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Adding bracing to a cabinet

NKBassman

NKBassman

Jun 16, 2009
16,500
32,881
42
Winnipeg, MB, Canada
#1
So I have this 2x15 cab that I want to reinforce with some bracing, to cut down the vibration on my precious tube amp, which usually lives atop this cab.

Because the speakers are mounted to the inside of the baffle and the back panel is removable I can't do too much with cross bracing, so I was going to add rib/spine braces instead.

Few questions before I get started:

1) is it typical/necessary/good practice to brace the baffle as well as the walls?

2) How big should I design my rib braces before they just start adding weight? I was thinking of using something like 1/2" x 2" tall ribs at 8"-12" o/c for the walls, and tighter spacing for the top.

That's all for now.

I'll post some pics of the inside of my cab when I get home.
 
#3
This is the best way to brace a cab. You can use dowels as shown or 3/4 x 3/4 inch stock, even 3/4" plywood strips. Rib bracing is relatively ineffective by comparison.

bracing.jpg


With a removable back add spines across the back opening, cross brace those to the baffle, screw the back to the splines.
 
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#5
@WingKL: Thanks, I really have to learn how to use that Google search feature...

@Bill: I've seen that pic floating around a lot and I will add x-bracing where I can while still leaving myself room to remove the speakers. Thanks for the tip on the back, but I'm not sure if I want to go drilling a bunch of extra holes in the panel since it's finished in stain, not tolex or rat fur or anything. I'll think about it... lots to do before then.
 
#6
NKBassman said:
Thanks for the tip on the back, but I'm not sure if I want to go drilling a bunch of extra holes in the panel since it's finished in stain, not tolex or rat fur or anything. I'll think about it... lots to do before then.
Click to expand...
Considering how many people will be looking at the back of the cab I wouldn't be giving cosmetics the priority over results. It looks like there's already baffle to back bracing anyway, I'd add a 3 to 4 inch wide piece of plywood to connect those two braces. But that's if you want to keep the cab. You'd get a better result with a monocoque cab with front loaded drivers. Doing so allows the cab to be well braced with minimal weight; as it stands now all those cleats in the cab corners have no structural benefit, they're just added weight, and if that same amount of material was employed as cross-bracing you'd get a much better result with no additional weight. And if you do rebuild put the port in the middle of the baffle, to add strength where it's most needed.
 
#7
Thanks again Bill. Good points.

I'm not going to be rebuilding this cab, but I do have some speakers laying around for a home build sometime in the future. That's a whole different thread that I'm sure you'll have plenty to scold me on as well :p.

I'll follow up once I've made some progress.
 
#9
Finished with the bracing. Went pretty overboard, especially on the top panel where the amp sits, but results are night and day.

There is now no discernible vibrations for anything sitting on top of the cab (even loose change pretty much stays put). This is what I was hoping to achieve, so mission accomplished at this point.

I'd have been satisfied if that was the only change, but In addition i've also found the overall tone is improved (I'd say "punchier" and less brash in the mids). Cab is also now more responsive to EQ and volume changes. I think it's louder too.

It is a fair bit heavier now, but it's still lighter than my old cab, and I can still load it into my car myself, so it's all good. Two-man carry is still a joke compared to some other cabs I've moved.

Pics of what I did are coming as soon as I get my computer back from the repair shop.
 
#10
NKBassman said:
Finished with the bracing. Went pretty overboard, especially on the top panel where the amp sits, but results are night and day.

There is now no discernible vibrations for anything sitting on top of the cab (even loose change pretty much stays put). This is what I was hoping to achieve, so mission accomplished at this point.

I'd have been satisfied if that was the only change, but In addition i've also found the overall tone is improved (I'd say "punchier" and less brash in the mids). Cab is also now more responsive to EQ and volume changes. I think it's louder too.

It is a fair bit heavier now, but it's still lighter than my old cab, and I can still load it into my car myself, so it's all good. Two-man carry is still a joke compared to some other cabs I've moved.

Pics of what I did are coming as soon as I get my computer back from the repair shop.
Click to expand...

Nice. :) Those are just the results you should be having with extra bracing, including added volume. Now, lots of guys discounted Bill's advice, but he knows his speaker building, and you've now seen what some extra attention to smaller details can net you. Congratulations. Did you also line the cabinet?
 
#11
BurningSkies said:
Nice. :) Those are just the results you should be having with extra bracing, including added volume. Now, lots of guys discounted Bill's advice, but he knows his speaker building, and you've now seen what some extra attention to smaller details can net you. Congratulations. Did you also line the cabinet?
Click to expand...

Yeah I lined it using standard 1.5" fiberglass insulation. Top, sides, and back panel.
 
#12
The only other thing I've done besides similar to Bill's advice is to paint the inside with fiberglass resin with a tad extra hardener and the outside with same except included a layer of fiberglass cloth with resin over it....followed by a epoxy paint. Serious cabinet weight gain(like moving large rocks instead of boxes) but these were PA subs & low mids(i.e. handtrucks, wheels on the 18's cabs, and road crew). A vs B was HUGE gain in output.
 
#13
Yep. Any of these stiffening techniques results in stiffer boxes which results in more output. There's a lot of speakers that could be louder than they are if everything the driver was doing ended up at your ear as sound instead of vibrating flimsy boxes.
 

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