Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 358 - diyAudio
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Old 2nd October 2007, 12:27 AM   #3571
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Quote:
Originally posted by resident
Isn't this a nice emmmm, BIB?
Or not?
No, a larger, upside down BeauHorn B2. A shame they are hiding all the curves with those big side panels.

Click the image to open in full size.

Click the image to open in full size.

dave
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Old 2nd October 2007, 03:48 PM   #3572
stroop is offline stroop  Germany
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Hi Folks,

That looks like it could be converted into a much simpler build, like a bib. But with the chamber added. No longer tapped I know, but surely there could still be a very long pipe using the ceiling like the BIB does.

What do you think?

Stroop
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Old 4th October 2007, 11:05 AM   #3573
germpod is offline germpod  United States
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Any ideas on how close to the ceiling the top of the enclosure can get without negative effects? Some BIB's are 7' tall and I only have 8' ceilings, so just wondering how much I would have to shorten the height.

Thanks

Ed Robinson
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Old 4th October 2007, 01:31 PM   #3574
GM is offline GM  United States
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Quote:
Originally posted by stroop

That looks like it could be converted into a much simpler build, like a bib.
Greets!

Works for me!

GM
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Old 4th October 2007, 01:55 PM   #3575
GM is offline GM  United States
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Quote:
Originally posted by germpod
Any ideas on how close to the ceiling the top of the enclosure can get without negative effects?
Greets!

Well, the closer to the ceiling it is, the greater the slot loading, so from this POV it would have to be very close indeed to be too close. If you mean to keep it from being slot loaded, then at minimum it has to be beyond the pipe's acoustic length at whatever the driver's max low distortion excursion is, so no set distance.

BIBs typically have a large enough terminus and use low enough suspension limited (Xsus) drivers though that a pipe's end correction formula is probably sufficient, so calc the mouth's effective radius, then Dmin = > radius*0.613 and > 3*radius if you want no doubt.

GM
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Old 4th October 2007, 03:17 PM   #3576
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Quote:
Originally posted by GM
BIBs typically have a large enough terminus and use low enough suspension limited (Xsus) drivers though that a pipe's end correction formula is probably sufficient, so calc the mouth's effective radius, then Dmin = > radius*0.613 and > 3*radius if you want no doubt.
Hi GM... I assume the effective radius of the mouth would be the radius of a circle whose surface is equal to the effective one of the mouth of the BIB. If so, then

eff radius = sqrt( D x W / pi )

now... why 0.613 ?

Greets

Gastón
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Old 4th October 2007, 03:30 PM   #3577
RKH is offline RKH  United States
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Quote:
Originally posted by ghpicard


Hi GM... I assume the effective radius of the mouth would be the radius of a circle whose surface is equal to the effective one of the mouth of the BIB. If so, then

eff radius = sqrt( D x W / pi )

now... why 0.613 ?

Greets

Gastón

The 0.3*diameter or 0.6* radius is the 'standard' end correction for open tube resonance. You can find an introductory discussion here


http://physicsforums.com/archive/ind.../t-166445.html

RKH
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Old 4th October 2007, 09:48 PM   #3578
stroop is offline stroop  Germany
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Hi GM!

Where would you start with something like that?! A compression chamber with a BIB.

I know this is over simplistic to the max or maybe just a dumb question... but does the size of the compression chamber remain the same for a specific driver and just the line length changes according to how low you want to go or does it all work in together....

For the fe168e sigma in a bib, line length is around 132 inches, with an Sm of around 81 sq inches. Zdriver at 28 inches for end. I understand that a BIB is a tapped horn. So I presume that I can't just stick a compression chamber on the end of this and expect it to work!

I think this could get real tricky...

What improvement could be expected if any, with compression chamber as opposed to the BIB.

It just seems it could be only mildly more difficult than a BIB to build!

Cheers Stroop
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Old 4th October 2007, 10:19 PM   #3579
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It's a filter chamber, not a compression chamber. For a BLH, the room is the CC. The filter chamber simply determines the upper cut-off frequency of the horn. There are lots of ways to determine it's volume, Leach's, Keele's etc., and frankly the pre T/S alignments such as V=2.9R*At generally work as well as anything else.

In terms of benefit, it will mean the cabinet will roll off at a specific point (more or less) rather than not having a limit, the upper frequencies being damped out by the bend and stuffing / lining. Downside, they're a little more complicated to build & get working right.
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Old 4th October 2007, 10:39 PM   #3580
stroop is offline stroop  Germany
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Hi Scott!

Oooops er yeah thats what I meant!!! Filter chamber...filter chamber...filter...

Scott that's really cool! But I'm an idiot and have no idea what that equation translates to! I know you don't have time explain either and thats ok!!!!!

Pretty tricky to work out then.

Would it be a simple case of taking an existing horn enclosure that works and then straightening it out to fire to the ceiling....I know its cheating...but as a starting point? er... provided it is not one of the exponential types which would then be also tricky to build.

Cheers Stroop
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