Baltic Birch Plywood..
where on earth are you located? Commonly available in North America, sometimes available in Europe. If not, ask for "void free" guaranteed plywood. it will most probably be Baltic Birch, or ask for "marine grade" plywood, often glued with expoxy or other completely water proof glues and generally "void free"
Baltric Birch ply is usually made up of very thin ply's , usually 16-24 plys per inch thickness. Apple ply is apparently very good as well.
where on earth are you located? Commonly available in North America, sometimes available in Europe. If not, ask for "void free" guaranteed plywood. it will most probably be Baltic Birch, or ask for "marine grade" plywood, often glued with expoxy or other completely water proof glues and generally "void free"
Baltric Birch ply is usually made up of very thin ply's , usually 16-24 plys per inch thickness. Apple ply is apparently very good as well.
I know around here in central Ohio, you can't find it in the big box stores. Check with better quality wood working stores, possibly higher end lumber yards, though it's doubtful.
Not real easy to find the good stuff, took me a while to find it locally. You might be able to find in online and order it cut to size. Just a thought.
Best of luck.
Not real easy to find the good stuff, took me a while to find it locally. You might be able to find in online and order it cut to size. Just a thought.
Best of luck.
Hemp FR8
Hi all,
Can someone (Scott ?
) tell me the dims for a BiB with a HempAcousics FR8 ?
Do the marks as on page 14 in this thread still stand or ... ?
I'd prefer a square footprint, and as my room is 2,60 meters high,
the bigger the better
thanks in advance,
Empee
ps.
can you use metric dims ?
Hi all,
Can someone (Scott ?
) tell me the dims for a BiB with a HempAcousics FR8 ?Do the marks as on page 14 in this thread still stand or ... ?
I'd prefer a square footprint, and as my room is 2,60 meters high,
the bigger the better
thanks in advance,
Empee
ps.
can you use metric dims ?
You are just not going to find BB and Lowe's, HD or lumber yards that cater to the construction trade. You need to go to a specialty store. For instance, I get mine in Little Rock at Hogen Hardwoods. Hogen has BB in 5'x5' (150cmx150cm) and appleply in 4'x8'. They are nationwide, you may have one nearby. Otherwise, into the yellow pages under hardwood lumber.
Bob
Bob
FWIW, my local Home Depot has special ordered anything I've needed over the decades that their distributors carry and while I haven't actually ordered any 13 lam BB ply, they confirmed they could/would order me as little as one sheet. That said, I've since learned there's a local PlyMart that stocks it for slightly less, but it's quite a bit further away and with the price of gas now...........
Re: Hemp FR8
www.zillaspeak.com/bib.asp Look in the Hemp section. Alternatively, use the formulas established to create your own monster. All you need are the Fs, Vas & Qt of the driver, which with the FR8 are 45Hz, 88 litres (3.107ft^3) and 0.41 if you believe the published specs.
So, 7 easy stages.
1) L = 13526.5 / 2 / Fs
2) H = L/2
3) Vb = 20*Vas*(Qts^1.25) (this is the killer and the key calculation, that GM figured out based on a modified T/S alignment).
4) Sl = Vb (in ft^3)*(12^3 (inches in ft^3))/H
5) D = (Sl * (2^.5))^.5
6) W = Sl / D
7) Zd = L * 0.217
Where
L = internal line length
H = internal cabinet height
Vb = internal box volume
Sl = internal cross sectional area of the terminus
D = internal cabinet depth
W = internal cabinet width
Zd = distance of driver-centre to the sealed end of the line.
Yes, you can modify these to metric, or perhaps better, work them out like this, then convert & round up to the nearest practical figure.
Empee said:Hi all,
Can someone (Scott ?
Do the marks as on page 14 in this thread still stand or ... ?
I'd prefer a square footprint, and as my room is 2,60 meters high,
the bigger the better
thanks in advance,
Empee
ps.
can you use metric dims ?
www.zillaspeak.com/bib.asp Look in the Hemp section. Alternatively, use the formulas established to create your own monster. All you need are the Fs, Vas & Qt of the driver, which with the FR8 are 45Hz, 88 litres (3.107ft^3) and 0.41 if you believe the published specs.
