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

Hiya Terry, good to hear from you again!

I've sent an email to the guys at eifl in Japan regarding those Craft Handbooks -just waiting on a reply, so here's hoping that they're back in print, as I understand the basic idea / theory behind this box design is in one or both of these (not sure which, so it looks like I'll have to get both). Perhaps I should get the old slide-rule and graph paper out in readiness, just in case. There is much to be said for the old fashioned way on occasion, I admit.

Without having the Craft Manuals to optimise things, but extrapolating a bit using what I can of Martin's MathCad worksheets, I thought I'd share a few box dimension ideas with you guys for a BIB with the FE168ESigma and the Supravox 165LB. Still work in progress, but this is what I've come up with so far. All assume 3/4" material (because I'm in the UK, and 1" is impossible to find, and, if you did, would be impossible to afford. Modify the dimensions accordingly if you wish to use 1") and I've tried to keep the boxes of a domestically acceptable size.

Sigma first. The driver specs suggest a shorter line-length here, so I'd decrease it by a foot, which will reduce the overall cabinet height by 6", down to 64". A little shorter less than the Fs suggests (that'd be 66 1/2", give or take), but it's a nice round number, and it's still going to be tuned pretty low! If you want to keep the 7" width (already with 3/4" material giving us a little more breathing room), then I'd increase the depth of the cabinet to an external depth of 17 1/4". Take the internal baffle from its starting position to where it terminates, in the internal centre, 7 1/2" from the base and 7 1/2" from the internal face of the front and rear baffles. Driver mounted at 35" from the base. These are still only approximate, but I suspect they should let the Sigma breath better than the original. You could chop the rear down a little too if you wish. If you wanted to do it another way, I'd use external dimensions of 8"x14 1/4"x64", with the internal baffle ending 6" from the base and 6" from the internal walls of the front and rear baffles.

On to the Supravox. Their specifications indicate an Fs of 69Hz, which would mean substantially reducing the height of the cabinet -not in itself a problem, but it would mean the driver would be mounted too low -only around 25" give or take from the base, which isn't anywhere near enough.

Ok, some thoughts. The first thing that struck me is that while the original 1354 Terry used is supposed to have an Fs of circa 50Hz, I recall that it was frequently measured at around 70Hz -very similar to the Supravox in other words. But it still worked well, yes? Therefore, especially considering the considerable excursion of the Supravox, which should hopefully give us a wide safety margin, we should be able to go for the same line length that was used for the little RS driver. That's my take on it anyway. So, I'd try using Terry's original 140" line length and 70" overall cabinet height. Driver positioning remains the same too at 39" from the base. However, I'd use the increased depth of the first idea mooted above for the Sigma mated to the higher cabinet if the 7" width is to be preserved, to end up with external dimensions of 7"x17 1/4"x70". If a wider cabinet is wanted, then mate the width and depth of the second idea for the Sigma mentioned above to the taller cabinet.

If the over-long line-length for the Supravox causes palpiatations, or nervousness, then try a milder version (BIB korma?). Keep the same depth and width of either of the two versions above, but reduce the overall cabinet height to 60", with the driver mounted 31 1/2" from the base.

That's it so far guys. Any comments and / or suggestions will be welcome as always.

Cheers for now
Scott
 
Having finally thrown off (most of) a cold, I've finally been able to roughly complete the new pair of boxes with the original dimensions. Roughly, because 1) The materials I used as an experiment haven't worked as well as I'd like, and 2) I reckon that the larger drivers want a bit more breathing room. It has, however, allowed me to try out the FF165K in the load.

Oh me of little faith. Again. Until I built my first pair, I didn't believe this cabinet design could work, and I was delighted to be proved wrong (always nice to learn something new). Now I didn't think these drivers would work, and I've been proved wrong again ;-) They do work. And how. The limited Xmax doesn't appear to be an issue, and according to my cheap SPL metre, in my room at least the response just isn't rising at all; not with EL34s driving them at any rate. I suspect that SS amps could need some series resistance, but that's going to depend on the room and amplifier. Very little ripple too. They'll nicely complement my ML TQWTs built to Martin's Project 2 design. I'm a happy camper. Oh, the bass-end? These things shake the furniture. You feel the low frequencies in your chest, and there no boom; it sounds almost like dipolar woofers.

