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Dummy's guide to adding bracing, help

M

morewattsplease

Apr 29, 2012
123
0
libertyville, chicago
#1
I've got an emperor 4x12 staggered vertical, and I love it. Its got guts, its loud, its gorgeous.

However. I do want to address vibration issues, and I would like to experience the benefits of adding bracing to an emperor that others have said they experienced.

Please don't flame emperor, I like my cabinet a lot, its really pretty, it probably won't be my last cabinet purchase but i don't think I'll ever sell it. I want advice on this subject, not to be told to use a time machine and not buy it.

I don't want to drill through my cab if it can be avoided.

I've looked at other things here about bracing, but I'm a real noob on this stuff.

Where does the bracing go, how do I attach it to the cab's inside if I don't want to drill (if possible), what materials will I need...
I looked at greenboy, and I can't yet figure out how to apply his diagrams to a non fearful design

I'm gonna keep trying but some basic plain language advice will be appreciated.
 
#2
You need to look inside to determine where the bracing needs to go.

Most likely you will need to remove all the woofers to work on it safely.

The easiest after-market bracing to add is dowels usually.
 
#3
If it's 3/4" plywood construction I'd use braces made from 1/2" birch that's 1.5" wide glued longitudinally and latitudinally spaced around 8" apart.

You glue the 1/2" side to the walls of the cab as you see in the Greenboy diagrams. Don't bother using braces in the corners, that's already the strongest part of the cabinet.

You'll have to clamp or weigh them down to make sure you have good contact for the glue between the wall and the brace if you're not using screws.

Lots of people here like the PL glue but I generally build my cabs with good old carpenters glue. There's pluses and minuses to each adhesive but both will work well.

You can also use 3/4" diameter dowels to cross-brace. My opinion is you don't need to space them as closely as the wall braces, so if your cab is about 14" deep, 16" wide, and say 48" tall I'd just do two or three going from the sides and one from the top to the bottom. Then two or three going from the back connecting to those.

Hopefully someone will chime in with a very good computer generated drawing that's running around here showing this bracing scheme.

Good luck.
 
#5
morewattsplease said:
If I add this:
http://www.foambymail.com/EC1-5-F-CH/1-5-eggcrate-foam.html

If I line the walls of my cab with that, probably velcro it down or staple, would that be beneficial? Or do you guys think that will make my cab's sound really dead/muted?
Click to expand...

lining the cab is a very good idea and that will work fine. There's also polyfill, you can find it at craft and sewing stores, just an inch will do.

I recommend stapling or gluing whatever lining you use.

If the bracing scheme I outlined earlier seems like too much, RPSands' suggestion will do fine, too. I tend to like my cabs very well braced, esp if they're going to be putting out the SPLs.
 
#9
I like the batting mentioned earlier. I got enough to do two cabinets with some left over at a fabric store. It's like the insulation they used in the old cabinets, but it's not fiberglass and won't cause itching and handling problems. Use a bunch of it and staple it in. It won't cause your cabinet to sound muffled. I would do the bracing project first, then the batting, then put it back together and enjoy it forever!
 
#10
I helped a friend brace his cabinet once. We measured as close as we could and then cut 2x2 sticks about 1/4" too long. Then we gradually sanded the ends down until we had to really pound hard to get the sticks into place. This made the cabinet walls flex a bit but it put them under tension so vibrations would be minimized. We put three sticks in the box, one for each dimension, and roughly in the middle of each side. That really stiffened up the box and clarified its sound. Since we used 2x2s it added a few pounds but he thought it was worth it. We also surrounded the ends of each stick with glue to hold them in place.

You could use 1x1s or dowels also. We used 2x2s because they were available and they were stout enough that they won't bend very much.
 
#11
bracing.jpg I believe BFM came up with this as an alternative to fEARful style bracing...Good Luck...
 
#12
you can glue/screw front to back braces on the cabinet sides then glue/screw cross braces to those... the cross braces will need to be a very tight fit to be fully effective..you can follow the same approach for any other facing surfaces you desire...ie front/rear & top/bottom

Additionally, consider dampening the cabinet surfaces with bitumen..you can buy expensive panels for this or simply use car underseal... paint several coats on (say 1/4") and your cabinet will be dead as a rock..leave to vent for several days before putting drive units back in

fyi the foam in your link will do NOTHING to solve cabinet vibration... foam/batting will not work at low frequencies but will reduce (dampen) standing waves at mid/hi frequencies...you can however line the interior surfaces with this or if you get the softer stuff simply fold it into place in the cabinet body leaving room for the drivers.

If you plan on keeping your cab, its worthwhile doing all three. not expensive, just time consuming
 
#13
mystic is the first I've heard of the car underseal idea

the permanency of this scares me, anyone care to second his motion to do it? I'm planning to do the dowels or something simillar this week and in the meantime examine my options for the foam or underseal, its just that with the underseal not being something I've heard before I'm a little skeptical
 
#14
Agree on the BFM bracing. It's simple and the best. You may or may not need that many.

If you don't want to drill the cabinet for the dowel, or if the cabinet if MDF - then don't drill it.
You can cut glue blocks. 3/4" poplar would be fine. Drill holes in the blocks for the dowels. Dry fit.
Then glue the dowels in the blocks and glue and screw the blocks to the sides.
Here too, don't use nails for MDF - it will just crumble.
 
#15
MDF?

My plan is to do the dowels/2x2/1x1's, do some mattress/acoustic padding, and close her back up.
For now I will pass on the undercoat sealer, and in general do...not minimal changes, but a little before I do a lot. Both because I am not an expert at this, and because I am 80% satisfied with my cabinet. I just would like to see what I could do to make it better yet leave room for responsible back tracking if I don't get the results I would like.
 
#17
Bracing cabinets is vital for best performance, here is the extent my son goes too with an eminence 3015lf for studio monitor LF use.
You save weight in the magnet so don't skimp on the cabinet even for live work it matters a lot.:bassist:
Link Removed
Link Removed
Now that's a proper enclosure.:bassist:
 
#18
Done the bracing with 1" dowels, did not pad for a couple reasons (money being one)

Two side to side, two up and down, and there was already front to back so for now I didn't add any more front to back.
It sounds great, low end sounds more thick and easy, and the high end is clear and less shrill.

Thanks for all the help everyone
 

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