Rebuilding/repairing/stabilizing speaker box on STD4

[andylevine]

The bottom of the back panel of the speaker box on my Mardi Gras is crumbling away!!   See pic:


imgur.com/a/Jd5Qb9K


Is there a way to remove just the back panel and replace or are these all glued up making that difficult? Short of throwing on my table saw any other suggestions to repair or stabilize would be appreciated.

Also, I noticed the box was lined in some places with fiberglass insulation, and bare in others.  Was this the case when these boxes were new, or was the insulation on all surfaces?  I don't really want to change the expected acoustical properties of the box.

Thanks
Andy

[Ron Rich]

Hi Andy,
How heavy is your table saw-- maybe you will need to get some help, on accountacause, I see no other way---??--as for the fiberglass--yes, that was "strategically" placed to control the audio. Ron Rich

[robnyc]

Andy, I've used a heavy coat of weather grade polyurethane to stabilize the crap board. Then a full length of corner bead to protect the frayed end and serve as a clamp to holds it together. You will need to use screws long enough to go through the bead and defective board and into the wood that is at a right angle. In this case it would be the floor or bracing inside the speaker cabinet.

It's a shame Seeburg used what is essentially sawmill waste for their cabinets, but they were not alone in this....

Rob

[Ron Rich]

Rob,
I got into "an argument" with the "production foreman" and one of the audio engineers, about the "crap board", that Seeburg used. They claimed it was "more expensive" to use what they were using then to use "plywood". They both claimed that the "crap board" they were using was done for it's acoustic properties Ron Rich

[andylevine]

Thanks, Ron and Rob... yeah i was really surprised when I saw they were using particle board. The M100B I did was good solid ply and built REALLY well. When I finally liberated the speaker box from the STD4 metal carcass, the front speaker holes crumbled in my hands :-O Luckily, I have a good woodworking shop in my basement and remaking these bits will be easy. I'm in no rush...its a hobby! The question becomes do I stay true to how it was built and remake using particle board or go to what they probably would be using today, MDF. Some good friends of mine who are in to ultra high audio swear by the stuff for speaker cabinets.

[robnyc]

Andy, Ron the argument (really excuse)for particle board was that it was less prone to resonance at high volume levels. MDF is actually a "wood alloy" -a few steps up from particle board. Both these materials have two things in-common: they are rigid and a b---h to cut.

In speaker enclosures one can use almost any grade of wood IF it is braced enough. The advantage to crap board is its stiffness makes for simpler-cheaper construction since it needs less bracing for acceptable performance.

FWIW: As in amplifier rebuilding, since we are dealing with a one-off and not mass production, you can take care to use the best components for the task w/out considering cumulative expenses. For the wood, just do a little research as to what is recommended for enclosures of similar size and go with that.

RobNYC

[Ron Rich]

Andy,
Your M100B was made of the cheapest wood they could find, at the time--I don't know "woods" ( My wife banned me from using any kind of "wood working tool-- and I'm really happy about that !), but I was told it was "gum wood" ?? Also said to be extensively used in pinball machines ??
Ron Rich

[paradisecs]

I'm not a jukebox expert but I do have a wood shop. Chipboard (particleboard) is glued sawdust pressed back into shape, very dense and heavy, and great for sound but doesn't hold up to moisture and the edges chip easily. I've refinished cabinets that have done this by sanding it down then floating a coat of wood filler across the entire panel, then sanding smooth again. Then gluing & nailing/screwing a 90 degree metal flashing (like used on roofs) to the bottom edge to protect it. If not restoring to be original for value it could be a way to fix the problem if all that is wrong is the edges.

Stephen

[Ron Rich]

Gentz,
My shop (NOT me !) did the same thing on hundreds, of re-built LPC, and PFEA model Seeburg cabinets. We installed 3/4 inch angled aluminum strips, painted to match the Decarlite, colors, as those cabinets always got chipped on the bottoms. I think that looked real good--and so did the customers we sold them too-- Ron Rich