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

Hi Scott,

Forgive me, a bit OT here.. I'd try your suggestion re: enlarging driver hole for OB at extra panel behind main baffle. It would be harder since I can't remove the rear extra smaller panel (already coupled with glue n screws) of the largish baffle. But I'm curious to hear the difference. Thanks.:)
 
Nowhere until they're in position and you know what they're doing! This is one case where you really do have to stuff-to-room. I know that sounds like a cop-out, but since these use the room heavily, there's no real way of knowing beforehand. If things boom too much, try lining the second side of the sloping baffle wall (the bit that goes up to the terminus). That often works well.

Cheers
Scott
 
Re: this weekend.

blumenco said:
...........are we really even after this level of refinement, or should we even be? at what point is it more economical to build true folded horns?

Greets!

Not really, the BIB is just a simple box design to get enough gain to allow LF/midbass challenged drivers to play low without much hassle, complexity, or cost, with the major trade-off being size, so it was made tall to minimize its footprint as much as acoustically practical. Once you start tweaking it much, it's best to start from scratch with each driver.

GM
 
Re: this weekend.

Scottmoose said:
I'd be very grateful if you could still send Jeff & myself a copy of your own sheet that you mention though Greg... I tried coming up with something in Excel myself month or so back, but I'm lousy with spreadsheets unfortunately.

Regards
Scott

Greets!

I started writing an instruction sheet and decided it would be as confusing as the WS, so began reworking it instead, but keep getting side-tracked for one reason or another.

GM
 
Re: this weekend.

Dave Cigna said:


GM, could you elaborate little? Do you mean something other than the linear taper of a typical TQWT?

Greets!

No, in any resonant pipe regardless of taper there's an acoustic point where the driver's and pipe's resonances balance out for smoothest combined output and as it tapers from constant (straight) it moves in the direction of the taper from this point, ergo in a TQWT (reverse taper) it moves towards the closed end and for a horn (positive taper) it moves towards the mouth.

GM
 
Re: Re: this weekend.

RtV said:
I am planning to go forward by mounting the driver into a 1" disk (like a Terry Cain cabinet) halo'ing the driver, and giving enough space for the magnet internally.

My question for the theory gurus: could this have an effect on any other dimension of the design?

Greets!

Theory and reality come together with the conclusion that as long as the 'tunnel' isn't too deep and the walls flare away at a sufficient rate to keep reflections from audibly modulating the diaphragm, then it's not an issue. Typically this means a > 20 deg chamfer and < ~3.4" deep.

GM
 
GM said:

Theory and reality come together with the conclusion that as long as the 'tunnel' isn't too deep and the walls flare away at a sufficient rate to keep reflections from audibly modulating the diaphragm, then it's not an issue. Typically this means a > 20 deg chamfer and < ~3.4" deep.

This is great info! Without much experience in the matter I was going ahead by adding 1" of depth and routing out a 45 deg chamfer. Now I can do it with a little more confidence. Much thanks.

Randy
 
they are done.

well, they have been assembled and playing for a week or so. the results have been very very good. astounding, in fact.

the bass is great and all, but I am hearing all kinds of weird unexpected magic in the midrange as well that I did not know this driver capable of posessing. I suspect that the voight half of this pipe really helps here. the side panels the other. the only metal in the things is the t-nuts and hex bolts. there is a tiny bit of wool felt on the front side of the magnet. no other damping material and they sound perfect, more or less.

there are really alot of factors going on here. the wood is nice. I also sealed the driver to the cabinet with a little adhesive neoprene foam strip. bass is typical of a good horn. lots of speed. lots of impact. very instrumental. they are really amazingly clean and disgustingly accurate for how undamped they are. I really really like that. horns are supposed to be horns - straight up-. no monkey business. the goal is reinforcement. not filtering. just my opinion though...

the bases are double thick ply, and pretty wide for stability. the false baffles on the sides are cool sounding. a little ugly for now, just proportionally. I am considering cutting them in half, creating a little triangular box with what is left on the cabinet, and filling it with sand. hopefully extra power of bass, and even fewer resonances, while still a little of that nice wave launch thing. however, these things sound so clean, that the resonances are quite desirable - life. the plywood used was white maple 3/4 from home depot. it cost a pretty penny, but the results are good so eh what the hey.

