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Please bring me up to speed on current thoughts about DIY subs - Page 2

post #31 of 35
Thick walled construction comes in beneficial when you need mass to keep the enclosures from moving with really high Xmax drivers like the LMS Ultra and RE XXX 18". Both of these drivers can push around a lighter box, you really need a heavy box and good feet to keep them in the same place. The exception of course is to do a dual opposed sealed, use the drivers force to keep the enclosure in place.
post #32 of 35
Quote:
Originally Posted by duc135 View Post

+1

Bob,

Here are some pictures of the bracing I use for my current build for a pair of 15" subs made from scrap pieces of 3/4" MDF. At close to full tilt at the limits of excursion, I can barely feel the cabinet walls vibrating while the floor and house are going nuts. My enclosure is 26" x 19" x 19" and the bracing adds only 4.5lbs.






Yes! I'm new to subwoofering, but most of the sub builds I've seen here look not only under-braced, but incorrectly braced. Bill Fitzmaurice probably has measurements proving how audible different wall thicknesses and bracing designs are, and his bracing scheme is a lot like yours, maybe just without as many "sticks", and with pieces sticking out on all sides rather than running along the wall itself (if that makes sense). Did you mean to say that your cab is 26 X 26 X 19? The structure appears to be 26" high, 26" and 19" in the other two planes. Other designers use more bracing than others, Jim Salk and Danny Richie, for instance. In the 50's the big speaker cabinets often had chambers filled with sand, a cheap way to damp cabinets. Also very effective, as well as heavy as h**l! My cabs are 18W X 24H X 24D and I braced like you, three rows of three left to right, two rows of three top to bottom, and two rows of three front to back. All connected where they cross each other. Maximum unbraced span 5.5" in every plane. About 0.5 cu.ft. of bracing, for a single 15. Walls 1.5", baffle 2.25". Overkill?
Edited by BDP24 - 9/12/13 at 9:08am
post #33 of 35
overkill is under rated, but really 7-12 inches depending on thickness of the cabinet is all that's really needed as spacing for braces...
post #34 of 35
Quote:
Originally Posted by BDP24 View Post

Yes! I'm new to subwoofering, but most of the sub builds I've seen here look not only under-braced, but incorrectly braced. Bill Fitzmaurice probably has measurements proving how audible different wall thicknesses and bracing designs are, and his bracing scheme is a lot like yours, maybe just without as many "sticks", and with pieces sticking out on all sides rather than running along the wall itself (if that makes sense). Did you mean to say that your cab is 26 X 26 X 19? The sticks appear to be 26" in the vertical, and 26" and 19" horizontal. Other designers use more bracing than others, Jim Salk and Danny Richie, for instance. In the 50's the big speaker cabinets often had chambers filled with sand, a cheap way to damp cabinets. Also very effective, as well as heavy as h**l! My cabs are 18W X 24H X 24D and I braced like this, three rows of three left to right, two rows of three top to bottom, and two rows of three front to back. All connected where they cross each other. Maximum unbraced span 5.5" in every plane. About 0.5 cu.ft. of bracing, for a single 15. Walls 1.5", baffle 2.25". Overkill?

My box is 19" x 26" x 19" H x W x D. The bracing is 17.5" x 15" x 17.5". I had to make a "hole" in the bracing to allow the driver magnets to recess into the bracing structure. I didn't brace the front or rear panels since my box is a dual opposed design. There was nowhere on those two panels that needed bracing. There was at most 1" of space between the driver cutout opening and the side walls other than the corners. Not only that, but the baffles were also 3.25" thick to accommodate recessing of the 1.5" tall driver gasket. Like you, I don't allow for more than a 5" span not including the diagonals. Overkill is better than insufficient so long as you take displacement of the bracing properly.

The advantage of my bracing is that I can use scrap pieces of MDF instead of having to take bracing into account when purchasing panels. Any scrap pieces of MDF greater than 3/4" wide is kept for cutting into pieces for bracing (and homemade Jenga pieces wink.gif ). The disadvantage is the time it takes to make all the cuts and gluing them all together.
post #35 of 35
Ah yes, now I get it. Excellent!
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