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

bluegti said:
When I built my pipes, I found it very hard to get the pieces to line up exactly. When I clamped, the glue was slippery enough to cause the pieces to move slightly. When I removed the clamps, I noticed places that aren't exactly lined up.


Greets!

Draw out where stuff goes and drill a few pilot holes just big/deep enough to hammer in short panel (ring) nails to use as alignment pins, bending them as required for a snug or flush fit. It doesn't take long and yields perfect alignment which allows you to glue up the entire cab all at once with minimal clamping if you want to (I use low stick masking tape, only using clamps for obviously warped wood), just be sure to use enough glue to ensure a tight air seal. Use a caulk cartridge loaded high viscosity/fairly quick setting panel adhesive to take full advantage of pinning.

GM
 
if the pieces shift youre using too much glue! get someone to hold the piece in position while you clamp, and if it moves get them to tell you and starrt over. You also dont need that much glue at all, a thin bead all the way down, then spread out with your finger THEN clamp, if you go slowly, you shouldnt have drifting problems.
 
The first BIB cabinet i built fell apart when i (stupidly) flipped it over. The center baffle fell out of position. I took it all apart and quickly drilled holes. Then i glued and screwed the whole thing together. The second cabinet was built quickly without problems using the glue and screw technique. In the end they both came out great... pics of unfinished cabs to come next week.
 
giantstairs said:

a question for the experts -- how does the beyma 8bx look as a bib candidate?

anyone familiar with this driver? i saw there is another thread about it but didn't see much of interest there. is it unsuitable for a bib because it is coaxial? the specs look good, of course i'm not really sure what i am looking for with this enclosure.:confused:

can't wait to hear impressions of the little tangbands, josh. they look great, and since you're traveling over here in spain you may want to fill your wine rack with some rioja reds. i can recommend a few good ones if you like... :)

scott, anymore impressions of the monacors?
 
Thanks for the info and pictures guys. By the way I am really surprised that most folks here are using just glue, clamp and liquid nails to make the joints. Only godzilla says he used wood screws.

Sometimes I hire professional carpenters and at other times I build cabinets myself, both for PA purpose and Hi-Fi. To give you an idea of the level of complexity, I have Bill Fitzmaurice's Tubas and DR300s among other designs. Those who are aware of these designs (eg., check the DR300) would understand the complexity.

What I want to say is that I always use glue and wood screws for all joints. Usually I go for butt joints; I drill holes just large enough for the stem of the screw on the horizontal piece and a pilot hole on the vertical baffle. The pilot hole prevents the wood from splitting. The screws used are special wood screws, threaded along the entire length and the pitch is a little wider and deeper. I set the torque on the screw driver so that on being fully tightened, excess glue oozes out of the joint. When constructed this way, with bracing, these cabinets exhibit minimal resonance.

I understand that the width of the BIB is small and the depth is braced by the cross panel, but I still wonder about cabinet resonance because at the joints, mating of wood to wood is not ideal, except if you have used clamps every 3" to 4" or so.

Your thoughts.
 
Hi,

The beta BIBs we would build (emphasis on we, I would have help) would be made from 'marine ply', we only have the less dense type and not 100% void free. After final tuning I'd go for better quality cabs.

W/out high quality plywood, I would settle with White Ash soild wood for the front, top, back, bottom panels, and the internal fold. There would be 'movement', but I think it's less significant if the width I would use is narrow, ie, < 12". The larger sides panels would use 2 x 12mm sandwiched marine ply. The acceptable quality is limited to that thickness. The solid wood panels would use dovetailed and/or mortise-tenon construction, and the side panels would be butt jointed/glued on the soild wood edges using 'biscuits'. What do you guys think? Any predictable setbacks with this type of construction and material choices? Thanks.

Regards,
fred
 
Not particularly; you already know the general character of the materials, and given that you're already thinking that a future enclosure's materails would be better quality, I'd just go ahead with your plan. It should be solid enough. I never found any problems with simple butt joints, providing you take them carefully and apply even pressure to aid the glue setting. Not that it needs much ~20psi should be plenty. All mine were built in this manner with white PVA wood glue, and they're pretty bomb-proof.

Re the Monacors (SPH-60X) they're superb little drivers. Very solid bass performance, nice clean mids (bit dark, but I'd rather that than over-bright) and they go up a whole lot further than the 1354 ever did. They need some power -SETs are out, unless your idea of SET is something with 211s, but a good PP, chip amp or a decent T amp will do nicely. They go with SS nicely too -I've run them off a cheap Rotel integrated, and they seemed perfectly content.
 
giantstairs said:
A question for the experts -- how does the beyma 8bx look as a bib candidate? Anyone familiar with this driver? i saw there is another thread about it but didn't see much of interest there. Is it unsuitable for a bib because it is coaxial? The specs look good, of course i'm not really sure what i am looking for with this enclosure.