It came to my attention that there is better lumber cheaper in town so for my next project I will go there.

the bass is very good as I suspected. there is the recess around 100 hz maybe about 3db in room. I used the EQ in Itunes to futz around here.

my room is notoriously bad sounding. the carpet on the relatively compliant floor, acoustic tile ceiling, huge window behind the speakers, ... they still sound great. they need a slightly smaller and much stronger room and they would be flat and quicker no doubt.

they are really pretty big speakers. the drivers sit at ear level when one is sitting up straight in an office chair. a tall sound. fun and involving.

these 166 es-rs i have had for a year now. they are really really starting to spread their wings now. though originally I considered it, I would not dream of phase plugging them, duct sealing, super tweetering, etc. the thin wool felt that partially covers the front of the magnet is all I need, maybe not even that. I have really come to understand that this banana plant fibre just takes a few seasons of humidity and temparature fluxuations to break in perhaps. even and perhaps especially in the E series stuff from fostex. there are not stricktly just hours to be logged. patience pays!!!! the tone of them now is so refined and so far divorced from their initial character, as refined as they were new. they have grown out of adolescence into young adulthood perhaps. there is alot of black in the black background, unlike when they were new. they can handle extremely complex music, totally debunking that whole single driver congestion stigma. there is alot more euphony in the tone - at all frequencies. there is perhaps some natural compression going on here. that as the cone weakens with age the loud stuff is not as loud, the quiet stuff stays relatively the same? eh who knows. I think that they are very very special indeed. so balanced, so super. very high speed. ultra detailed, especially harmonically. they are simply a good balance of what is possible. I enjoy the 168 sigma alot as well. the lack of whizzer makes it very special, still maintaining a decent top end response.

where the es-r has muscle is in the region of midrange to upper midrange. it sounds very errie. very very real and expansive. it will trick the mind time and time again. however, I feel that the 166es-r is somewhat unbalanced towards this area perhaps. that there is soooo much midrange clarity that it works to the detriment of the high frequencies especially. also, no matter how much bass there is, the midrange is just so pure that it dominates.

we as a diy community should make sure to convince fostex to maintain their relatively new policy of shipping the u.s. some of their special edition stuff.

well,

I really love horns! there is just so much logic behind back horns. so much elegance and simplicity of mechanism.

Ill get pictures to y'all soon. thanks for all the help on this adventure in musical experimentation. especially to terry cain for challenging and encouraging me so much.

Clark
 
Scott,

I think Clark is saying he likes his BIB's. Qu'elle surprise?

Jeff,

Just saw the Hemp page and wideload. Love the Monolith. The Dawn of A New Understanding. I also think the Hempcone would do justice to that monster.

Those BIG ones are calling to me. Anyone have any thoughts about using the wide side for the 6 inchers? That nice side could be put to good use for wave launch. Great work guys!!
 
Dan -did we forget to warn him that these things can be addictive? ;)

Interesting idea -once I've finished the current batch, I'll look into it some more with the ~6in drivers. I like wide baffle designs -many of the benefits of dipoles, without the drawbacks. Or so it seemed with my old test mules anyway. Martin's new OB sheet is very useful in this regard.

Re the Monoliths, the only problems I can forsee is trying to fit them through the door... watching 2001 with a pair providing the audio could be an interesting experience though!

Cheers
Scott
 
addictive, no doubt.

are the BIB for 208es as tall as the nessie mk3? some time I will build a nessie or two. they seem really cool. fairly simple too.

yes, I like them. very much. I have been struggling with the p-16s in these though. I cannot seem to find a placement that I am happy with. I originally mounted 7 per side, but they totally killed the bass. yanked them all out it got way better. I have been playing with 5 per side, then 2, then 1 in all sorts of locations. avoiding the number of death for good measure. I mean they DO come 5 to a package after all. anyways, they will help some frequencies and not others. usually p-16s are just what the doctor ordered for the mouth of traditional back horns. are these things just way different? any comments?

I have a small panel at the very top of the horn which is parallel to the back which is around 5 inches long. it is the same width as the internal baffle. in fact, it is the scrap peice I cut off the internal baffle to get the void in the bottom. in either case, it is sortof meant for directivity and stability of the large unsupported area at the top of the horn. I think it helps a decent amount to strengthen the cabinet. could this have something to do with the ineffectiveness of the p-16?


Clark
 
inrank said:
has anyone used a FR125s in a BIB (back loaded corner horn thing?).
what excatley is a BIB?

Greets!

You answered your own question. ;)

Anyway, measured Fs for this driver is 'all over the map', so I split the difference at 56.5 Hz:

L = 120"
SO, SL = same as the original
zdriver = 23.5"

GM
 

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Greets!

Didn't I already list which spec determines each dim?

Anyway, Fs determines the line's length. Sm combined with the pipe's net Vb sets the gain over 'x' BW, so all else being equal, the lower Fs driver will have a longer line length and its extra Vb 'fills' in the extra BW even though both have the same Sm.

GM