Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 408 - diyAudio
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Old 2nd June 2008, 01:01 AM   #4071
diyAudio Member
Join Date: Feb 2004
Location: Appleton, WI
Originally posted by GM

Not sure I completely follow especially WRT to the double baffle Vs 'extra piece', whatever it is.

If by 'extra depth' you're referring to the driver being mounted on a double thickness baffle, then as long as this 'tunnel' is expanding at least at a 90 deg included angle (which can be 'stepped', i.e. internal hole diameter is larger by at least 1.5" if 0.75" thick), it should actually be closer to the sim since this extra volume should ~offset the loss in the tight confines of the pipe horn due to the driver's bulk.

The only extra piece would be the double baffle. I cut extra pieces in case I don't hit the mark for a hole cut out or some other snafu occurs.

This particle board is under 3/4 depth. Doubling up will not be as deep as normal particle board or ply. It's maybe 5/8 for shelving.

If I do this, I will measure off of one, center the pilot hole and do one piece with 4 in hole saw and one with a 5 in.

I've done this and chamfered for the Harvey. Also tried it in combination with a jimmy-rigged supra baffle on the GM MLTL.

I do not know if my plan to have a flush mount jig will happen all of a piece with this particular build. If I have to free hand another one, hey, at least I'm getting practice.
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Old 2nd June 2008, 11:07 AM   #4072
zBuff is offline zBuff  New Zealand
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Join Date: Nov 2004
Location: NZ
Default Non parallel side walls?

Has anyone tried making a BiB with non parallel side walls? I was thinking of trapezoidal shape if view from the top, flare out to the back, looking from the front.

I figure it would change the expansion rate assuming you didn't reposition the internal baffle. It take away one of the best things about the BiB, the ease of build, especially the internal baffle would be alot harder to measure and cut. But are there any advantages to be gained?

Also can anyone think of a way to magnet mount a driver in a BiB?
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Old 2nd June 2008, 04:14 PM   #4073
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Location: New York
I bought piano hinges today and will set up a wing later this week. I am looking forward to critical listening. If it sounds good i will let you know. One BIB will have a wing one will not.

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Old 2nd June 2008, 06:57 PM   #4074
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Join Date: May 2005
Location: Buenos Aires
Originally posted by Godzilla
I bought piano hinges today and will set up a wing later this week. I am looking forward to critical listening. If it sounds good i will let you know. One BIB will have a wing one will not.

That's great !
I hope you like the results.

If you want to do a coarse test, this would be the results (front baffle contribution only) with just a wood strip sitting to a side of the BIB. A wide front baffle with a non-symmetrical location for the driver.

Click the image to open in full size.

Click the image to open in full size.

Notice the additional ripple between 500Hz (highest peak) and 2KHz. Almost 2dB. Not annoying IMO, but in this case, bigger is not necessarily better. It will let you feel the change in the midbass without need of drilling or cutting, at the expense of changes in the most sensitive area of our hearing.
I wouldn't implement this full baffle when a better approach is visually more appealing too, but that's just me.

The front baffle of my BIB, that was as a whole calculated with the calculators to be found in your site (http://www.zillaspeak.com/bib-howtobuild.asp) are:

*external* height: 178cm = 70.08"
*external* width: 26cm = 10.24"

The full wing (no shaping) is 23cm = 9.06" width.

The "optimized" wing in this case starts at
and end at y=166cm=65.35" on the BIB side.
The farthest (shortest) side of the wing starts at y=40cm=15.75"
and ends at y=150cm=59.06".

Feel free to publish all of this information. I think that a mention to "The Edge" would be a nice touch, as it is what I used for the analysis. But first let's let your ears decide if it's worth

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Old 2nd June 2008, 08:58 PM   #4075
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Join Date: Apr 2008
So I'm considering making a pair of BiB's, using some canadian speakers ( McBride's from http://www.loudspeakers.ca/ ), but I'm concerned that they don't list the full T/S parameters, or even have a SPL-vs-frequency graph available (I already asked)...

So is this enough info to build a BiB? Will I be able to measure the T/S parameters directly?


8” foam edge
dual cone fullrange

Outside Dia...........................208 mm
Impedance...............................8 ohm
Power ........................................30 W
Freq. Resp ................40 Hz - 18 KHz
Magnet Wt ................................10 oz
Fs .............................................40 Hz
Voice Coil Dia .........................25 mm
SPL...........................................92 db
Depth ......................................82 mm
Baffle Opening......................183 mm
Mtg. Cntr...................195 mm BC x 8

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Old 2nd June 2008, 10:09 PM   #4076
GM is offline GM  United States
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Location: Chamblee, Ga.
Not with any degree of accuracy. Yes, you can measure its specs. Anyway, tiny motor = high Qts, maybe as high as 2.5, so better IMO to try the MCWR8A, which has a motor size in line with its published T/S specs and add an inexpensive super tweeter if required.

Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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Old 3rd June 2008, 01:43 AM   #4077
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Location: New York
I tried adding a few different sized wings today. There is a definite change in the sound. I hear added weight to vocals (i spent about 30 minutes listening to a Squeeze CD with and without wings). Vocals are fuller, especially on multi singer harmonies. I liked the change but have to decide what size wings to make. My BIB uses the 165k driver so it is in the 165, 166, 167 family of Fostex drivers. To me, the best sounding wing was about 6 inches wide by about 60 inches tall as compared to a wing 11 inches wide by 30 inches tall. I may split the difference and make some cosmetic alterations ending up with a wing 7 inches by 42 inches and call it a day. This way i can enjoy the improved sonics as well as enjoy this unique wing feature. I may play around with more sizes but am convinced for now this will only make the BIB even better. I have no measurement tools, just my ears. But i did like what i heard. If you think vocals sound thin on your BIBs this is a tweak to play around with.

Very cool,
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Old 3rd June 2008, 02:01 AM   #4078
tilroh is offline tilroh  Australia
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Godzilla, do you have the wings on both sides on the boxes or just one?
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Old 3rd June 2008, 02:28 AM   #4079
gnugear is offline gnugear  United States
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I noticed the same added weight when I added a BSC. I like the fullness and I'm sure the "wings" are doing the same effect.
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Old 3rd June 2008, 03:28 AM   #4080
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Join Date: Aug 2006
Yeah, but they are doing it without adding anything inline with the signal/source . This has to do with wave propagation off the baffle, and is IMO a MUCH better alternative to a BSC circuit , being closer to a cure rather than a quick fix.

Wide baffles rule.

Keep it simple
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