ok... i want to build a BIB fe167e.
I do have the link to the general position where the driver needs to be mounted and length of the line.
question is how wide and deep and high should the enclosure be???
also... do i need a baffle step filter on these?
basic questions i know.
finally, what thickness and type of wood should i use?
any stuffing?
Thank!!
I do have the link to the general position where the driver needs to be mounted and length of the line.
question is how wide and deep and high should the enclosure be???
also... do i need a baffle step filter on these?
basic questions i know.
finally, what thickness and type of wood should i use?
any stuffing?
Thank!!
Rich, are you familiar with Godzilla's BIB page?
http://www.zillaspeak.com/bib-howtobuild.asp
I think for the driver you mentioned you're going to be around 68" tall, and 8" wide by 12" deep ID. This assumes 3/4" material.
Scott, MG, and the others can tell ya for sure but I think those are your dimensions.
Rick
http://www.zillaspeak.com/bib-howtobuild.asp
I think for the driver you mentioned you're going to be around 68" tall, and 8" wide by 12" deep ID. This assumes 3/4" material.
Scott, MG, and the others can tell ya for sure but I think those are your dimensions.
Rick
I have the same driver and was thinking about maybe building this also. With L=136", Z=27.5" and Sm=87.75^2" from Zilla's page, I came up with the final length of 68" and 8"x11" (WxD) for the internal dimensions. External dimensions will be a bit bigger due to the wood thickness. The internal baffle length will be determined by mid points near the bottom as explained in the web page.
I think it would be helpful if Zilla's page should how to calculate the width and depth. IIRC the width/depth should equal .707. So in my case 8/11=.727 with Sm=88^2". Close enough, I think...
Also, the length might have to be a bit longer due to the terminus of the internal baffle taking up some line length. Again this is an "I think" assumption.
Hope this helps, or ignore all of this if I am completely off track!
A little help please if I am...
I think it would be helpful if Zilla's page should how to calculate the width and depth. IIRC the width/depth should equal .707. So in my case 8/11=.727 with Sm=88^2". Close enough, I think...
Also, the length might have to be a bit longer due to the terminus of the internal baffle taking up some line length. Again this is an "I think" assumption.
Hope this helps, or ignore all of this if I am completely off track!
A little help please if I am...
That agrees with the recommendation of just using L/2 as the inside height. I worked out the geometry and found that this results in an enclosure that's close, but not quite long enough. I'm not sure if the 'error' is significant...
The approximation made using L/2 is that the path around the fold is equal to D. Making the approximation that the path around the fold is a semicircle (still an approximation, but a better one I think) I find that part of the path to be close to pi*(D+T)/4 where T is the thickness of the sloping divider and D is the inside depth of the cabinet.
The difference between the two approximations is D - pi*(D+T)/4. For D=11 and T=3/4 inches that works out to be a about 1.77 inches.
You also lose a much smaller amount due to the fact that the opening in the top of the cab is horizontal. Looking at a cutaway drawing from the side, draw an imaginary line right up the center of the rear section. To match MJK's model the mouth should be perpendicular to this center line; the back of the BIB should be a little taller than the front. As far as I can tell the tiny bit of difference in length is about D^2/4L.
The little bit of line length that you lose is really small; less than 1/4 inch with D=11 and L=136 and I'm sure it's not worth worrying about on its own. But if we're making corrections we might as well throw it in. In fact, the two corrections add up to almost exactly 2 inches. So, for this particular design, I would make the inside height 1 inch taller than L/2 or 69 inches. (You gain an inch going down the front section and another going back up the rear.)
As for A=B=C=D/2 (see the drawing at http://www.zillaspeak.com/bib-howtobuild.asp) I figure that A should be smaller than B by approximately (pi/4)*(D^2/L). In this case it works out to be about 0.7 inches. That means moving the end of the divider a measly 0.35 (~3/8) inches closer to the front of the cab. C should be about half way in between the two.
Will any of this make a bit of difference to the way the thing sounds? Probably not, but refinements are OK, aren't they?