My dimensions for the cabinet using the FF165K -this is what I'll be building for them anyway after thinking it over for a while and deciding not to wait for those Craft Manuals:
-Box height: 68", Total line-length: 136", External box width: 8 1/2", External box depth: 16 1/4", Baffle centred at 7" from base and 7" from front and rear internal baffle walls, Driver centre mounted at 36" from the base. Any thoughts on build materials guys? MDF alone isn't optimum, I was thinking of a good ply of some description, but a decent hardwood perhaps, if it can be acquired in the required sizes (I'm in no position to build up panels)?

Cheers for now
Scott

PS: Has anyone else tried placing an acoustic guitar on a stand between a pair of speakers when listening? If you haven't, and there's one in the house, try it. Rather enlightening when listening to John Williams.
 
Well, there it is again. Audio Alchemy. The Fostex FF165, with its almost nonexistent Xmax, and ...."shakes the furniture." No boom, and "almost like dipole woofers."

This morning there was a package at the door whose origin is Frankfurt, Germany. This could only be the Supravox 165LB, linear Xmax 6mm. It will be VERY interesting to see what happens with these.

Glad you like your new creations, Scott. Which EL34 are you using?
 
I don't know why the FFs work, but they seem to. I haven't really punished them with something like Floyd yet, I admit, but nor have they bottomed out on anything. More excusion would be nice, that's my only slight concern, but thus far it's not been an issue. I look forward with interest to learning how they perform in the load compared to the Sigmas. My bet is they'll beat the Fostex units.

My valve power amp? It's a World Audio Design KAT34 with Svetlana valves. WAD have probably the best output transformers out there, until you get to the suicidally expensive stuff. Their 300b monoblocks look hugely tempting -they were designed by Andy Grove, the bloke behind the latest incarnation of the Ongaku.

Cheers
Scott
 
Hey Dan, hope those Supravox drivers have arrived safely; I'm looking forward to hearing your first impressions when you've had time to get them into the cabinets!

A couple of drivers I completely forgot about that look to be interesting options for the original cabinet: the 5" Fostex FX120 and F120a models. The FX has a 2mm Xmax, Fs 70Hz, 0.45 Qts, 8.4 Qms, 0.47 Qes, and a low 8.21L Vas. Quite cheap too. The F model has a 1.5mm Xmax, 65Hz Fs, 0.44 Qts, 3.1 Qms, 0.51 Qes and another low Vas of 9.876L.
Both specs appear to be quite similar to the RS 40-1354 Terry used for his original pair of pipes, but I bet the quality's better over the rat-shack models! Of the two, the FX120 looks to be my favourite from the specs -it rolls off more smoothly, and seems generally flatter; extremely tempting, expecially as it's very reasonably priced. Either way, both look like nice mid Q types with reasonable excusion for their size. Any thoughts?

Scott
 
The 165LB are beautiful to behold, better build quality than the 215 IME, and one thing I like is the very heavy driver flange, which would double as a mass loader, for the diaphragm. At first blush they seem quite rolled off, and their 30' FR plots would indicate same, according to the site. FWIW, green, I do not put these in the same sonic league as the Fostex. I plan to let them cook a few days before deciding to proceed further. Not a good feeling about this one.

Scott, have a look at the 5 inch Monacors as well if you would, the two 6- models measure flat, and someone I know here building speakers is really stunned by the performance of the 8 Ohm unit. Says they are incredibly well built, and impressed everyone who heard them recently. Fs/60Hz Qts/~.45. Price is around $20. as opposed to $175 for the Supravox.

www.monacor.com

For the open baffle experimenters, Monacor has apparently released several new models with high Q, and according to the in-house measurements at www.spectrumaudio.de measure very impressively flat, all the way out.
 
Last offering regarding these pipes, as I think I can now suggest how they are sized, which might be of use to someone.

Total line length, as we all know well enough, is set to 1/2 the wavelength of Fs. Generally. You can play with that -this is probably best followed for drivers circa 50Hz lower, and you're going to get a L-O-N-G pipe indeed.

They are So=0 pipes (we all have exceptions to out rules, and this is mine!), Sm terminates in free space, and is set to approximately 4.25Sd. I say approximately, because there's room for experiment there. That said, based on Martin's explanation of the acoustics, and Terry's suggestion of chopping the back down to increase the mouth area a bit (though I have a hunch that he suggested this more for those running 6"+ drivers in the original pipe, which was designed for the 5 1/4" RS 1354), I wouldn't think going lower would be advisible. Increasing it by perhaps 1/2Sd will probably be OK though. Where the internal baffle ends depends on construction material. It'll terminate in the mid point of the cabinet, the same distance away from the floor.