Greets!

Not me, but I can tell you that BL, Mms, and Cms are off enough to make me wonder how accurate the T/S specs are, so as always YMMV:

L = 138"
Sm = 220"^2
zdriver = 30"

No, whether a driver is coaxial, etc. has nothing to do with what types of box loading are acceptable, and yes, from a BIB alignment POV this driver's PUBLISHED minimum T/S specs are near ideal.

GM
 

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Samuel Jayaraj said:
Thanks for the info and pictures guys. By the way I am really surprised that most folks here are using just glue, clamp and liquid nails to make the joints.

I understand that the width of the BIB is small and the depth is braced by the cross panel, but I still wonder about cabinet resonance because at the joints, mating of wood to wood is not ideal, except if you have used clamps every 3" to 4" or so.


Greets!

You're welcome!

Mechanical Engineering 101: Some things are counter-intuitive, mechanical fasteners weaken a joint since they reduce contact area and create a high stress point, aka 'hotspot', so a somewhat lossy adhesive engineered to match the construction material's MOE to matain it around the edges is best. If you drive, excellent examples of this in action are all around you on the highways........ commercial truck's basic containers, trailers are all just glued together.

WRT using clamps, I ROTFLMAO every time I see a pic of a cab that looks like it's being 'eaten' by some alien monster or someone posts that you can't have too many clamps because the builder either assumes its required or they read somewhere that for max bond structural integrity a high/uniform clamping pressure is required.

Bottom line, if you use screws, for best performance you should always use screw blocks rather than in the joint, just like every speaker building book I've seen recommends.

GM
 
Greets!

Thanks! I wonder if these are still valid since he says the published Sd = 216 cm^2 and the current specs lists 220 cm^2.

Anyway, no real difference in the BIB except it's better damped, ergo rolls off a bit quicker at Fp:

GM
 

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Greets!

Hmm, 'once more into the breach'...... this has been answered several times already in this thread in one form or another (all dims inside):

h = L/2
d = SQRT(Sm*SQRT(2))
w = Sm/d

Once you move away from this ratio the bend becomes increasingly compromised with increasing aspect ratio, so until if/when me or someone else designs a calculator to work it all out, I don't recommend deviating from this too much since it will affect all of its BW response due to morphing it into a big vent BR BLH alignment.

GM
 
DaveCan said:
Hello everyone, I've got the info for the line length and how far down from the sealed end for the fe108ez, but how to you find out all the dimentions like L x W x H for the cabinet? I will be using 5/8ths or 16mm material. Thanks Dave:)

hi dave, you can email me for my dims and i believe wilson offered as well, earlier in the thread. he used a bit more math to come at a shorter height where i just divided the line length in 2.

GM said:
Greets!

Thanks! I wonder if these are still valid since he says the published Sd = 216 cm^2 and the current specs lists 220 cm^2.

Anyway, no real difference in the BIB except it's better damped, ergo rolls off a bit quicker at Fp:

GM

thanks again gm! it looks like i may have to give these a try although those little monacors look tempting as well!
 
That is a nice looking plot for the Beyma. I always wondered about that unit, but it looks like some tweeter in there, not a compression unit, which would be tasty. Good SPL, some Xmax for a change, Beyma makes very good drivers, even the el cheapo 8/Ag wideband sounds really sweet on OB. Their large coaxials are very well thought out, and spex impressively.

Glad everyone is having fun, and many thanks to Greg for his continued sagacity, efforts, and overall charm!! :wiz:
 
GM said:
Greets!

Hmm, 'once more into the breach'...... this has been answered several times already in this thread in one form or another (all dims inside):

h = L/2
d = SQRT(Sm*SQRT(2))
w = Sm/d

Once you move away from this ratio the bend becomes increasingly compromised with increasing aspect ratio, so until if/when me or someone else designs a calculator to work it all out, I don't recommend deviating from this too much since it will affect all of its BW response due to morphing it into a big vent BR BLH alignment.

GM


For those of us who don't know a square root from a
Gant chart, I vote for some sort of embedded calculator
at the Bib site.
 
Hi,

I think GM's post should be linked in Zilla's BIB page:

http://www.diyaudio.com/forums/showthread.php?postid=942572#post942572

.. so that you guys won't be continually inundated w/ questions that tend to be redundant.:D


I'd just go ahead with your plan. It should be solid enough. I never found any problems with simple butt joints, providing you take them carefully and apply even pressure to aid the glue setting. Not that it needs much ~20psi should be plenty. All mine were built in this manner with white PVA wood glue, and they're pretty bomb-proof.

Thanks... I still not really final with White Ash, there are other wood types to choose from. I just have to research which has potentially less movement and have good density.

fred