Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 121

Scottmoose · 27th August 2006, 08:01 AM

That's the lowest? Gulp.

Open baffles they shall have to live on then, I fear.

GM · 27th August 2006, 03:14 PM

Greets!

Yeah, the 1044s measured ~1.43 and the 1272 ~2.45! on a P.E. woofer tester.

That said, for an area where looks don't matter and the bass need not be room rattling to please and there's a couple of corners available, David Weems (audio's quintessential 'frugalphile') published some 'one size fits all' single fold labyrinth (now usually referred to either as an end loaded 1/4 WL pipe or TL) designs for different frame size drivers back in the mid '50s issues of Popular Electronics for drivers normally considered unusable in a HIFI app, i.e. high Fs/high Q small console or car audio drivers.

He made them from the then new Celotex 1/2" thick insulation board (~$2.50 for a 4 x 8 ft sheet at the time), an extremely well damped/lossy material, which combined with no additional bracing makes them ideal for super high Q systems. He used a CSA = 1.4*Sd for the first half of the pathlength, 'stepping up' at the fold to ~1.65*Sd for the other half, but we know today that 'bigger is better', so make it as large as practical with a pathlength = ~72" so that when combined with the corner it will give fairly broadband LF damping (relatively speaking) and if the driver's Fs is low enough to make it 'boom', then an aperiodic vent can be added to tame it.

We have many more material choices today though, so let your imagination run amuck like one poster did awhile back.

He mounted the driver on a typical box width OB, then covered it/boxed it in with styrofoam? insulation sheeting for a free standing speaker.

GM

pjanda1 · 27th August 2006, 04:53 PM

Hi guys, it's been awhile!

My local Menards (upper midwestern big crappy building supply store) just started carrying 4x8 sheets of 3/4" Baltic Birch for $60. I was about to buy four sheets a build up some BIB's for my hemps. Then I got a gig working around 80 hours a week for a campaign. The good news is, come November, I'll be unemployed and have some $$ for plywood. In the mean time, the hemps sound awfully good as is.

Back in the neighborhood of page 22, GM conjurred a ML BIB for the Ascendant Audio Assassin 10 sub (double the CSA of the orignal TC design, but with an 8x8" vent). I can't remember where I put the chart he sent me, but I think it's worth inclusion in the BIB bass horn page, as the work is already done.

Paul

Scottmoose · 27th August 2006, 05:04 PM

Yes indeed. I forgot about that one (it's a few pages ago!) but well worth including, as you'd expect, coming from the source.

GM · 27th August 2006, 05:28 PM

Quote:

Originally posted by pjanda1
My local Menards (upper midwestern big crappy building supply store) just started carrying 4x8 sheets of 3/4" Baltic Birch for $60.

Greets!

Hmm, I can't help but wonder if it's the 'real deal' grade wise since AFAIK the top grade 13 ply we want only ships in 150 cm square sheets per Russian export standards, though there are numerous lower grades that conform to our building codes. Not to mention the relatively cheap price since the square sheets cost more than this locally.

My SWAG is they're offering furniture grade at best (A/B, or more likely, B/B), which can have putty filled knots, internal splits, etc., which can potentially wreak havoc in a speaker app, so Caveat Emptor.

GM

Scottmoose · 27th August 2006, 05:44 PM

No wonder I usually stick with MDF, for all it's problems...

loninappleton · 27th August 2006, 08:37 PM

Quote:

Originally posted by GM

Greets!

Hmm, I can't help but wonder if it's the 'real deal' grade wise since AFAIK the top grade 13 ply we want only ships in 150 cm square sheets per Russian export standards, though there are numerous lower grades that conform to our building codes. Not to mention the relatively cheap price since the square sheets cost more than this locally.

My SWAG is they're offering furniture grade at best (A/B, or more likely, B/B), which can have putty filled knots, internal splits, etc., which can potentially wreak havoc in a speaker app, so Caveat Emptor.

GM

I go to the Menards all the time. I'd say that their Birch
plywood would be a good deal at $40/sheet or less. One
deal I missed was plywood with birch one side and maple the
other for $30 or so at the Menards (Appleton branch.)

loninappleton · 27th August 2006, 08:45 PM

Quote:

Originally posted by pjanda1
Hi guys, it's been awhile!

My local Menards (upper midwestern big crappy building supply store) just started carrying 4x8 sheets of 3/4" Baltic Birch for $60. I was about to buy four sheets a build up some BIB's for my hemps. Then I got a gig working around 80 hours a week for a campaign. The good news is, come November, I'll be unemployed and have some $$ for plywood. In the mean time, the hemps sound awfully good as is.

Back in the neighborhood of page 22, GM conjurred a ML BIB for the Ascendant Audio Assassin 10 sub (double the CSA of the orignal TC design, but with an 8x8" vent). I can't remember where I put the chart he sent me, but I think it's worth inclusion in the BIB bass horn page, as the work is already done.

Paul

I'll give the 'me too' for the inclusion of the Assassin in the
BIB's for basshorn. It looks to me my pick if I ever go sub.

