How much bracing is necessary?

[Frosteh]

I have a 16.5"x16.5"x16.5" sealed enclosure for a single 12" driver. I'll be pumping a fair bit of power into it considering I'm running a Linkwitz Transform to boost output to be flat to nearly 20Hz. I've used 1" MDF panels, and I'm wondering how much to brace the internals. I've got enough extra MDF to do some extensive cross bracing similar to this setup:

NOTE: This is NOT my subwoofer. Mine is sealed.


Is this overkill or necessary. I can do any amount in between as well. Is a dowel enough or do I need something extensive like this?

[revboden]

the pic is just about right

how do you fit a 12" driver in a 16.5inch^3 box? that's like 2.55" x 2.55" x 2.55"

[Frosteh]

Originally Posted by revboden

the pic is just about right

how do you fit a 12" driver in a 16.5inch^3 box? that's like 2.7" x 2.7" x 2.7"

Oops. I meant 16.5"x16.5"x16.5". Fixed in original post.

[revboden]

yeah, i figured. bracing like the picture will be good in a 16" cubed box the small 8"x8" open panel area will only vibrate at frequencies well above the output of the driver.

[Frosteh]

Originally Posted by revboden

yeah, i figured. bracing like the picture will be good in a 16" cubed box the small 8"x8" open panel area will only vibrate at frequencies well above the output of the driver.

Where are you getting an 8x8 area? I don't really understand.

[revboden]

take a 16" square and cut it into 4 sections like in the picture above. each open area (undamped) will be 8" by 8" the resonance of a 8"diameter circle (to calculate resonance you have to think in circles that will fit in a space) is right around ~1041Hz well above the frequency range of the driver.

[chrisb]

Originally Posted by revboden

take a 16" square and cut it into 4 sections like in the picture above. each open area (undamped) will be 8" by 8" the resonance of a 8"diameter circle (to calculate resonance you have to think in circles that will fit in a space) is right around ~1041Hz well above the frequency range of the driver.

Try using 2x4 solid lumber (non-finger jointed wall studs) for bracing - it's much stiffer than MDF, or locate the window-pane bracing off-center by at least an inch or two to sub-divide the panels into uneven areas.

[Pallas]

Originally Posted by Frosteh

INOTE: This is NOT my subwoofer. Mine is sealed.

That's way overkill. It will only rob you of efficiency (due to lowered box volume) and make the sub heavier than necessary. So sonic or practical benefit.

For a sub that size in 1" MDF, you don't need anything more than maybe a dowel connecting the side walls. Depending on the size of your driver's motor, you may also want a shelf brace to support it.

[Frosteh]

Originally Posted by Pallas

That's way overkill. It will only rob you of efficiency (due to lowered box volume) and make the sub heavier than necessary. So sonic or practical benefit.

For a sub that size in 1" MDF, you don't need anything more than maybe a dowel connecting the side walls. Depending on the size of your driver's motor, you may also want a shelf brace to support it.

Are you saying for a sub the size in the picture or for my sub? I just finished routing everything and I'm contemplating whether or not to brace at all. 1" MDF is rigid as hell and I don't think it's going to go anywhere, even at <20Hz. A dowel just seems so cheap, though.

[revboden]

at 20Hz it won't move at all at 62.5, 125, 250, 500Hz it will ring like a bell. you have to think about harmonics. what crossover point are you going to use?