So, 7 easy stages.
1) L = 13526.5 / 2 / Fs
2) H = L/2
3) Vb = 20*Vas*(Qts^1.25) (this is the killer and the key calculation, that GM figured out based on a modified T/S alignment).
4) Sl = Vb (in ft^3)*(12^3 (inches in ft^3))/H
5) D = (Sl * (2^.5))^.5
6) W = Sl / D
7) Zd = L * 0.217
Where
L = internal line length
H = internal cabinet height
Vb = internal box volume
Sl = internal cross sectional area of the terminus
D = internal cabinet depth
W = internal cabinet width
Zd = distance of driver-centre to the sealed end of the line.
Yes, you can modify these to metric, or perhaps better, work them out like this, then convert & round up to the nearest practical figure.
further queries on the 165 build
Greetings!
My perusings of this entire thread for the past month or two convinced me to build a BIB using the FF165K. I, in turn, convinced several others to do likewise. We were going to build two test mules out of 3/4" mdf based on both the short & tall parameters on 'Zilla's site. But that was before a friend suggested doing an inverted. So now we will test normal short & inverted short & various supra-baffles. Onto the q's (my apologies if these were previously asked/answered, but i could not locate such despite searching).
1.) Just inverting the box, the terminus becomes sealed by the floor & the driver is positioned at a mere ~27" from the floor. now if we extend the front baffle downward by 12", this raises the driver to 39" and the terminus is also raised by 12". Of course we add a leg to the centre of the rear wall of the spkr for balance. Sm is exactly the same as the normal BIB, but of course the 'squared look' of the side walls of the spkr are just awkward IMO. So, onto the T.C. staircased design or the wavy design of Edjosh. Doesn't this substantially increase Sm? If so, should I then compensate by decreasing the internal w & d, currently at 8" x 11" in order to maintain Sm at 88 in^2? or is the increase in Sm compensated by a line that's shorter than optimal?
2.) Is there any substantial benefit to the fitting of a pressure screw a la Herbert Jeschke (http://melhuish.org/audio/DIYTQ4.html)?
3.) It was suggested that a circular supra baffle on the order of ~14" dia would suffice for a driver of ~6" or ~7" dia. Is there any benefit/detriment for a slightly larger baffle, say of 16" dia?
BTW, many thanks to Scottmoose, GM, 'zilla & T.C. & numerous others contributing to this thread & design.
Greetings!
My perusings of this entire thread for the past month or two convinced me to build a BIB using the FF165K. I, in turn, convinced several others to do likewise. We were going to build two test mules out of 3/4" mdf based on both the short & tall parameters on 'Zilla's site. But that was before a friend suggested doing an inverted. So now we will test normal short & inverted short & various supra-baffles. Onto the q's (my apologies if these were previously asked/answered, but i could not locate such despite searching).
1.) Just inverting the box, the terminus becomes sealed by the floor & the driver is positioned at a mere ~27" from the floor. now if we extend the front baffle downward by 12", this raises the driver to 39" and the terminus is also raised by 12". Of course we add a leg to the centre of the rear wall of the spkr for balance. Sm is exactly the same as the normal BIB, but of course the 'squared look' of the side walls of the spkr are just awkward IMO. So, onto the T.C. staircased design or the wavy design of Edjosh. Doesn't this substantially increase Sm? If so, should I then compensate by decreasing the internal w & d, currently at 8" x 11" in order to maintain Sm at 88 in^2? or is the increase in Sm compensated by a line that's shorter than optimal?
2.) Is there any substantial benefit to the fitting of a pressure screw a la Herbert Jeschke (http://melhuish.org/audio/DIYTQ4.html)?
3.) It was suggested that a circular supra baffle on the order of ~14" dia would suffice for a driver of ~6" or ~7" dia. Is there any benefit/detriment for a slightly larger baffle, say of 16" dia?
BTW, many thanks to Scottmoose, GM, 'zilla & T.C. & numerous others contributing to this thread & design.
