not. (if off or on the floor)

The only thing I ever did to the outside of a cab, that actually made a difference cost about $0.36. Put a screw with a washer straight into the back to pull it tight to the wooden pole piece that is only attached to the front with a few screws. Took a bit of "boominess" out and gave a tighter compressive sound.

-Check center soundpost and decide if you prefer the center screw. Marshall used them later on... Some even remove the post altogether... YMMV

[revolver1]

Thank's jnew I look foward to the clips. And thank's also JimiJames that's a good little round up, gives me a bit to think about.

[jnew]