Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks?

[Godzilla]

I plan to make a ‘grill cover’ on the top of my BIBs. One for the top and one to cover the driver.

As for dims… we left them the way they are so builders can make what suits their fancy. If you want specific dims post which driver and we can offer suggestions.

Godzilla

[lousymusician]

Originally posted by peterbrorsson
Lousymusician,
Nice pine you have there. How thick are panels and I suppose you have not started playing with damping yet?
In my experience with pine is that you get the same result with chipboard. Of course pine is better due to one can get nice edges almost for free.
I got a huge difference moving my BIBs from a hard ceiling to an acoustical treated ceiling (meaning normal office plates in ceiling).

It will be interesting what stuffing you will end up with.

Best regards Peter

Panels are 3/4 thick. I stole some poly batting from my wife's sewing stash. I cut a strip the width of the enclosure, and ran it from the point above the driver, down the internal panel with a strip of 2" double stick tape to keep it in place. It ends maybe 8" below the driver for now. I'll lay some more of the same in the bottom, once there is an actual bottom. I figure the driver will need some playing time before final tweaking.

I didn't mention last night that with the single thickness baffle the FR125 magnet hits the internal baffle. I had to route out a recess for it, stepped from 1/4" to 1/2" deep.

[uvellani]

Did you notice any improvement in the mid-range with the poly batting? If that was what you were after with that. My experience with batting was not very good. I found that it absorbed some of the low freqs and let the upper freqs through. In fact if you take a piece of it and hold in to the front of the driver you'll see what I mean. Acousta-stuf I found works better in this regard.

UV

[Godzilla]

http://www.zillaspeak.com/bib-jordan.asp

I'm drunk... business meeting over... Madeleine Peyroux is singing to me now...

[lousymusician]

Originally posted by uvellani
Did you notice any improvement in the mid-range with the poly batting? If that was what you were after with that. My experience with batting was not very good. I found that it absorbed some of the low freqs and let the upper freqs through. In fact if you take a piece of it and hold in to the front of the driver you'll see what I mean. Acousta-stuf I found works better in this regard.

UV

Didn't try it without. I'm sure the Acousta-stuff is more effective, but for now I'm just using what's in hand.

Now back to the garage to work on the other box...

[Scottmoose]

Originally posted by lousymusician
I didn't mention last night that with the single thickness baffle the FR125 magnet hits the internal baffle. I had to route out a recess for it, stepped from 1/4" to 1/2" deep.

One of the reasons I used to post specific WxD dimensions to ensure that sort of thing didn't happen. And if it did, you had someone else's face to put on the voodoo doll you stick pins in.

Take heed of this warning prospective BIB builders: just make sure what dims you choose allow the driver to fit! Saves so much grief...

Bet they'll still sound good though when they're finished!

[GM]

Originally posted by seanzozo
GM

The height of the mouth that would cause problems WRT large ceilings not the tuning frequency itself. correct? (I know this is correlated directly in the standard BIB to tuning frequency).

If so...

due to the slow flare of the internal board the overall height can be changed by nearly 1 ft by lowering So 6 inches relative to the mouth without changing mouth size.

Whatcha think?

Sean

Greets!

Yes and no since the ceiling extends the virtual horn, lowering Fc and generally smoothing its entire response.

Yes, there are ways to adapt the BIB or short lines (I listed one way many posts ago) to tall ceilings, but these fall into another category and right now we're still trying to do just basic BIBs, or at least I am.

Of course folks are encouraged to come up with their own hybrids and share them with us even if they don't perform well.

GM

[mcgsxr]

Hey lousymusician, how are those FR125's breaking in?

I have a set just sitting on a shelf, that I might see my way clear to boxing up... that design looks interesting!

I think I have sorted out the sizing, having scrubbed this entire thread, but could you clarify that for me?

Total H
Total D
Total W

etc

Thanks!

Almost tempted to try my b200's in one of these... but I really like them in OB, warts and all!

[loninappleton]

Originally posted by mcgsxr
Hey lousymusician, how are those FR125's breaking in?

I have a set just sitting on a shelf, that I might see my way clear to boxing up... that design looks interesting!

I think I have sorted out the sizing, having scrubbed this entire thread, but could you clarify that for me?

Total H
Total D
Total W

etc

Thanks!

Almost tempted to try my b200's in one of these... but I really like them in OB, warts and all!

This is lousyspeakerbuilder ;-)

I had the same problem of figuring out dimensioning but
I had an idea. Maybe someone can program a mini-
calculator to put in the height for instance and spit out
the length and depth.

It's just a guess, but I think Greg and the others want us
to calculate the dims from the area of the terminus (horn mouth)
and length of the fold.


I tried to frame this question earlier but no response at that
time. At this time, I have some edge glued shelving that is
72" x 12" scant. The framing would be 3/4 x 6"x6' poplar
or aspen from the HD glued to the inside dimension of the
edge glued stuff. So 12" scant minus 1.5 in front and back and
3/4 minus for the bottom. The trim of the fold would be cut
(the only cut!) to fit the bottom.


Driver selection from my stock would be FE127e, RS1197
(dims from FE103 are closest I suppose) or way down the
food chain, some 50 cent Pioneer 4 inchers from a line array.


I am working up the nerve to let the crew at HD or someplace
do the panel cuts on some better birch plywood. But I worry
that nothing would come out to a fit.

[giantstairs]

hey lolina,

i'm certainly not one of the experts here but there appears to be very little to calculate. the height is just half the line length of the driver you choose -- 85" (42.5") for the fe103 or 97" (48.5") for the fe126e.

in the fe103 the driver gets mounted 25.5" from the bottom of the speaker (42.5 - 17).

what you have to decide is which combo of width and depth are acceptable to you (and can fit your driver). just make sure the product of the 2 is equal to the Sm.

for example, the fe103 (the dims for less bass) could be 5" x 6.6", or 4.5" x 7.3", etc. for more bass you could use 7" x 7", or 5" x 10", or 6" x 8", etc. just make sure the driver fits. depending on the size of the driver magnet you may need to use a combo of less width and more depth to make sure the piece in the middle allows it to be mounted.

well, this is my understanding at least. i hope others will chime in if i am wrong.

good luck and let us know how it turns out!