Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 512 - diyAudio
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Old 24th January 2013, 04:50 AM   #5111
GM is offline GM  United States
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Quote:
Originally Posted by xrk971 View Post
I was thinking of slightly curving the divider........
In theory, it should have a 'fuller' bottom end due to the higher compression. I'd just do it as you can always reduce excess gain, which is a lot better than coming up short.

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Old 24th January 2013, 06:00 AM   #5112
xrk971 is online now xrk971  United States
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GM,
I think I will give the curved divider Flatter Is Better (FIB) speaker a try. What do you think of making the divider an inverted "V" (bowed outwards) so that the driver is now centered on the flat panel? There are essentially two horns, half the size now. I guess this would make the lower tuning frequency of the horn higher because the freq is inversely proportional to the mouth circumference?
Xrk
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Old 24th January 2013, 06:09 AM   #5113
GM is offline GM  United States
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Yeah, you would have to make the FIB bigger/longer or run the risk of over-driving it. At this point, doing a proper 'flat' BLH with the terminus at the wall/ceiling juncture seems a better choice overall.

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Old 24th January 2013, 07:07 AM   #5114
hkk is offline hkk  Finland
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Quote:
Originally Posted by xrk971 View Post
GM,
I think I will give the curved divider Flatter Is Better (FIB) speaker a try. What do you think of making the divider an inverted "V" (bowed outwards) so that the driver is now centered on the flat panel? There are essentially two horns, half the size now. I guess this would make the lower tuning frequency of the horn higher because the freq is inversely proportional to the mouth circumference?
Xrk

Hello,
can you make a drawing or scetch of "FIB" so its easier to understand.


Cheers,
hkk
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Old 24th January 2013, 07:24 AM   #5115
xrk971 is online now xrk971  United States
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Default FIB Plan

Flatter is Better Plan for Vifa TC9FD driver. What is not shown are numerous vertical braces every 2 to 3 inches, braces would be aligned parallel to direction of flow (diagonal in the corners). Probably 25 to 30 2 in wide x 4 in tall pieces of 3/16 in thick foam core braces glued with hot melt to back panel and then with PVA to front baffle. Use 90 deg square guide to ensure braces are vertical and square when fastening to back panel with hot melt glue. I would put stuffing in closed end and loosely up the 180 deg turn. Adjust to taste. I think that there may be extensive bass with this design and it may require more stuffing than usual.

Click the image to open in full size.

For those wishing to build this out of wood. You can still use plywood (I would use 1/4 in thick to keep it light so it can be hung on wall). Use the foam core just for the internal diagonal as it is easy to curve by scoring lines on the concave side.

Last edited by xrk971; 24th January 2013 at 07:35 AM.
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Old 24th January 2013, 01:37 PM   #5116
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Hi GM,

Thank you for getting back to me.

Haha, I see what I have done.
The excel Bib calculator that I downloaded had the specs for the old FE206e driver but not the new one.

Boy am I ever glad that I asked before I started cutting wood.
(Measure (check?) twice, cut once)

With one inch build material I now come up with the same ones.
External dimensions of 12*16*76.

At present I have an Cambridge integrated amp and a Sonic T-amp (that I plan to modify) but think that something along the lines of a bottlehead S.E.X. lamp is on the way. Basically, I'll build the speakers and then tailor the amp to them.

So if I interpret what you are saying correctly, the presswood or particleboard is a bad idea for the rear panel and should build it with 1 inch ply to increase the stiffness of the cabinet. If need be, I can adjust damping with felt or stuffing. What about the slant? Optimally, do I want particle board or plywood?

-andre-


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Greets!

Hmm, the only specs I have are the published ones, which = 75.24 H, x 9.982 W x 14.117 D [inside].

45 Hz Fs
2.51 ft^3 Vas
0.1864 Qts

So, what specs are you using?


GM
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Old 24th January 2013, 05:22 PM   #5117
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You can experiment with that speaker by moving it closer / farther from the walls and ceiling. I think it will sound good. Utilizing the room is a great way to get good sound.
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Old 24th January 2013, 05:39 PM   #5118
xrk971 is online now xrk971  United States
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Godzilla,
are you talking about the FIB?
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Old 24th January 2013, 07:53 PM   #5119
Squeak is offline Squeak  Denmark
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xrk971, I know you love your curves, and with the high Qts of the Vifa driver it might work fine, but for drivers with lower values it might not.

You are after all starting with a clearly parabolic horn going into an exponential-ish, it's almost an MLTQWT with a horn on the mouth.

Why not just make a V shaped divider, that would also take care of a lot of the bracing?

Last edited by Squeak; 24th January 2013 at 07:56 PM.
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Old 24th January 2013, 09:18 PM   #5120
xrk971 is online now xrk971  United States
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I thought about the inverted V divider (if that is what you mean by a V shaped divider - good point about bracing), would that not split the mouth into two horns and thereby change the lowest freq the horn can reach due to reduction of the mouth circumference. The curved single divider wall is merely to provide additional clearance for the driver. One option is to make the V divider lower than the top of the box so that the two horns can merge back into one and maybe provide the larger horn mouth?
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