Driver height appears to be determined by ye olde Voigt pipe equation: D = L + the cube root of So / Sm. It'll usually work out to be around 0.275 of the total line length. Stuffing depends on the room and driver. The point needs a bit, and about 1/4lb or an inch or so of felt on the base would most likely be a good starting point.

And that's it! Easy eh?

At present, my BIBs with FF165Ks in them have now got a few hours on them, and are really starting to open up, though with an Xmax of 0.3mm, I'm tredding easy with Iron Maiden! The new cabinets will be built to the above spec, though I won't be going for a 1/2 wave fs -that'd give a height of around 84", which is I feel a little excessive for a 6 1/2" driver! The FE206E, with its 1.5mm Xmax on the other hand, and a similar Fs would be interesting indeed, though you'd need a big room... I'm currently (no pun intended) using 24AWG magnet wire to good effect with EL34s doing the driving, though I think 30AWG would be more appropriate with an SS amp. I might also try a single pair of Cat5, just to say I've done it! How much series resistance, or how thin a wire you use (or what sort of cap etc) will largely depend on your amp, and what Q the driver you're using is.

Have fun!
Regards to all
Scott
 
Scott, quick thought on wire. I am a cat 5 user at this point until I make time to cut into my 47 labs length of wire. Anyway, I currently use 1 run of cat 5 in the casing in comes in per side, which is 4 wires per side. (4 twisted pair running though the outer casing) The correct way to do it is to simply seperate the twisted pair on each end and mate the solids and stripes. (this helps eliminiate RF and such, each twisted pair IS actually twisted at a different rate) Strip the ends and there you have it. Pretty easy. I've used this with both tubes and SS with success.

I had tried one twisted pair per speaker and found the sound was much leaner and really didn't gain anything. In fact, lost some of the body and weight.

Just thought I'd share, curious as to your thoughts once you try it out.
 
terry's BIB plans

Hello all. New to this site and to DIY FR speakers. I've read most of this tread and tried to wrap my head around it but its alot for a newbie. So now I have a question, first are the plans for the BIB pipes (second piture at the single driver site under BIB) available and two could the pioneer B20"s be used even though they are 8 inchers.
I plan on putting them in our living room (14'x16' w/ 8' ceilings) I like the idea of an open pipe and using the ceiling to disipate sound but everything i've read on the B20's says they suffer at the high end and I would rather not use a tweet and crossover, is there an other solution? What would be the most accessable inexpensive driver for these pipes?

Mark
 
For the price the Pioneers are an excellent driver, though stock they do lack a bit of treble, and they'll need a hefty cabinet. Approximate dimensions (assuming I'm correct in how these things are sized): 78" tall, 8 1/2" wide, 21 1/2" deep (external). Driver at 41 1/2" from the base. Internal baffle terminates 9 10/16" from the base and front and rear walls. Bass will be very heavy -probably overly so.
It'd be worth saving up for either the Fostex FE166E or FE167E -smaller cabinets, better quality. Well worth it in the long term. You need rear walls or preferably corners to load these cabinets by the way, or you'll get 0 bass and an rough midrange

Best
Scott
 
In my experience with the big pipe designs such as the BIB, they are very forgiving of driver swapping and will happily go from a 6" to a 8" without to much trouble. If designing from scratch then it all the easier. Small cabinets are much more critical and need careful dimensioning.
With regard to adding a tweeter, if the Pioneers behave up to 10KHz then it is very satisfactory to roll in a small tweeter with a simple cap crossover, with maybe a bit of resistive padding. Trial and error can take some time, but the end result are well worth it over letting a treble challenged driver struggle on its own.

Personally I would rather go with a large driver with a helper tweeter, than a small driver with a helper woofer, as the helper woofer will be much more challenging to cross over satisfactorily.

Shoog
 
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hey, I like the dog by the way! Yes, I'd agree to an extent, and these pipes are pretty forgiving within reason. The original cabinet works OK with the FE166/7, though it's a little small for them, which I suspect is why Terry suggested chopping the back down a bit to increase the mouth area. I would advise against trying the Pioneer in the original cabinet though, assuming you can get them to fit -some kind of large false baffle will be needed to support the surround and frame, and I reckon they'd sound very choked. Length won't be a problem, but I think the cabinet volume and Sm size or lack thereof will be.

