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Minimum thickness for speaker cab construction

Crescent Seven

Crescent Seven

Oct 27, 2005
569
9
Berwyn, IL
#1
I want to build that 12" airhead, but I'm broke like a joke.
However, I have AMPLE lumber, but it's all 7/16" OSB. Even properly braced, is this going to be too thin? I am going for lighweight...
I'd definitely make the baffle out of 3/4" ply, but what about the rest of the box?
C7
 
#2
The SWR Goliaths that I had were made of 5/8 plywood. IIRC, Bill Fitzmaurice suggests that 1/2 in. plywood is fine for his designs (but the internal panels do stiffen up the outside a lot).

If you can do strong joints at the corners (the top of the airhead would be the least easiest to add cleats to), I figure you could get away with it.

You could always search construction sites or the neighbors curb on garbage day...
 
#5
Crescent Seven said:
I want to build that 12" airhead, but I'm broke like a joke.
However, I have AMPLE lumber, but it's all 7/16" OSB. Even properly braced, is this going to be too thin? I am going for lighweight...
I'd definitely make the baffle out of 3/4" ply, but what about the rest of the box?
C7
Click to expand...
I have used 5/8" for bass cabs but my preference is 3/4" Marine ply or best of all Finnish Birch ply as this has the most durable exterior.
 
#6
since you say you're broke use 3/4 in poplar, light weight cheep and sturdy( I would use 3/4-1" Baltic Birch though) thin walls also allow a lot of sound to be heard from the walls , I would also treat it inside with insulation.

If you brace corners put a thin bead of silicon or wood glue for solid contact with no air pockets, then screw it in.

3/4 is optimum, but for a small cab I would even go to 1 in, I may be in minority here but dont get this "light weight thing"
SIZE MATTERS!!! Bass and weight go together famously.:D
 
#9
Jeff A said:
Glue about 50 sheets together and whittle out enough space to mount a speaker.

:rolleyes:
Click to expand...

Gimme a break, it's 1/16" thinner than 1/2", which if I'm not mistaken, is recommended by our own Bill F for his cabs.

Now, the reason I even asked the question is, I have a defunct vocal booth in my basement, and it's covered on the inside with 7/16" OSB. Rather than scrap all of this brand new condition wood that's cut in large, very usable pieces, I thought "hey, instead of going out and buying a $45 sheet of 3/4" plywood, perhaps I could make use of this material that I've already purchased." It's not illogical at all to wonder how well it might work.
I've built a couple of cabs, I understand that 3/4" voidless Baltic Birch ply is going to be an optimal choice. I'm also not trying to build a touring rig; I want to build a small 1x12 3 way cab with an airhead to mount my MAG300 in, that's light enough to carry with one hand. If the lighter, 7/16'' OSB would be acceptable for this application, it would behoove me to recycle what I already have into something I want to have. My main concern isn't necessarily strength, it's not going to get hammered on. I just want to know if it might sound "very bad" as opposed to "not particularly optimum".

With my planned dimensions, I'm not going to have large sides that will be unbraced; my largest aspect will be the back of the cab, which will be 20" x 24". I would cut the baffle from a piece of 3/4" I have leftover from my last project, for added stiffness.

Oh, and I just checked it on a whim. It's actually 15/32":spit:
C7
 
#10
If you really do have plenty of wood to play with, you could create some seriously un-resonant panels by glueing two sheets of 7/16th together with impact adhesive. It'll be one heavy mother of a cab, but what a sound!!!
 
#11
I think that 15/32" is within the thickness tolerance range for standard 1/2" plywood. :hyper:

I just built a 1/2" plywood cab for a 12" neo driver, following the many comments on this forum. There are cleats on the inside supporting the glue joints, and some bracing.

BTW the Eminence website has a set of reference designs for their new DeltaLite drivers.
 
#12
fdeck said:
I think that 15/32" is within the thickness tolerance range for standard 1/2" plywood. :hyper:

I just built a 1/2" plywood cab for a 12" neo driver, following the many comments on this forum. There are cleats on the inside supporting the glue joints, and some bracing.