And, I know that it's irresponsible of me to give these results without showing the derivations, at least so that people can check my math, but that would require me to make nice clear drawings. I'm too lazy on this Sunday morning. I might get around to it if anyone actually cares, and they probably shouldn't as the already recommended approximations (L/2 and A=B=C) are probably more than good enough.
-- Dave
The approximation made using L/2 is that the path around the fold is equal to D. Making the approximation that the path around the fold is a semicircle (still an approximation, but a better one I think) I find that part of the path to be close to pi*(D+T)/4 where T is the thickness of the sloping divider and D is the inside depth of the cabinet.
The difference between the two approximations is D - pi*(D+T)/4. For D=11 and T=3/4 inches that works out to be a about 1.77 inches.
You also lose a much smaller amount due to the fact that the opening in the top of the cab is horizontal. Looking at a cutaway drawing from the side, draw an imaginary line right up the center of the rear section. To match MJK's model the mouth should be perpendicular to this center line; the back of the BIB should be a little taller than the front. As far as I can tell the tiny bit of difference in length is about D^2/4L.
The little bit of line length that you lose is really small; less than 1/4 inch with D=11 and L=136 and I'm sure it's not worth worrying about on its own. But if we're making corrections we might as well throw it in. In fact, the two corrections add up to almost exactly 2 inches. So, for this particular design, I would make the inside height 1 inch taller than L/2 or 69 inches. (You gain an inch going down the front section and another going back up the rear.)
As for A=B=C=D/2 (see the drawing at http://www.zillaspeak.com/bib-howtobuild.asp) I figure that A should be smaller than B by approximately (pi/4)*(D^2/L). In this case it works out to be about 0.7 inches. That means moving the end of the divider a measly 0.35 (~3/8) inches closer to the front of the cab. C should be about half way in between the two.
Will any of this make a bit of difference to the way the thing sounds? Probably not, but refinements are OK, aren't they?
And, I know that it's irresponsible of me to give these results without showing the derivations, at least so that people can check my math, but that would require me to make nice clear drawings. I'm too lazy on this Sunday morning. I might get around to it if anyone actually cares, and they probably shouldn't as the already recommended approximations (L/2 and A=B=C) are probably more than good enough.
-- Dave
Pay Bob Brine US$25 for details of plans and design, also the pit falls to avoid.
see website below.
http://geocities.com/rbrines1/
cheers..
see website below.
http://geocities.com/rbrines1/
cheers..
Re: umm...
That's right. Don't forget to add the thickness of the sloping divider. So, if you're using 3/4 inch material then the outside dimensions would be 9.5x13.25
As far as I know real Baltic birch is available only in 60x60 inch sheets. You can get good quality plywood in 4x8 foot sheets. The trick is to find something that uses good plies throughout. The thing I know about the Baltic birch (from using it years ago in cabinet work) is that it is VERY high quality. I don't know if there's anything particularly special about birch tonally. Maybe, I don't know.
You can get 4x8 sheets of birch and maple ply at most large home centers (i.e. Home Depot) but lookout for voids in the inner plies. You can gauge the general quality by looking at the edge of the sheet. There was a local chain of home centers near here that sold mahogany ply. Obviously, just the outer veneer was true mahogany, but the inner plies were something similar (probably luan) and pretty good quality. Best of all, the stuff was cheap. It was probably manufactured in South or Central America where large old growth trees still exist ... It seems to me that it would make a very nice material, especially if you like the deep red color.
Anyway, after looking at what Home Depot (or where ever) offers, you might want to look in the yellow pages for hardwood dealers. Most of the larger ones sell high quality 'furniture grade' plywood including Baltic birch. You might be shocked at the prices. OTOH, you might find something appealing.
