BIB bracing

[jrenkin]

I am building a BIB for fx207es out of 3/4 birch ply.
It is a pretty big box, 8.5 x 12.5 x 81 inches inside dimensions.
I am thinking of bracing the front and back panels.
Should I bother?
Will it screw up the sound?

[Godzilla]

Yes double up the front and back. I feel the inner baffle provides enough of a brace for the sides from top to bottom. Enjoy!

Godzilla

[jrenkin]

Originally Posted by Godzilla

Yes double up the front and back. I feel the inner baffle provides enough of a brace for the sides from top to bottom. Enjoy!

Godzilla

I was thinking of building a cross brace to fix in the middle going from the baffle to the back and the baffle to the front, by cutting a wedge of ply riddled with holes like I have seen in other speakers. Think that would work, or should I double up? I didn't plan on it, so doubling will decrease the inner volume some, probably more than cross bracing.

[planet10]

Have a look in the bracing scheme in the iBIBk...planet_10 hifi

dave

[Leglandu]

From my FE168ES BIB building experience, I found vibrations at the following places to be reinforced :

Speaker area => added 2x10mm" of medium => just perfect

The higher third of the sides => too bad, I discover the problem after the building, so I tried to include carbon tubes => It works, just the right amount of vibrations at high level

The inner bafle : mine is too thin =>
I think it must be very rigid (compound materiel ?) to avoid "short circuit" for mediums & highs, letting them exiting at the top of the enclosure which is bad for the imaging !
I often think about cutting the back of my BIB to double the inner baffle and fill it with sand... not a joke !

Now, a good bracing "à la Planet10" planed before making is certainly preferable...

Sorry for my english, Babel Fish is my friend...

[chrisb]

Originally Posted by jrenkin

I was thinking of building a cross brace to fix in the middle going from the baffle to the back and the baffle to the front, by cutting a wedge of ply riddled with holes like I have seen in other speakers. Think that would work, or should I double up? I didn't plan on it, so doubling will decrease the inner volume some, probably more than cross bracing.

I think you're suggesting something like a pair of longitudinal holey braces on either side of the internal fold panel?

I'd be inclined to overlap them vertically somewhat, and offset them horizontally from the center-line, so as to distribute the bracing effect over larger area of the 3 affected panels.

Attached sketch of BLH for an 8" driver that shows what I mean


Hint: it's a lot easier to fit these braces before buttoning up the last side panel

[audioray]

chrisb
would you have the dem. for the box shown. would the fostex fe206es-r
work in these
thank you

[pjanda1]

I did a double thick front baffle. As you'll tend to hear resonances from the rear much less, I'm not sure a thick rear would be worth the weight. I also put a brace across the mouth, from side to side. It was maybe a foot long, and I cut a whole in the center. Not only is the mouth, and panels below it, on large BIB's ridiculously unsupported, but the brace provides a nice handle.

I thought of trying holey braces like I think you are suggesting. I'd seriously consider one in the mouth down to the bottom. It will provide much more stiffening than double thick panels. But, you still should consider doing something to address the sides, as they are larger and less supported.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

[chrisb]

Originally Posted by audioray

chrisb
would you have the dem. for the box shown. would the fostex fe206es-r
work in these
thank you

dimensioned sketch attached - note a couple of differences (double front baffle and tops), and excuse the metric

FWIW, these are for a quick & nasty pair of horns taken from a 2007 AudioXpress project, and no guarantees of performance are implied. From what I've heard from both 166 and 206ESR for which friends of mine have built the Fostex recommended BLH, I'd opine that no such thing as too much bracing for these drivers, but it could be possible to overdo the mass - even in plywood the result could well be excessive cabinet colorations from the lower mid bass down.

[jrenkin]

Chrisb-
Yes, that is very much what i mean. Sounds like it would work, but, yes, needs to be installed before the final side is put on. Not an easy aftermarket modification...

pjanda1-
I was kind if thinking that the side panels would be adequately braced by the long baffle running from top to near bottom. I guess at the very top, a side to side cross brace could help, but do you think it is really necessary?