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

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#5,541
Thanks again GM!

I got a bit confused with the sims and I just realized that I forgot to change the zdriver in the calculator. 😱

I think I will try out the Faital driver in the smaller downfiriing cabs that I already have cut, but with zdriver at 0,42 or 0,5 as in the first drawings i posted. I assume the sims are with the driver at the 0,216 position I mistakenly had?

As for the fe108es, as we're getting close to the size of my already made FF165k BIBs I may just throw them in and add some extra stuffing to see what's what. The cabs have a Sm of approx 95 sq. in.

An externally hosted image should be here but it was not working when we last tested it.


I have a second pair and could try doubling them up.

An externally hosted image should be here but it was not working when we last tested it.



GM said:
Don't feel like the Lone Ranger 😉, wanting multiple alignments in a single message tends to do that; so with me doing any responses, sims in little spurts [during TV commercials, phone calls, doing chores, etc, and late at night] combined with failing memory and only HR loaded, I have to keep rereading/checking to hopefully make sure I'm getting it all right.

Regardless, I was working on this request, which I thought was the real goal if it was a realistic one to build:



Unfolded, it ideally needs to be longer than 8 ft, but the F2 makes it large enough to handle some pretty significant bass in stereo even if there's not much room gain. For sure it theoretically will freak folks out that a large tweeter can make bass like a really large woofer with the same area [Sd] as the pipe horn's terminus [Sm].

This doesn't mean it will hit high SPLs though since it will only be able to 'cleanly' handle a fraction of a watt down low, but cab efficiency will be high, so a pair theoretically should peak in the 95-100 dB/m range down to at least 40 Hz or a little more if these drivers can be overdriven a bit without making them sound obviously distorted in the critical mids.

In short, the bigger we can make [Sm], the better. Ditto length, so was thinking about a detachable 'top hat' to extend it closer to the ceiling.

No, this is a comparison of the same BIB with the red trace being yours with its default 0.217 driver offset and the gray is at 0.42.

Closed pipes such as a TL, conical horn are basically two octave devices with its first dip at the 3rd harmonic, so if it's tuned to 20 Hz, then the dip is around 80 Hz, etc., ergo as the driver location is shifted away from its closed end, its harmonic structure is changed and the higher it's shifted, the less damping usually required plus the less chance any room modes will aggravate the problem.

GM
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#5,542
You're welcome!

Hmm, actually, I just noticed that this version of the calculator [there's been several] doesn't have the 0.42 calculation and no way to change it, but simple enough to calculate it yourself: Zdriver = line length [L]*0.42

GM
 
#5,544
Hi
I'm going to attempt my first speaker build very soon, and have decided to start with a BIB 🙂 I quite like the Alpair drivers - but some newbie questions if I may....
The Alpair 10M (fr 38.27 vas 26.32 qts .316) using the calc it gives me a 228cm tall enclosure, which is approx 14cm below my ceiling! Is this too close?? Anyone else tried them?
The other driver is the Alpair 7 (fr 70.9 vas 4.58 qts .54) which the calc makes it only 125cm tall - so too far from ceiling?? Again anyone else using them...?
Any advice / tips gratefully received 🙂
Thanks
Tony
 
#5,545
After spending the last couple of years building open baffle projects I can really appreciate the simplicity of BIBs! Single driver, tune with stuffing, corner placement and enjoy!
 

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#5,546
bristto said:
Hi
I'm going to attempt my first speaker build very soon, and have decided to start with a BIB 🙂 I quite like the Alpair drivers - but some newbie questions if I may....
The Alpair 10M (fr 38.27 vas 26.32 qts .316) using the calc it gives me a 228cm tall enclosure, which is approx 14cm below my ceiling! Is this too close?? Anyone else tried them?
The other driver is the Alpair 7 (fr 70.9 vas 4.58 qts .54) which the calc makes it only 125cm tall - so too far from ceiling?? Again anyone else using them...?
Any advice / tips gratefully received 🙂
Thanks
Tony
Click to expand...

For the Alpair 10M one, IMO 14 cm is close to the ceiling but not too much. IIRC, 20-30 cm is the ideal distance. Check the resulting driver height to ensure it is within a manageable range. And also check with your other important half because it seems it can be a true beast with low WAF. 🙂
If the height is too much you can try with a triple folded BIB but it kind of kills the simplicity of the original design.

OTOH, more than 90 cm is too far away to work. For the Alpair 7 you should try the iBIB (Inverted BIB, the name says it all) which could be a compromise between performance and driver height.
 