Another option though that could be very interesting: the Tang Band W4 1320SB bamboo coned 4" drivers. Their specs look excellent (and that's a real compliment, coming from me), and perfect for a scaled down version of this TQWT (they look cool too!). They cost $40 each, about mid-way between the Pioneer and the Fostex, so could be achievable on a small budget.

Try with these cabinet dimensions (assuming 3/4" build material) of: external depth: 10 1/2". External width: 5 1/2". Cabinet height of 60" and an overall line length of 120". Driver mounted 31 1/2" from the base. That's a bit long for them, but the original cabinet was over-long for the RS drivers, and as these Tang Bands have a very considerable 3mm Xmax, they should be OK with the load, and also have enough excursion to produce reasonable bass. I'd guess a cut-off point of around 40Hz in-room -not bad for a little 4" driver methinks. In fact -I think I'll buy a couple myself and give it a whirl. And no, I'm not joking!

Cheers for now
Scott
 
I second the new bamboo TangBands. The anecdotes are coming in over on fullrangedriver, and they are all good. Really good accounts of that little driver. Another one which should be assessed, is the 5" Monacor, Fs/60 Qt/45, and Louis Chochos of Omega says it is right now his favorite small driver, and by a long shot. they can be had from Monacor or Spectrum Audio for about $18-


My 168Sigma Pipe cabs are coming back to me tomorrow. I decided that I would hand over my nice plywood blanks to a shop I know, with a large table and large stroke sander, to get things right, as I had already cobbled up a mule this summer: A+++ ...the nice ones get the treatment this time, 3/4 roundovers on the back, nice dark stain Cherry wrap, and I will eventually get around to turning a 12.5 inch concentric baffle, (this DIA is the author's reco').... this will come once I find some truly outstanding 1 inch figured hardwood. Having owned the Abbys and auditioned BEN and I'm Ben, I know the sound. As far as helper woofer and tweeters, the 168Sig in a BIB needs neither. All you seem to need are some healthy Xmax and an Fs<~60Hz, IME...Mid Q is ideal as well. ... Nor do most 6+ inch drivers anyone has shoehorned into these loads. Stuff them into corners, or into an alcove as a chef in Walla Walla Wa., does, and apparently the bass is LARGE and in charge, with nary a hint of hangover, hollowness, these things yield an amazingly effortless and FAST sound. They are my favorite "horn" sound.
 
Ah yes, the Monacor! Sorry Dan, you asked me to look into that 5" job before, and I'd clean forgot, both the request, and about it's existance! Well, I've had a look now (GOOD reminder, especially in the circumstances). From the specs, and the pictures... what a GREAT little driver! Added bonus: they're going to work well in Terry's original cabinet, no changes needed. Well, ok, we could alter the dimensions a bit, slight reduction all round etc, but they're so close to the RS drivers I don't honestly think it'd be worth it. Use and enjoy I say. And with that price, you'd be laughing. Better, you could upgrade to the FE166/7E or even the FE168ESigma when funds permit. The cabinet wouldn't be optimal, but it'd still sound spectacular.

By the way, the dimensions I posted for the Tang Band drivers (I must try them out -they look brilliant at the price. I'll order a pair and a pair of the Monacors too as they're not going exactly going to break the bank ballance) should suit the FE108ESigma as well, though I'm not sure how well it would work -the Sigmas have even less Xmax than my FFs, and around 1/3 the cone area, so I suspect bass is going to be pretty light, and it could be easy to overdrive them. Tread warily, but could be good.

Then again, Terry suggested driver rolling with these cabs. didn't he? Well, as we do it with the larger cabinets, there's no reason why anyone who can't stretch to the verious 6 1/2" Fostex drivers who still likes and want's a BIG TL/Horn hybrid sound couldn't do the same with a scaled down cab like the one I detailed above for Tang Bands, smaller Fostex units etc, or those those upcoming smaller Hempsters etc. Could be a real winner. I forgot to mention where the internal baffle terminates if anyone wants to try it: dead easy; 4 1/8" from the floor and front and rear walls.

Great fun!

Cheers
Scott
 
Scott thanks for your repliy, about the pics at http://melhuish.org/audio/DIYTQ8.html he states this "accepted design methodology for TQWT in that the flare extends a full 140" and is unobstructed at the top of the cabinet. " Is he talking about the top pic or the second pic? If I understand this correctly this cab is almost 12 feet high!!! and open (unobstructed) at the top where the front and back panels come together, is this correct?? Cause I'm kinda lost here (remember me newbie) first who has 12 foot ceilings? and if they are to meet together front and back how can it be "unnobstructed" or is he just telling us ther is nothing else but wall behind the cab!! Way confused!!! Also what is line lenght? Yes I have thought of the tang bands but they will be pricey to get to my door B20's will be almost $100 CDN with shipping. What about a tang band in a zigmahornet!! (plans at planet 10 hifi).

