Enough bracing?

[Vikash]

I'm building this at the moment but I'm not sure if I can get away with this little bracing (run out of mdf). And if I do only use one brace can someone confirm this is the optimal place to put it.

[rho]

I would not put it exactly in the middle of the box. Put it at 3/5 or 4/7. This makes the reconance of the part in front of the brace different from the part behind the brace.

[mcp]

And watch your ratios.

[Centauri]

I would be inclined not to brace top to bottom, as these are the most rigid panels. The baffle will be the weakest, especially between the woofers. I would suggest a similar MDF arrangement to yours but front-to-back, one between the woofers (with cutout around the tweeter) and another one lower down. A brace can also be run between the lower crossbrace and the upper port to support this.

Cheers

[Rarkov]

Why not place it diagonally. I mean from bottom Left to Top right.

That would give you the best of both worlds.

Gaz

[Vikash]

Just came across this thread:

It has been shown that while just about any bracing helps to stiffen a box, the best way to brace is along the vertical dimension. That is, a box that is two feet high by a foot wide by a foot deep should be braced with two foot long braces running top to bottom on the inside. One foot long horizontal braces are not nearly as effective. This has been studied in an article in the Journal of The Audio Engineering Society. - Kelticwizard

I've read this before as well. Argh. Gonna have to do some reading now...

Ok, what about the holes in the brace? I was actually thinking about like 20 x 8cm dia. holes. How do I know when there's enough space for the cabinet to breathe through the brace without negative effects?

[getafix]

Originally posted by Centauri
I would suggest a similar MDF arrangement to yours but front-to-back, one between the woofers (with cutout around the tweeter) and another one lower down. A brace can also be run between the lower crossbrace and the upper port to support this.

I tend to agree with this rather than putting the brace parallel to the long panels, which tends to flex more than short panels.

[mcp]

You may want to check your internal ratios (WxHxD). Looks like you will have some nice standing waves with your present dimensions.

[navin]

Originally posted by Centauri
I would be inclined not to brace top to bottom, as these are the most rigid panels. .. I would suggest a similar MDF arrangement to yours but front-to-back
Cheers

i agree with this. front to back below woofer and behind tweeter should help most.

[planet10]

If there is only enuff material for a single brace then you have it right... do make sure that the brace divides the panel unevenly... a ratio with an irrational number is best.

The side panels are the largest and will resonate at lower frequencies than any other panel, so they are the most important to divide up.

If you can slant the brace so as to divide the side panels into non-rectangular shapes even better.

perhaps you can use some of the materials from the holes to brace the back of the woofs against the brace -- you could line up the "not hole" part of the brace to facilitate this -- if you can run the woofer braces all the way to the back (ie a 2nd bit from the brace to the back, even better.

Mounting the drivers push-push would be even better, then you can have active vibration cancellation.

dave