BTW the Eminence website has a set of reference designs for their new DeltaLite drivers.
Click to expand...

I think the other rub with folks is that it's OSB, but from what I understand, OSB is going to vibrate less than regular ply...

I'm going to use a Delta 12LF, because it works very well in a small box. That or the Madison Knight 12" if it's all their T/S parameters crack it up to be.:D At less than half the cost of the Delta, it's tempting...

I've also decided to go 2 way with just a tweeter, because I have almost everything I need on hand to build it. All I'd need are the corners, etc, and the woofer. I have the tweeter from my Avatar, the crossover from the Avatar and the wood.
Hey, it's worth a shot. If it explodes and ends the world, I'll only be out about $100.:D
C7
 
#14
Yellow said:
since you say you're broke use 3/4 in poplar, light weight cheep and sturdy

I agree! Poplar is the way to go. Heres a qote from Euphonic Audio's web site.
"All of EA’s speaker cabinets are now built from imported Poplar plywood. Poplar gives the same structural integrity as Birch but with a 40% weight savings".
Other Manufacturers are also using poplar.
Click to expand...
 
#16
funkinbottom said:
Yellow said:
since you say you're broke use 3/4 in poplar, light weight cheep and sturdy

I agree! Poplar is the way to go. Heres a qote from Euphonic Audio's web site.
"All of EA’s speaker cabinets are now built from imported Poplar plywood. Poplar gives the same structural integrity as Birch but with a 40% weight savings".
Other Manufacturers are also using poplar.
Click to expand...
If poplar is as you say then that is the way to go, but for me only if it has the thick exterior layer that Finnish Birch Ply has otherwise it will have to be covered, one of the main advantages Finnish Birch is that although more expensive than other plywoods you can get away with painting/staining it which is a great time/cost saving issue and much easier for inexperienced cab constructors, and as I've said before a decent wood yard will offer the facility of cutting the sheet to your given dimensions, you walk out with a flat pack cab with just a few holes to cut with a Jigsaw.
Click to expand...
 
#17
120-B-09a.jpg


I built this 15" cab about 5 years ago, and use it a ton; it has a ply front and back, and the sides are sorta solid; they are something I found at my local Lowes that's basically a bunch of 3/4" x 1 1/2" strips glued together. I have an old EV B series speaker in it. The dimensions are pretty darn close to the size of an old Portaflex. I have a single 12 cab that goes with it (see pic below); they both fit in my trunk (unlike my 4-10), can be carried upstairs with one hand, and really get the job done, even if they do bleed a bit of sound from the sides.

musicmanset02.jpg


Of course, I never use that head live anymore!
 
#18
GreyBeard said:
I've never seen any cabs made out of plywood that thin and believe me if cab makers could get away with it they would. It probably won't work near as well as 5/8 or 3/4.
Click to expand...
I build all my subs from 1/2 plywood, spruce at that. I build my tops from 3/8 birch. They're stronger and less resonant than any commercial cabinet. But they're properly cross braced, which takes time to install. Commercial cabs use thicker materials and little, if any, cross-bracing. Using thicker materials is less expensive than the added cost of labor to install bracing, and that is why commercial cabs are built as they are.

But as for OSB, it doesn't have any properties that are useful for speaker building. If it did manufacturers would save even more money by using it. They don't.
 
#19
billfitzmaurice said:
But as for OSB, it doesn't have any properties that are useful for speaker building. If it did manufacturers would save even more money by using it. They don't.
Click to expand...

IIRC Hartke use it for their Pro line of speakers - the 4x10" with the big mid/high horn, and the vertical 2x10" and 2x12".

What are Ampeg now using for the SVT 810?

Alex
 
#20
alexclaber said:
IIRC Hartke use it for their Pro line of speakers - the 4x10" with the big mid/high horn, and the vertical 2x10" and 2x12".Alex
Click to expand...
I stand corrected. I wouldn't build a dog house from OSB, let alone a speaker. My dog deserves better, and so do my drivers.
 
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