OK, before dealing with your points in turn, FWIW, my take on simple pipe-horns like the BIB is that the tall ones are best vented out the top, while shorter pipes, for smaller drivers with a higher Fs are best inverted. This in turn allows a different Zdriver position for the latter, which will be closer to the ~ideal. You can't do this with the tall pipes though, as the driver will end up way too high, so you just have to stick with the standard Zdriver location. I can't honestly see much point in inverting a tall pipe -chances are, you loose more than you gain unless you add complexity to the build. Anyway
1) No, chopping the terminus at an angle should not require any increase in Vb. All you've done is add a sudden slight flare to the terminus which if anything could help smooth the response a bit. Probably worth doing for any BIB to be honest -I like smooth curves myself.
2) Probably not with the Fostex drivers. They're much better built than the old 1354, and you'd have to drill through the internal baffle as well, which would be tricky, plus it would disturb the airflow when it's already a bit tight in there. Instead, I'd damp the basket and magnet with some ductseal, and a piece of felt wrapped tightly around the magnet. That makes quite a difference, and is easier to achieve.
3) Suprabaffle size is determined by baffle width and gain from the pipe-horn. You want step-loss to occur where you're getting a boost from the cabinet so they cancel each other out. In this case 14in diameter happens to be about right to balance the response of the shorter cabinet out.
Hope some of this helps
Scott
1) No, chopping the terminus at an angle should not require any increase in Vb. All you've done is add a sudden slight flare to the terminus which if anything could help smooth the response a bit. Probably worth doing for any BIB to be honest -I like smooth curves myself.
2) Probably not with the Fostex drivers. They're much better built than the old 1354, and you'd have to drill through the internal baffle as well, which would be tricky, plus it would disturb the airflow when it's already a bit tight in there. Instead, I'd damp the basket and magnet with some ductseal, and a piece of felt wrapped tightly around the magnet. That makes quite a difference, and is easier to achieve.
3) Suprabaffle size is determined by baffle width and gain from the pipe-horn. You want step-loss to occur where you're getting a boost from the cabinet so they cancel each other out. In this case 14in diameter happens to be about right to balance the response of the shorter cabinet out.
Hope some of this helps
Scott
Scott,
In some other thread you once posted
"...and they really do need to go in corners as the rear boundary condition increases the mouth area and decreases reflections back down the line..."
Would it be an idea to put something like a "deflector" on top of the cab?
just enough to prevent any reflected wave from reaching the bottom
plate directly ?
so that'd be over half the cab, see dotted line:
In some other thread you once posted
"...and they really do need to go in corners as the rear boundary condition increases the mouth area and decreases reflections back down the line..."
Would it be an idea to put something like a "deflector" on top of the cab?
just enough to prevent any reflected wave from reaching the bottom
plate directly ?
so that'd be over half the cab, see dotted line:
Attachments
well, to bad I haven't got the opertunity to corner-placement...
just a perfect flat, concrete ceiling wich I'm affraid will reflect
too much straight back into the pipe....
So I'm thinking of some way to prevent straight reflections entering the pipe
suppose I could make the backplate longer and than add a deflector
(no choking, just a boundary for reflections)
just a perfect flat, concrete ceiling wich I'm affraid will reflect
too much straight back into the pipe....
So I'm thinking of some way to prevent straight reflections entering the pipe
suppose I could make the backplate longer and than add a deflector
(no choking, just a boundary for reflections)
Attachments
Hi!
I have tested the deflector as you described. I lost bass as it was pointing forward. Not qualified guess is that you loose loading that way. Becomes more like a front loaded horn.
I tried also having the deflector pointing backwards. No loss of bass but some resonances in lower midrange was more prominent. So I went back to the normal mouth.
My BIB's are standing at a wall, also concrete, no corner loading. So maybe it will different with corner + diffusors behind speaker with deflector pointing backwards.
Peter
I have tested the deflector as you described. I lost bass as it was pointing forward. Not qualified guess is that you loose loading that way. Becomes more like a front loaded horn.
