Brace yourselves (pun somewhat intended)

[crazyjpeters]

Hi All,

Just wondering what the consensus is on tower cabinet bracing. Most, except for some extreme looking boxes, are using a few shelf braces. Most are window style with rounded edges. I've seen very few boxes with vertical bracing (think same plane as either front baffle or side (Swiss cheesed of course). Any reason why? Are shelf braces that much easier to work with?

[5th element]

It's to do with increasing the frequency at which the panels will resonate at.

For example if the side of the loudspeaker in a tower resonates at say 400Hz, then in a very basic way, placing a horizontal shelf brace across the middle of the panel will halve the area that's free to resonate and this will push the frequency up to ~ 800Hz.

Larger panels resonate at lower frequencies so using many horizontal shelf braces splits the sides of a tower up into relatively small individual parts. The idea is to get the resonance up high enough in frequency so that the driver cannot excite it. For example, if your mid/bass is only going to cover up to 2000Hz, if you have a panel resonance at 4000Hz it doesn't matter because the driver is rolled off significantly before it and therefore wont excite it.

The reason why vertical bracing is seldom used is because cabinets tend to be tall and thin meaning the surface area of the top panel is usually quite small and hence it will resonate at quite a high frequency as compared to the sides. It all really depends on the size of the box.

[JonMarsh]

Somethings to think about...

For a long rectangular panel, the best bracing approach is to minimize the unsupported span. This is most effectively done by a long brace running the length of the panel; offsetting it slightly will spread the resonance out, so that you don't have two sections of equal dimensions.


Same goes for front to back.

this is probably why Avalon uses this approach, with a side to side vertical brace and a front to back vertical brace.

If you have to put holes in the braces, circuits are better than rectangles, because arches are stronger. Look at Rennisance architecture. Those guys weren't dummies.

[dsrviola]

I remember reading an article that B&W came to the same conclusion, Jon: tower speakers benefit most from vertical braces.

[5th element]

Ah I see what you mean. I was looking at it in terms of having the vertical brace sit in the same plane as the sides, in other words it wouldn't break up the side panels at all. Flip it so it runs up the centre of the side panels and you've got a completely different set of circumstances.

[fbov]

And with some interesting science behind it...

http://www.audioholics.com/education/loudspeaker-basics/detailed-look-proper-loudspeaker-cabinet-bracing

[Carl V]

My first foray into DIY was NORTHCREEK
(borealis, Rhythm & Leviathan)
I still build enclosures along those lines.
double up on the front & back panels.
Long Vertical brace (asymmetrically placed)
or braces. one horizontal brace between tweeter
& woofer. Window pane or circle cut outs.
I have since added a supporting brace for
the mid woofer or woofer magnet as per SL.
SL also makes mention of panels >4 sq"
should be supported....if I recall. BB ply.
And it need not be volume robbing 3/4'
BB-Ply all the time in all locations...imho.

[meb46]

fbov - there are some really interesting articles on that website... some very detailed mathematically, and some just great "Myth Busters"... some sales people I have spoken to over the years could seriously benefit from the following article...

http://www.audioholics.com/education/loudspeaker-basics/loudspeaker-cabinets