Bracing speakers - Newbie question

[Alain]

This may sound studid, but I would like to know if I braced my speakers with braces 20mm by 30mm would be sufficient. I am concerned that such thin braces may vibrate. On the other hand, I don't want to use braces which are too big as not to change the internal volume. I plan to make them like internal crosses.

[joe carrow]

Originally posted by Alain
This may sound studid, but I would like to know if I braced my speakers with braces 20mm by 30mm would be sufficient. I am concerned that such thin braces may vibrate. On the other hand, I don't want to use braces which are too big as not to change the internal volume. I plan to make them like internal crosses.

Any size of brace will change the internal volume; it's best to just increase your box size to acommodate the braces.

Try searching the forum for various subwoofer projects... perhaps threads involving "tempest, tumult, sealed sub, large sub, subwoofer bracing, internal bracing"- you get the idea.

I don't know if you ever saw this- but B&W uses an interesting bracing method for their large speakers.

B&Ws 'Matrix' bracing

It's like this; the braces brace each other. You'll see a lot of this in large sealed sub projects- but on a scaled down level, because who can CNC cut their braces? Oh, and note that B&W mentions damping the braces with open cell foam. I don't know how extreme your project is- but I think the ideas are out there for however far you want to take it.

Good luck!

[BillFitzmaurice]

I personally believe that any brace that does not extend from panel to panel with a full 'shelf' conmfiguration is hardly better than no brace. The brace doesn't have to be thick (13 mm will do) or solid (in fact holes to lighten it and minimize reflective surfaces within the box are preferred) but it should eliminate any free panel area wider than 15 cm on one plane. It's OK if the panel is two meters unbraced on one dimension; so long as the other sees full shelf bracing at that maximum 15cm apart you won't have a vibration problem. If you're concerned about internal volume you can drill the shelf full of holes ala Swiss cheese and it will still do its job.

[tiroth]

Originally posted by joe carrow
Oh, and note that B&W mentions damping the braces with open cell foam.

Actually this is what they say:

each cell is filled with absorbent wadding, usually open-cell foam

That is not simply damping the brace, it sound more like quasi-aperiodic loading. I would guess the foam used is very thin, but still it must be providing some damping. Try breathing through 2.5" open cell foam -- there is considerable resistance to airflow.

[DIYNewbie]

I have a question that kind of follows along the same lines... I am building a cabinet for my tumult sub. The exterior dimensions are 20" x 20" x 20" and the walls are 1.5" MDF. Does this box need bracing or is it sturdy enough as it is? Also, is there an advantage to lining 5 of the 6 interior walls with black hole 5?

Thanks.

[bogoes]

You will definately need bracing in the Tumult sub, regardless of 1.5" walls. I would go with the Adire method of bracing, see link here for Tempest example, it is essentially two vertical shelf braces full of holes, and they form a cross in the box.

I would not bother spending another huge amount of money on BlackHole 5, not for a sub anyway. If it is sealed then stuff it with a bag of AcoustaStuff or some polyfill from Walmart. If it is ported, then you MIGHT want to put some open-cell egg crate foam on the walls, also available from Walmart, and for A LOT less than BH5 - I just don't think you'll notice a difference worth justifying the cost. With 2 massive cross braces and 1.5" thick walls, panel flex should not be an issue.