OT: can the Assassins run with one of those inexpensive MCM
or PE sub amps? I have a jack out of a Yamaha RP U100 to
connect a sub. 'Got no idea what it would do.

planet10 · 27th August 2006, 08:52 PM

Quote:

Originally posted by Scottmoose
No wonder I usually stick with MDF, for all it's problems...

MDF -- still not worth it...

We get a 5x5' sheet of 18mm BB for <$50 CAD (we most often use even less expensive 12 & 15mm)

dave

Scottmoose · 27th August 2006, 09:09 PM

I spoke with some levity. But I wish it were like that in the North East of the UK. A medicore sheet of 18mm birch ply riddled with voids, sets us back £36.95 from B&Q. It's not sold by them in thinner sheets, though we do have the option of 3 or 5 ply spruce, with even more voids, for about £25, which is only useful for boarding up smashed shop windows. It's very low quality stuff.

Void free is not sold at all in my area, nor do I know of anywhere that will deliver it -most suppliers only deliver within a set radius, and there aren't any near me. Those that do stock it elsewhere seem to be under the impression that £70 a sheet is good value too.

That's why I use MDF. Not great, but sensibly priced, and I'd rather have a sheet of that than a sheet of something of duff quality that costs 3 times as much.

27th August 2006, 03:14 PM	#1202
GM diyAudio Member Join Date: Jun 2003 Location: Chamblee, Ga.	Greets! Yeah, the 1044s measured ~1.43 and the 1272 ~2.45! on a P.E. woofer tester. That said, for an area where looks don't matter and the bass need not be room rattling to please and there's a couple of corners available, David Weems (audio's quintessential 'frugalphile') published some 'one size fits all' single fold labyrinth (now usually referred to either as an end loaded 1/4 WL pipe or TL) designs for different frame size drivers back in the mid '50s issues of Popular Electronics for drivers normally considered unusable in a HIFI app, i.e. high Fs/high Q small console or car audio drivers. He made them from the then new Celotex 1/2" thick insulation board (~$2.50 for a 4 x 8 ft sheet at the time), an extremely well damped/lossy material, which combined with no additional bracing makes them ideal for super high Q systems. He used a CSA = 1.4Sd for the first half of the pathlength, 'stepping up' at the fold to ~1.65Sd for the other half, but we know today that 'bigger is better', so make it as large as practical with a pathlength = ~72" so that when combined with the corner it will give fairly broadband LF damping (relatively speaking) and if the driver's Fs is low enough to make it 'boom', then an aperiodic vent can be added to tame it. We have many more material choices today though, so let your imagination run amuck like one poster did awhile back. He mounted the driver on a typical box width OB, then covered it/boxed it in with styrofoam? insulation sheeting for a free standing speaker. GM __________________ Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

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27th August 2006, 08:01 AM	#1201
Scottmoose diyAudio Member Join Date: Mar 2005 Location: UK	That's the lowest? Gulp. Open baffles they shall have to live on then, I fear.

27th August 2006, 04:53 PM	#1203
pjanda1 diyAudio Member Join Date: Jan 2005 Location: Boulder, CO	Hi guys, it's been awhile! My local Menards (upper midwestern big crappy building supply store) just started carrying 4x8 sheets of 3/4" Baltic Birch for $60. I was about to buy four sheets a build up some BIB's for my hemps. Then I got a gig working around 80 hours a week for a campaign. The good news is, come November, I'll be unemployed and have some $$ for plywood. In the mean time, the hemps sound awfully good as is. Back in the neighborhood of page 22, GM conjurred a ML BIB for the Ascendant Audio Assassin 10 sub (double the CSA of the orignal TC design, but with an 8x8" vent). I can't remember where I put the chart he sent me, but I think it's worth inclusion in the BIB bass horn page, as the work is already done. Paul

27th August 2006, 05:04 PM	#1204
Scottmoose diyAudio Member Join Date: Mar 2005 Location: UK	Yes indeed. I forgot about that one (it's a few pages ago!) but well worth including, as you'd expect, coming from the source.

27th August 2006, 05:44 PM	#1206
Scottmoose diyAudio Member Join Date: Mar 2005 Location: UK	No wonder I usually stick with MDF, for all it's problems...

27th August 2006, 09:09 PM	#1210
Scottmoose diyAudio Member Join Date: Mar 2005 Location: UK	I spoke with some levity. But I wish it were like that in the North East of the UK. A medicore sheet of 18mm birch ply riddled with voids, sets us back £36.95 from B&Q. It's not sold by them in thinner sheets, though we do have the option of 3 or 5 ply spruce, with even more voids, for about £25, which is only useful for boarding up smashed shop windows. It's very low quality stuff. Void free is not sold at all in my area, nor do I know of anywhere that will deliver it -most suppliers only deliver within a set radius, and there aren't any near me. Those that do stock it elsewhere seem to be under the impression that £70 a sheet is good value too. That's why I use MDF. Not great, but sensibly priced, and I'd rather have a sheet of that than a sheet of something of duff quality that costs 3 times as much.