I tried also having the deflector pointing backwards. No loss of bass but some resonances in lower midrange was more prominent. So I went back to the normal mouth.
My BIB's are standing at a wall, also concrete, no corner loading. So maybe it will different with corner + diffusors behind speaker with deflector pointing backwards.
Peter
OK, without going too technical, it's not really the ceiling that's going to cause problems -the ripple is caused by the under-sized terminus and even against a rear-wall will be dramatically reduced as the mouth CSA is doubled by the reflection-boundary condition. You see it in all hybrid BLHs, chamberless or otherwise, to different extents when you reduce the terminus / mouth size, so ripple increases due to the impedence mis-match & various other things. Yes, you'll get some reflections, but their influence is relatively small compared to other matters. & your rear wall is already deflecting the energy away from the terminus.
Hi Scott!
I never thought the ceiling would be a problem, thats was not why I tested the deflector. My test was to reduce the mids coming out from the mouth. I believe that with some kind of diffusors (not damping) on the walls/ceiling would work. (SAF is in play here) My goal is to take away damping in the speaker!
Cheers
Hi
I have a pair of Fostex FE126 drivers, and I was planing to build Frugal horns for them, but after reading this thread (well, most of it) I changed my plans in favor of the BIB.
While googling for bibs I found two 3d models (done in google sketch up), both of them for 126/127 drivers.
One is normal BiB and the other one is inverted design with K slot which is mentioned earlier in this thread.
The designs are consistent with info on www.zillaspeak.com (and the excell sheet I found in this thread). So I will go for one of these.
I really need you opinions. Which do you recomend?
The inverted design looks nicer to me, but I don't know how the floor loading and K slot compares to normal design. The placement needs to be as close to the wall as possible (not in the corner) - and I don't know if that is recomended for floor loaded version (especially concidering the slot in the back)
I don't know who is the author of these models (google says anonymous) so I can't credit them. Sorry
and, thank you very much for this thread - it's full of good info..
I have a pair of Fostex FE126 drivers, and I was planing to build Frugal horns for them, but after reading this thread (well, most of it) I changed my plans in favor of the BIB.
While googling for bibs I found two 3d models (done in google sketch up), both of them for 126/127 drivers.
One is normal BiB and the other one is inverted design with K slot which is mentioned earlier in this thread.
The designs are consistent with info on www.zillaspeak.com (and the excell sheet I found in this thread). So I will go for one of these.
I really need you opinions. Which do you recomend?
The inverted design looks nicer to me, but I don't know how the floor loading and K slot compares to normal design. The placement needs to be as close to the wall as possible (not in the corner) - and I don't know if that is recomended for floor loaded version (especially concidering the slot in the back)
I don't know who is the author of these models (google says anonymous) so I can't credit them. Sorry
and, thank you very much for this thread - it's full of good info..
Attachments
Re: further queries on the 165 build
The holey brace tightly coupling the driver to the box (in this case you run a brace from driver to partition, and then the other side of the partition to the back of the box) was partly inspired by Herb's trick, and i'd recommend it, even just as panel bracing (just don't put it dead centre)
dave
geetarman said:
The holey brace tightly coupling the driver to the box (in this case you run a brace from driver to partition, and then the other side of the partition to the back of the box) was partly inspired by Herb's trick, and i'd recommend it, even just as panel bracing (just don't put it dead centre)
dave
cheda13 said:
For some reason -- even thou logged in google didn't capture my name ...
When i started thinking about the BIB for 126/127 the short hieght encouraged me to invert them to take advantage of floor loading since the ceiling would be far away (the brown render preceded the purple one). Further, the idea of k-slots had been thrown around (here or on the Full Range Forum) and i realized it might well work to ameriolate the one problem i had with the one set of BIBs i had heard -- ripple was noticable especially in direct comparison to A126, Frugel-Horn or Fonken.
The dimensions are taken right off Jeff's site -- IIRC these are the bigger version.
When BIB gets to the top of our queue we will be doing the iBIBk with side slots -- Dave Cigna suggested that IIRC.
dave