Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 526 - diyAudio
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Old 22nd June 2013, 01:01 PM   #5251
Squeak is offline Squeak  Denmark
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Well, it seems to boil down to semantics. High Qts BIBs (which have very different dimensions from low) could very well be said to work more as TLs or waveguides. Vis a vis the drawing from the last page.
I still would venture that a constrained opening/narrowing TL would be a better choice for the driver in question?

Last edited by Squeak; 22nd June 2013 at 01:04 PM.
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Old 22nd June 2013, 01:45 PM   #5252
xrk971 is online now xrk971  United States
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We know Betsy K works well in MLTL - see WIBAQ thread. I was just asking question why we haven't see one in a BIB considering folks have done it with other 8 in full range drivers like the Pioneer BOFU or Visaton BG20, which result in rather large BIB's. But as GM points out, the BIB enclosure is very forgiving and almost any Qts driver will work. The sim with the Betsy does show that it indeed works quite well, albeit the cabinet is huge. I am working on adapting the generalized BIB model to include a definable generalized Karlson aperture based on Aperture length, initial slot gap, and final opening width.
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Old 22nd June 2013, 03:26 PM   #5253
GM is online now GM  United States
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Quote:
Originally Posted by Squeak View Post
Well, it seems to boil down to semantics. High Qts BIBs (which have very different dimensions from low) could very well be said to work more as TLs or waveguides. Vis a vis the drawing from the last page.
I still would venture that a constrained opening/narrowing TL would be a better choice for the driver in question?
True, there's the equivalent electrical-mechanical definitions used to generate the acoustical ones and I prefer to further define them to make it clear as to what type of alignment/shape I'm referring to, but the folks who design using the higher math required can't be bothered, so there's normally much confusion on threads such as this one.

WRT to a TQWT being a better overall loading for high Qt systems, I view it this way……… a reflex with a long vent can be morphed into a TQWT [inverse taped] or truncated by mass loading it [ML-TQWT], so best suited to low Vas and/or low Qt systems whereas high Vas or high Qt systems require big cabs with a big vent area, so can be morphed into a pipe horn [expanding taper] or truncated by mass loading [ML-horn]. The middle range then is best suited to TL/MLTL.

Specific to the Betsy or any ‘FR’ driver for that matter, I’m inclined to always recommend/use either a [ML]TL or [ML]horn since the necessarily highly damped TQWT tends to over-damp the driver’s ability to generate sufficient inner detail beginning in the upper bass/critical lower mids.

Better IME to let the driver ‘sing’ and selectively damp any obnoxious resonances except for those drivers that ‘sing’ really loud and/or low such as some old RadioShack or similar car audio/ceiling PA drivers are wont to do.

In short, guess we’ll have to agree to disagree.

With MJK choosing to call both these expansion extremes the same and unwillingness to change for clarity’s sake combined with Voigt’s, Weems’ and others earlier published inconsistencies, each thread where TLs and/or horns are mentioned is normally a very confusing one, especially for a beginner.

GM
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Old 22nd June 2013, 03:48 PM   #5254
GM is online now GM  United States
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I was just asking question why we haven't see one in a BIB..........
Actually, 'wild burro' did one, though it was done pre-BIB calculator: Enclosure designs for Burro Speakers

Note that the 10:1 TQWT I did was designed for a specific app and only need a MLTL's or MLhorn's low stuffing density, so merely an exception to my general 'rule'.

GM
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Old 22nd August 2013, 01:14 AM   #5255
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https://sites.google.com/site/speake...enclosures/bib

You can download the BIB Calculator from the above link. As I was experimenting with Google Sites I decided to create a project for myself. Everything is under construction so don't expect to find any content.

Zilla
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Old 22nd August 2013, 10:39 AM   #5256
xrk971 is online now xrk971  United States
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Has anyone ever built an in-wall BIB? The 16 in CTC spacing between studs behind drywall will allow you to fit a modified BIB where the top vent would be angled out - use a HVAC grill and it will look like part of the AC vent near the ceiling. The driver would be mounted right at ear level on the drywall. Very high WAF and takes no floor space and good for the media or HT room. Often with the HT room in the basement there is access on the backside of the drywall to put any speaker you want. If you don't have access you can go with a sideways flat BIB or FIB with a smaller driver and fit it in the 3.5 in cavity.
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Old 22nd August 2013, 11:36 AM   #5257
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What a great idea, in-wall BIB! Honey, get my sledge hammer! lol

Larry
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Old 22nd August 2013, 12:06 PM   #5258
xrk971 is online now xrk971  United States
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Originally Posted by larryldspkr View Post
What a great idea, in-wall BIB! Honey, get my sledge hammer! lol

Larry
LOL.

Seriously, a keyhole saw to remove a panel of drywall and build the speaker and replace the panel you just cut with tape and spackling, roll on new paint and you are done! Use construction adhesive to glue the internal divider and bottom and tops (using 1/2 in thick x 3.5 in wide pine board). Cut hole in your rectangular BIB panel that you just cut out for the driver. Add stuffing and wires... She will never even know you did it other than the fact that the driver is on the wall. Now use one of those painted decorator interior speaker grill covers painted to match your wall.
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Old 22nd August 2013, 12:26 PM   #5259
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Originally Posted by xrk971 View Post
modified BIB where the top vent would be angled out - use a HVAC grill and it will look like part of the AC vent near the ceiling.
This angling out would probably negate the effect of final expansion the corners (or ceiling-wall at least) have for the design, turning it into a kind of "hidden transmission line" enclosure. Not bad, per se, but probably without the bass extension that is characteristic of the design.

Gaston
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Old 22nd August 2013, 01:52 PM   #5260
GM is online now GM  United States
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I recall it being discussed a few times, but the low net Vb severely limits driver selection to the point where a high pass is required to protect the driver unless one or more studs are removed. Doing this in a load bearing wall is the best choice, but isn't a good plan unless some additional form of local code approved reinforcement is added.

While most have been sealed, there's been a few MLTLs and TQWTs over the decades, but no longer have any details at this late date.

GM
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