I'm just catching up on the last week or so, and I see that GM has put forth an easy way to design a BIB. Just so I've got my head around it, here's what I've gotten from it, correct me if I'm wrong:
(variable names refer to those in this diagram, I've also added some annotations.)
Inputs:
Outputs:
Tom.
(variable names refer to those in this diagram, I've also added some annotations.)
Inputs:
- Fs (tuning frequency of BIB)
- Vas
- Qts
Outputs:
- formula: L = (13464.54(SpeedOfSound in inches/second))/2(half wave) /Fs (tuning Freq)
- formula: H = L/2 (folded)
- formula: Vb = 20*Vas*(Qts^1.25)
- formula: Sm = Vb(in ft^3)*(12^3 (inches in ft^3))/L (should be H?)
- formula: D = (Sm * (2^.5))^.5(pseudo golden ratio?)
- formula: W = Sm/D
- formula: Zd(So?) = L * 0.217 (fudge factor?)
- formula: a,b,c = D/2
Tom.
Re: Bib tweak update attn: GM
Greets!
Seems to me that this type of felt would be far too restrictive to work well. I mean can you breathe through it?
GM
loninappleton said:
Greets!
Seems to me that this type of felt would be far too restrictive to work well. I mean can you breathe through it?
GM
renfrow said:
Greets!
Yes, should be 'H'.
Not really, though it's a very good acoustic ratio also, but it was chosen due to it ~preserving the expansion through the bend.
No, it's the driver off-set from the closed end chosen for a good balance between flattest response and max gain BW.
GM
Re: Re: Bib tweak update attn: GM
I can't breathe through foam padding either. That's what's in there now but not cut to the right size. 'Don't know what some gauzy stuff in there would do.
As to shape, depending on the orientation, the bottom part can be
pretty much parallel to the top or if hung crosswise would be tapered.
The goal is to control boominess. I'm trying to get my ears working to identify what it is I should be hearing out of the top.
In normal listening position, the foam thingy has provided some benefit. The only interior treatments are a square of stuffing at the base and a bit up in the closed end peak.
Perhaps use the felt along the divider (as others have done) or hung loose at the rear?
GM said:
I can't breathe through foam padding either. That's what's in there now but not cut to the right size. 'Don't know what some gauzy stuff in there would do.
As to shape, depending on the orientation, the bottom part can be
pretty much parallel to the top or if hung crosswise would be tapered.
The goal is to control boominess. I'm trying to get my ears working to identify what it is I should be hearing out of the top.
In normal listening position, the foam thingy has provided some benefit. The only interior treatments are a square of stuffing at the base and a bit up in the closed end peak.
Perhaps use the felt along the divider (as others have done) or hung loose at the rear?
Greets!
If I can't breathe through it (or blow very low pressure air through it if fiberglass or similar), then I don't use it in a cab for reducing reflective energy. To control 'boom', the traditional method was to stretch a membrane across the vent or mouth and one reason why speakers, BLH horns were 'voiced' with very taut, close fitting grill cloths, sometimes even multi-layered.
GM
If I can't breathe through it (or blow very low pressure air through it if fiberglass or similar), then I don't use it in a cab for reducing reflective energy. To control 'boom', the traditional method was to stretch a membrane across the vent or mouth and one reason why speakers, BLH horns were 'voiced' with very taut, close fitting grill cloths, sometimes even multi-layered.
GM
interruption-- where do the wires exit?
Sorry for the interruption folks, but a newbie question: where do the wires in a BIB exit? Do I drill small holes in the rear panel? Through the bottom?
Thanks,
Andre
Sorry for the interruption folks, but a newbie question: where do the wires in a BIB exit? Do I drill small holes in the rear panel? Through the bottom?
Thanks,
Andre
Re: interruption-- where do the wires exit?
I'll do the same with mine.
yea why not!?drec said:
I'll do the same with mine.
Im sure its somewhere in these 299 pages, but how do I get from the line length and mouth areas given on Godzilla's site to actual interior dimensions? Height and interior divider length in particular.
L = (Line length) 136in
Zdriver = Driver 27.5" down from sealed end of cabinet
Sm = 87.75in^2
Will likely be using 3/4" wood. Driver is Fostex FE166 ES-R.
L = (Line length) 136in
Zdriver = Driver 27.5" down from sealed end of cabinet
Sm = 87.75in^2
Will likely be using 3/4" wood. Driver is Fostex FE166 ES-R.
This BIB cab calculator has the cab height =(depth+length)/2 which confuses me as earlier calcs, and the one I used to build my 168 BIB, simply have length/2.
Has something changed? I don't understand why you would add the cab depth to the line length??
Chris
Has something changed? I don't understand why you would add the cab depth to the line length??
Chris
Quite easy, if you think about it for a sec...
The sound travels HORIZONTALLY at the bottom....
If you take the center of the line, the horizontal distance is HALF of the 'depth'...
See the red line here: http://www.zillaspeak.com/bib-howtobuild.asp
Cheers, Paul
The sound travels HORIZONTALLY at the bottom....
If you take the center of the line, the horizontal distance is HALF of the 'depth'...
See the red line here: http://www.zillaspeak.com/bib-howtobuild.asp
Cheers, Paul
Yes, but the red line path does not go to the bottom of the cab so this is already taken into account surely?
What I mean is that the path in that diagram represents the full length of the line without having to add anything for the cab depth. In fact its the horizontal section of the path that increases the length and compensates for the fact that the line does not go to the bottom of the cab.
One question about the cab construction:
Do I need to leave the base removable?
For damping or whatever?
Some use felt, some not, what to do?! 😕
Do I need to leave the base removable?
For damping or whatever?
Some use felt, some not, what to do?! 😕
bibster said:
Greets!
FWIW, when I DL this it's only a 3.95 kB 'something' that Winzip says is empty and Excel, etc. only displays as either a bunch of programming or says it's in an unrecognizable format.
GM
ChrisMmm said:
Greets!
I've repeatedly posted that if you use a SQRT(2) 'Sm' width:depth ratio, then dividing L/2 preserves 'close enough' the area expansion through the bend AFAIK, so no need to add any depth to it as Dave's calculator does or any internal baffle thickness as others keep saying. AFAIK no one has shown me where I'm wrong, so that's my 'story' and I'm sticking to it. 😉 Once you move away from this ratio though, for best accuracy you have to figure out how the expansion changes and any impact it has on the acoustic path-length (L).
Regardless, IIRC Scott used MJK's more advanced WS that plots the expansion through bends to sim the original BIB, mine, and some other combos and they were all acoustically close enough that I doubt the differences would be audible in-room unless the ratio deviates too far from the ~ideal.
As always though, YMMV.
GM
resident said:
Greets!
If you don't have a way to install/remove damping material till you find what sounds best to you, then a removable side or bottom seems mandatory in the case of a pipe horn. I never used felt in them other than on the driver or any stuffing in the bend IIRC, instead dealing with any excessive reflections/'boom' with damping at the throat and/or at the mouth. Parallel wall reflections were dealt with by selective damping around the driver and by various means/materials as required, so the bottom line is that it's too subjective for anyone to arbitrarily spec what material(s)/quantity is to be used where inside BIBs for all systems.
GM