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

[loninappleton]

Originally posted by ilewis33
Hey all -

Here are my heavily modified 126e BIBs, based on the upthread discussions about asymmetrical baffles and measured vs. claimed specs. Lovin' 'em, thanks for all the discussion.

Link to pictures and description

This is a cross post from an unintentional reply:

I dub this the one armed bandit.



Now I am seriously looking at what surgery might be done
to the horn path.

But this is probably giving the regular designers here fits.

[rjbond3rd]

Hi Lon, I think it's cool that ilewis33 worked the problem from both ends (baffle step and line length). Plus he appears to be using several guitars as resonators. It's no longer a BiB of course.

But the BiB is a proven design. It will work! I'm not sure I'd want to shorten the line length because that also has the effect of increasing the distance to the ceiling (so double whammy of higher tuning, less boundary reinforcement).

Glad it worked out for ilewis33 though. It resembles a Bob Brines straight pipe that got folded unevenly:

http://www.geocities.com/rbrines1/Pa...ight_Pipe.html

[loninappleton]

Originally posted by rjbond3rd
Hi Lon, I think it's cool that ilewis33 worked the problem from both ends (baffle step and line length). Plus he appears to be using several guitars as resonators. It's no longer a BiB of course.

But the BiB is a proven design. It will work! I'm not sure I'd want to shorten the line length because that also has the effect of increasing the distance to the ceiling (so double whammy of higher tuning, less boundary reinforcement).

Glad it worked out for ilewis33 though. It resembles a Bob Brines straight pipe that got folded unevenly:

http://www.geocities.com/rbrines1/Pa...ight_Pipe.html

Yes I've seen that one over the years. It's the Noogi's older sibling
and all are children of the Voight Pipe which was used for 8 inchers of various sorts. Means of construction is great because you can get 2 sides out of one sheet and one diagonal cut. I thought about doing these ages ago.

[bigaudioscotto]

Hey Scottmoose
would 60% wool 40% poly batting work
in Saburo's.

Scott

[ilewis33]

Originally posted by rjbond3rd
Hi Lon, I think it's cool that ilewis33 worked the problem from both ends (baffle step and line length). Plus he appears to be using several guitars as resonators. It's no longer a BiB of course.

But the BiB is a proven design. It will work! I'm not sure I'd want to shorten the line length because that also has the effect of increasing the distance to the ceiling (so double whammy of higher tuning, less boundary reinforcement).

Glad it worked out for ilewis33 though. It resembles a Bob Brines straight pipe that got folded unevenly:

http://www.geocities.com/rbrines1/Pa...ight_Pipe.html

Ha! Yeah, if I put my electric guitar amp in that corner and turn it up, you can indeed hit a chord, mute it, and hear the acoustic guitars on the wall ringing in sympathy... pretty cool.

My BIBs started out life normally:



However, after reading that the 126e Fs measured out at 90 Hz as opposed to 70 Hz, I made the decision to cut the line length down to match. It really did tighten up the bass, and I have a sub with crossover point set at about 80 Hz, very low gain. Since the 4.5 inch driver BIBs are so short , I don't think it was doing much ceiling loading anyway.

I like the one-armed bandit description. I just need to clean them up a bit, as they look incredibly "agricultural" now. I recently moved them into my sunroom, where there are no obstructions between the speakers, and wow, that really does make a huge difference in the soundstage.

I've been thinking of different folding patterns - a BIB is basically just a folded linear expansion horn/resonator, right? I thought one which had the horn mouth pointing straight back at the wall, on the floor, would be neat. Just trying to stay in the spirit of as few cuts and pieces of wood as possible.

[Scottmoose]

Would 60% wool 40% poly batting work
in Saburo's.

Should do.

These measurements of a pair of BIBs were posted here some time back, but I can't for the life of me remember who did them, or exactly where. Sorry about that. But I thought it would be a good idea to have them up again as a reference. Illustrates the point that they are intended as corner horns, as well as roughly the kind of response you can expect.

[moray james]

to those who attempt to do damping with felt. There is no substitute for real wool felt. Synthetic felts and blends of synthetic with wool are not the same thing. Wool is wool and it comes from a sheep or a goat.

[GM]

Originally posted by ilewis33

Since the 4.5 inch driver BIBs are so short , I don't think it was doing much ceiling loading anyway.

I've been thinking of different folding patterns - a BIB is basically just a folded linear expansion horn/resonator, right? I thought one which had the horn mouth pointing straight back at the wall, on the floor, would be neat.

Herein lies the crux of the matter in that the driver's 'Fs' has no real bearing on its performance if proper corner loading is achieved until its 'Flm' cut-off is reached, which for most drivers used in BIBs will be down in the <10 Hz BW which will normally put it below the room's first mode, so within reason the driver will be somewhat protected to below audibility and with a useful BW to well below its 'Fs'.

AFAIK. Anyway, buried in this thread I discuss the fact that the few 'BIBs' I built were all floor corner loaded to get the max gain BW like an early day corner BLH by simply adjusting the pipe's distance from the corner since I didn't know the math to work it out empirically, though to do it right you have to use triangular shaped cabs. Still, decent corner loading can be achieved by just cutting off a narrow cab's lower back at an angle since you're trying to load the corner's apex as much as practical.

GM

[loninappleton]

No more cutting on the builds.




I just got one stood up.

[pkcain]

Hi everyone,

This is an awesome thread with a TON of info... thanks!
I have a question that doesn't seem to have been asked yet. What about the Hemp FR6.5c driver? I used GM's calculator and came up with this:

Fr=50.0
Vas= 45.30 liters (!)
Qts = 0.44
LL = 134.65
Zdriver = 29,22
Sm = 294.29(!!)
W = 14,43
D = 20.40
H = 67.32

I am surprised by the Sm... it's the same as what I've heard for the FR8 driver. I've also seen mention of an Sm of 200 and it seems to have worked for the FR8. Does anyone have any experience with this driver or suggestions on how I could get this a bit smaller? I like the idea of the Hemp drivers but maybe my size (wife?) limit will put me closer to the 168 Sigmas.

Thanks!