-- Dave
AudioGeek said:
That's right. Don't forget to add the thickness of the sloping divider. So, if you're using 3/4 inch material then the outside dimensions would be 9.5x13.25
As far as I know real Baltic birch is available only in 60x60 inch sheets. You can get good quality plywood in 4x8 foot sheets. The trick is to find something that uses good plies throughout. The thing I know about the Baltic birch (from using it years ago in cabinet work) is that it is VERY high quality. I don't know if there's anything particularly special about birch tonally. Maybe, I don't know.
You can get 4x8 sheets of birch and maple ply at most large home centers (i.e. Home Depot) but lookout for voids in the inner plies. You can gauge the general quality by looking at the edge of the sheet. There was a local chain of home centers near here that sold mahogany ply. Obviously, just the outer veneer was true mahogany, but the inner plies were something similar (probably luan) and pretty good quality. Best of all, the stuff was cheap. It was probably manufactured in South or Central America where large old growth trees still exist ... It seems to me that it would make a very nice material, especially if you like the deep red color.
Anyway, after looking at what Home Depot (or where ever) offers, you might want to look in the yellow pages for hardwood dealers. Most of the larger ones sell high quality 'furniture grade' plywood including Baltic birch. You might be shocked at the prices. OTOH, you might find something appealing.
-- Dave
70in tall. 8in wide (internal). 11in deep (internal), to which you will need to add the thickness of the material used for the sloping baffle.
Assuming 3/4in material, you will end up with a box externally 9 1/2in wide x 13 1/4in deep. Terminate the internal baffle 5 1/2in equidistant from the internal base, and front & rear walls. Line the front of the internal baffle to just below the height of the driver, and one side-wall to just below the height of the driver (1st half of the line only). Also line the internal base of the cabinet.
Assuming 3/4in material, you will end up with a box externally 9 1/2in wide x 13 1/4in deep. Terminate the internal baffle 5 1/2in equidistant from the internal base, and front & rear walls. Line the front of the internal baffle to just below the height of the driver, and one side-wall to just below the height of the driver (1st half of the line only). Also line the internal base of the cabinet.
Well Rich, it is there.
Though I doubt it is a make or break deal.
I'm of the mind these days that the generic known values for BIB's or any other design don't mean much unless you know for sure what the spec's of your drivers are. The more I've considered what Martin, Scott and others have said in regards to this the more sense it makes. The fact that one can't count on the manufacturer providing this information in a reliable way is frustrating to say the least but apparently it's an issue none the less. I've spent these past few weeks exploring ways to test driver parameters for myself.
Rick
Though I doubt it is a make or break deal.
I'm of the mind these days that the generic known values for BIB's or any other design don't mean much unless you know for sure what the spec's of your drivers are. The more I've considered what Martin, Scott and others have said in regards to this the more sense it makes. The fact that one can't count on the manufacturer providing this information in a reliable way is frustrating to say the least but apparently it's an issue none the less. I've spent these past few weeks exploring ways to test driver parameters for myself.
Rick
"Anyway, after looking at what Home Depot (or where ever) offers, you might want to look in the yellow pages for hardwood dealers. Most of the larger ones sell high quality 'furniture grade' plywood including Baltic birch. You might be shocked at the prices. OTOH, you might find something appealing."
-- Dave
Also you should be able to save some cash by buying shop grade. This will have a few minor flaws here and there but that won't matter if you're going to veneer or paint them.
When considering plywood it's the number of plys that matter not so much the lumber making up the plys. As long as there are no voids within the panels I doubt it matters what species is used.
Dave, I remember the first time I used the metric Russian 1/2" equivalent sheets. It was fine material and made a nice drawer or cabinet back but it made me have to re figure a few things for yield purposes and I didn't like that.
Rick
-- Dave
Also you should be able to save some cash by buying shop grade. This will have a few minor flaws here and there but that won't matter if you're going to veneer or paint them.
When considering plywood it's the number of plys that matter not so much the lumber making up the plys. As long as there are no voids within the panels I doubt it matters what species is used.
Dave, I remember the first time I used the metric Russian 1/2" equivalent sheets. It was fine material and made a nice drawer or cabinet back but it made me have to re figure a few things for yield purposes and I didn't like that.
Rick
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