Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks?

My Layout

Here is the layout of the BIB I completed! I hope it helps someone. I also purchased Nagaoka Tetsuo's Mook Book #5 & it has many designs for the Fostex drivers, Folded Horn, Acoustic Suspension and Bass Reflex Designs. Detailed cabinet drawings and numerous photos are included. I got it at Madisound.com.
 

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diyAudio Editor
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BIG BIB BEMERGENCY!!

My buddy suddenly has time tomorrow to make a BIB. This is unusual for him and he has a huge table saw, so I need to seize the moment!

I checked the thread the best I can and it seems that no one has actually made a BIB with the Pioneer B20FU20-51FW

From the website:

http://www.zillaspeak.com/bib-pioneer.asp

I come up with
L(line Length)= 138"
Sm(inside dims of box) = 200sq in
So(driver distance from the narrowest point, ie interior top)= 30" down.

That makes the center of the driver 3'-7 3/4" off the floor, which means that I can make the So longer (ie driver closer to the floor) if that helps. I know that that length sometimes the So of the design has been adjusted sometimes to a less optimal position to ensure that the drivers are the right dimension off the floor, so if in fact making it longer is optimal, than I could do it. If making it shorter is optimal, thaen I guess I'll leave it as it is...


Also if the height of the whole thing should be a bit higher (affecting the "L" , then that also could be adjusted up to say 4 inches taller, as there is a bit of extra wood.

Also, what happens if I make the Sm 190 sq in instead of 200? Are the calcs that accurate? or is 5% smaller not so important? I could save an entire sheet of ply if I do that and this is a prototype for having a "Speaker Building Workshop" in about a month for 6 teenage potential audiophiles.

Could you guys give me quick feedback on these issues?

It's an emergency...


Thanks
 
Making the Sd 190 instead of 200 should be quite marginal in my opinion, probably less than one dB in the 50-100 Hz range.

Moving the speaker up or down may however have quite significant impacts. It should not be done without doing some simulations.

Best of luck with your woodwork Variac :)

SveinB
 
Variac said:
BIG BIB BEMERGENCY!!

My buddy suddenly has time tomorrow to make a BIB. This is unusual for him and he has a huge table saw, so I need to seize the moment!

I checked the thread the best I can and it seems that no one has actually made a BIB with the Pioneer B20FU20-51FW

From the website:

http://www.zillaspeak.com/bib-pioneer.asp

I come up with
L(line Length)= 138"
Sm(inside dims of box) = 200sq in
So(driver distance from the narrowest point, ie interior top)= 30" down.

That makes the center of the driver 3'-7 3/4" off the floor, which means that I can make the So longer (ie driver closer to the floor) if that helps. I know that that length sometimes the So of the design has been adjusted sometimes to a less optimal position to ensure that the drivers are the right dimension off the floor, so if in fact making it longer is optimal, than I could do it. If making it shorter is optimal, thaen I guess I'll leave it as it is...


Also if the height of the whole thing should be a bit higher (affecting the "L" , then that also could be adjusted up to say 4 inches taller, as there is a bit of extra wood.

Also, what happens if I make the Sm 190 sq in instead of 200? Are the calcs that accurate? or is 5% smaller not so important? I could save an entire sheet of ply if I do that and this is a prototype for having a "Speaker Building Workshop" in about a month for 6 teenage potential audiophiles.

Could you guys give me quick feedback on these issues?

It's an emergency...


Thanks


I would be very interested in your build and quality of sound.

gychang
 
Re: My Layout

ForestGump72 said:
Here is the layout of the BIB I completed!

Interesting, I don't have the book, so is the right side triangular space unused? If true, then this would technically be a BVR style BLH rather than a BIB. If the plan is designed 'close enough' to your driver's specs it should easily out perform a BIB overall. Regardless, thanks for sharing!
 
A couple of questions........

Interesting, I don't have the book, so is the right side triangular space unused? If true, then this would technically be a BVR style BLH rather than a BIB. If the plan is designed 'close enough' to your driver's specs it should easily out perform a BIB overall. Regardless, thanks for sharing!

Please explain why.....& what's BVR?

Does the small opening only allow lower frequencies to escape?

Would you then stuff the top & line the back & the bottom?

Would you use the same basic measurements as for a BiB or does the box-like inclosure need to be bigger?

Would this design eliminate the need for a close ceiling / corner?

Which measurement of a Fostex Full-Range becomes the most importent consideration?

Could someone walk me through the method of using a PC based sound card and a downloaded program to get these audio measurerments / charts you guys use?
Thanks....
 
Re: A couple of questions........

edgebc said:
Could someone walk me through the method of using a PC based sound card and a downloaded program to get these audio measurerments / charts you guys use?
Thanks....

A good idea. I have not seen many measurements in the BIB thread. (I will try to post some measurements of my FF165K BIB soon).


For measurement I recommend you download ARTA
The [free] demo version is fully functional, only lacking the possibility to save compleate measurement files to disk.
Using a PC with built-in soundcard and a microphone you can start practicing today!

Then you need a decent microphone.
The virtually no cost solution is a Panasonic WM-61A electret capsule at $2 a piece. The mic needs a battery and a couple of resistors for power feeding, as described here: Powering Microphones

There are also a few threads on this subject in the Loudspeaker section (search for ARTA).

SveinB.
 
re some of the above questions:

The BIB has linear expansion, so deviating means it's no longer the same thing. That doesn't mean its bad, just that you've done something different.

The narrow gap near the base will act as a filter, as in a regular BLH, restricting the passband of cabinet operation. What you've got here is a very large, tapered back-chamber (the first half), coupled to a horn vent (the 2nd half), so you have a blend of reflex & some horn action (view it as a BR box with a horn loaded vent). No bad thing, albeit arguably the diametic opposite of a pipe horn like the BIB. Yes, it probably would eliminate the need for wall / corner positioning as they're not needed to continue a horn expansion given that we've now simply got a reflex box with a massive vent. As for whether it'd need to be the same size -who knows? They're completely different in design terms & would be better off being designed with this in mind. A BVR is best done as a regular reflex alignment, and the vents then proportioned for optimal end correction / loading / whatever the design goal happens to be. It probably won't need much damping as little in the way of HF is going to get through. Again, best to treat it as a reflex box, get some material behind the driver to prevent reflections back through the cone, and then some lining at strategic points.
 
Hi all.

Thanks to everyone especially scott, HM, Godzilla and many others who has contributed and published this design for us all.

I am in the process of building a 206Fe BiB with a ft17H super tweeter.
From Godzilla's site (which is a challenge to access ;) ) I have decided to pick out the short version to build.

Dimensions in from Godzilla site.

L=140"
Sm=133.875"2
Zd = 28.5"

The Zd listed is a bit shorter from the guildline (140*0.217 = 30.38). should i stick with the guildline of 30.38" Zd and place the supertweeter at the bottom of the mid/bass driver?
 
I am also interested in making a pair of Monacor SPH-60x BIBs. I've bought the drivers but just wanted to check the dimensions that people have been using - have people just taken Scottmoose's figures from the Zillaspeak site?

A further question I have is has anyone modified these drivers? I know that various mods such as painting puzzlecoat etc on the cone and adding a phase plug have been tried successfully on the fostex drivers - but haven't found any info about the monacors. Would it be better to leave well alone and save for better drivers?
Cheers,
Jon