Mark
 
The completed cabinet is seen in the first picture. (ignore the second, that's just a Voigt Pipe, and well worth ignoring, except to admire Terry's gorgeous cabinet work) The design for the BIB is shown in the CAD screen shot at the bottom of Terry's article, which provides the basic layout for you. I've attached a tagged version of this to the bottom here, which might help.

Basically, the original BIB cabinet is a rectangular box, 70" tall, constructed from 1" thick material. Attatched to the inner surface of the front panel (or baffle, if you prefer), is a sloping, internal baffle, that in effect splits most of the cabinet in two, a front part, and a rear part. This baffle descends diagonally downward through the cabinet until it finishes, 5 1/2" from the floor, and 5 1/2" from the front and rear walls. The That's where the 140" flare comes from -the flare begins at the pointy top, runs to the bottom of the cabinet in the front part, then all the way back up again in the rear part. The top is left completely open, and that forms the vent / horn mouth. So in a sense you were partially correct -it's a 140" tall TQWT that's been folded in half to keep the size down to a managable, but still considerable 6 foot. I'll try to draw a clearer diagram, but I'm afraid I don't have any CAD software, and I'm not too great at such drawings (perhaps we should ask Dave [planet10] nicely, though I suspect he's snowed under with different cabinet designs at present!) I've added a few tags to Terry's original CAD drawing below, which might help.

I know the Zigmahornet, having built two pairs, one for a friend, one for myself, which I actually sold a few days ago after reciving an offer I couldn't refuse. I couldn't say how well the Tang Band's would work in a Zigma, but the Fostex FE103E they were designed for costs less than the TB drivers, so I'd just use those. They work very well indeed, but are utterly different in their presentation to the BIB boxes -for a start, they have no bass at all, as you'd expect from the tiny cabinet size, though they image like nothing else on Earth, and their midband is superb.

Depends on your priorities about what you go for. Both are great. If you went for the BIB, then with your budget, I'd suggest that you use the 5" Monacor drivers Dan mentioned above in the original cabinet. If the Zigma, Fostex FE103E every time.
 

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Thanks, Scott excuse my lack of gray matter I'm on the midnight shift. If you had to pick a cab for the B20's, Fe 130e or tang bands what would they be? I need narrow cabs (12"-16" wide) for a 14'x16' room. Should be budget conscious and easy to build.

PS Why sat away from voight pipes?

Mark
 
Hi Mark

Last bit first -why not use the Lowther Club of Norway Voigt Pipe? Well, quite a few reasons. The primary reason in my view is that it comes to a point at the top, and unlike the BIB box, its mouth is not positioned in such a way as to negate the problems this causes. The Voigt Pipe has a very high cut-off -much higher than it needs to be, and a very jagged frequency response. Best avoided.

Keeping your budget in mind, and the fact that this is your first project, so we want to keep it as simple as possible, I'd either go for the FE103E in the Zigmahornet, or the Fostex factory horn, which you'll find here: http://www.fostexinternational.com/docs/speaker_comp/pdf/recom_enclose/103e_encl.pdf.
Alternatively, if you want more bass, I'd try the Tang Band in the downsized BIB cabinet I mentioned above, or the 5" SPH 60X Monacor driver, which looks a brilliant buy at the same price as the Pioneer (you'll find it here: http://www.monacor.com/int/en/produktseite_gesamtprogramm.php?artid=2152&spr=EN&typ=u ) in Terry's original cabinet. The B20 is fine, but perhaps not quite in the same league as the others, especially over the all-critical midrange; I think you'd be better off with one of them.

Best
Scott
 
From the sounds of it, either the TB or the Monacor will yield a sound quality far above what you might expect from a "project" speaker. The Omega M5 uses the Monacor, and I heard that it floored a room full of people at a Zu Definition demo in PA, recently. All commented on the full and strong bass coming from a diminutive BR cabinet, so in a BIB, using at least 25 watts should get you very good bass response, she's a true bassmaker, and just a wee bit polite on top, but likely voiced that way for inexpensive digital sources likely to be paired with it. For a good pic of the Monacor 5, www.omegaloudspeakers.com Very sweet cabinet work in Ebony...