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pjanda1 11th August 2012 10:46 PM

BIB dimensions
I've been getting quite a few questions about BIB dimensions for the BetsyK. As I said in the "enclosures" forum, these are the dims I used:

L = (Line length) 150.5"
Zdriver = Driver 30.1" down from sealed end of cabinet
Sm = 200"^2

They are a good bit smaller than GM's formula would give you, but they had more than enough bass in my room. I wish I could remember what my exact dimensions were, but I think I used something like 11.5x17.4 WxD internal open space, which means my actual enclosures where 13" wide x 20.4" deep or so. (I used a double thickness front baffle. If you don't, you only need to add three thicknesses to get to your exterior depth). I can't remember how tall they were, but I do know that after trying to accurately calculate the height including a changing radius around the bend, it ended up being really darn close to just assuming straight lines.

hopefully that helps!

Wild Burro Audio Labs - DIY Full Range Speakers

opa1 11th August 2012 11:46 PM

Thanks for the thread. Trying to read through 5053 posts on the TC bib thread will give you a Somewhere in the posts GM figured out how to sim the bibs. There is a chart for alot of drivers posted. I couldn't find a sim on the Betsy K. It seems that the design is very forgiving. Using your measurements. The height would about 78". So a internal of 12" wide and depth of 18" and 78" tall. Thats with a single 3/4" baffle. Not sure how for from the bottom to terminate the the internal piece. Placement front to back is unknown too. It could start at the top and go down to about 9" from bottom. Then center it at 9" from the back.[guessing] It would vent out the top. Maybe someone will chime in with there build.

pjanda1 12th August 2012 01:07 AM

Many people seem to have the bottom of the baffle equidistant from the front, bottom, and back. A more constant rate of expansion makes sense to me. Here again, I can't recall what I did. But it would have been something like half-an-inch closer to the front than to the bottom, and half an inch closer to the bottom than to the back.

Notice that with these specs, the speaker ends up pretty high. They'd be a little more difficult to deal with, but you can consider building an inverted BIB to get the driver right at ear height.


opa1 12th August 2012 01:22 AM

The driver would be about 48" up from bottom. I see what you mean.

pjanda1 12th August 2012 01:28 AM

I didn't mind the driver height, but I didn't love it either. I mention it now, as if you are going to consider inverting, it would be good to have that in mind from the beginning. There are also potential loading advantages. If you have the vents loaded with the floor, you might be able to get the speakers out from the wall a bit, which could have positive effects on imaging.

Wild Burro Audio Labs - DIY Full Range Speakers

opa1 12th August 2012 01:43 AM

It could be floor/side bottom vented too. I'll have to do some searching and figure the port size.

GM 12th August 2012 05:08 PM

opa1 12th August 2012 06:44 PM

GM is quick!!

opa1 12th August 2012 07:46 PM

Speaker specs.
L=13526.5/2/49.95 L=135.400
H=L/2 H=67.7
Vb=20*Vas*(Qts^1.25) Vb=624.692
Sl=Vb(in ft^3)*(12^3(inches in ft^3))H Sl=109.522
D=(Sl*(2^.5))^.5 D=12.4470
W=Sl/D W=8.801
Zd=l*0.217 Zd=29.381
I think my cal. on the Sl is wrong. A cab of 67.7x12.44x8.801 doesnt seem right. Where did I go wrong?

GM 12th August 2012 08:08 PM


Originally Posted by opa1 (
GM is quick!!

I recorded them when done for a quick reference. ;)


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