#5,547
Tony,
Based on my experience I think you will be ok with the 14cm gap to the ceiling. Somewhere in this thread GM gives a formula for gap to the ceiling based on area of the vent. On my bib with fostex 166en drivers I believe the math indicated a gap of ~4 inches. I ended up with a 12 inch gap, but that is because of the materials I had. Meaning I have 9 foot ceilings and I made my boxes out of 4 foot x 8 foot plywood.

Plan b if you don't like the bib is the inverted bib and then you can play with the gap at the floor.

Most helpful advice. How you stuff the point can really affect the sound. If you don't love it at first tune the speaker by stuffing the point. Good luck. It can be a great sounding but easy speaker.
 
#5,549
bristto said:
Hi
I'm going to attempt my first speaker build very soon, and have decided to start with a BIB 🙂 I quite like the Alpair drivers - but some newbie questions if I may....
The Alpair 10M (fr 38.27 vas 26.32 qts .316) using the calc it gives me a 228cm tall enclosure, which is approx 14cm below my ceiling! Is this too close?? Anyone else tried them?
The other driver is the Alpair 7 (fr 70.9 vas 4.58 qts .54) which the calc makes it only 125cm tall - so too far from ceiling?? Again anyone else using them...?
Any advice / tips gratefully received 🙂
Thanks
Tony
Click to expand...

Greets!

No, none of the drivers popular on any of the DIYaudio forums.

Here's a guideline I posted awhile back for floor, ceiling gap, so what does it calculate?: http://www.diyaudio.com/forums/full...e-fostex-craft-handbooks-110.html#post4903502

If too close, the sides of the terminus can be notched out to spread the loading along the ceiling wall seam and if too far away, a simple rectangular tube [or flared for increased loading] 'top hat' can be added to fine tune any BIB.

Note too that pipe horns are very flexible alignments, so one can use specs different from the drivers one has to get a pipe that fits the room/available 'footprint'/whatever as long as its tuning is no lower than [Fs*Qts/2] or higher than [2*Fs/Qts], though never having experimented with such extreme alignments, don't know how well they would perform, especially with smaller, low power handling drivers.

For sure, they will need to be up against a wall [1pi loading] and probably increasingly need corner loading [0.5pi] the further below Fs it's tuned.

Of course, if the cab has less net volume [Vb] than the 'optimum' alignment, then there will be less bass gain bandwidth [BW] regardless of tuning.

GM
 
#5,550
Tony- FWIW there are several well proven designs for the two Alpair drivers listed that are as easy to build as a BIB, and something that is a very important factor for some folks - a smaller enclosure / footprint.

Brines' M10A10 and Scott's Pensil for A10.3
M10-A10
http://frugal-phile.com/boxlib/pensils/Pensil103-plan-300114.pdf

Pensil for A7.3 http://frugal-phile.com/boxlib/pensils/Pensil7s3-map.pdf

I've never built a BIB, and have only heard two over a dozen years ago Terry's original as shown at VSAC in 2001, and FE108E Sigma by DaveCan . I'm one of those guys for whom size can be an impediment.

make your own joke
 
#5,552
IME, there would be no comparison per se since the BIB will 'control'/modulate the driver much more, especially in the critical lower vocals BW, so it will boil down to the room's impact on each's performance and personal preferences and IME with similar vented [ML] pipe horns, folks with large rooms and/or long listening distances will prefer the BIB/BLH and the rest the smaller cabs, which don't sound so 'throaty'/'chesty'/'in your face'.

GM
 
#5,553
It's finally in one piece, after these pictures, I added more damping material on the panels etc. I'm erecting my version of Stonehenge tomorrow. Oh, but I have to drill the bottom hatch first. And saw a double-layered baffle. It's those damn little things, isn't it? 🙂

The wife is a bit anxious. "You are getting rid of the smaller ones, right? You get to build two of these, but you get rid of the smaller ones! And can we watch Independence Day when this one is done?"

😉
 

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#5,554
Sweet! 😀 I want to see more of the room, house; ya'll folks in that area of the world have the most fabulous looking wood and most? don't hide it with dark stain like in my locale.

I forget, what are the mains? I presume she means getting rid of the TB BIBs?

GM
 
#5,555
GM said:
Sweet! 😀 I want to see more of the room, house; ya'll folks in that area of the world have the most fabulous looking wood and most? don't hide it with dark stain like in my locale.

I forget, what are the mains? I presume she means getting rid of the TB BIBs?

GM
Click to expand...

Apart from the oak floor (it's actually laminate with real oak veneer instead of woodprint plastic), not much wood exposed in the living room. We have a more modern taste, modest budget and a toddler that dictates scratch resistant finish.

The exterior of the house is all brick, structure is concrete. We call it our nuclear bunker, we have bad wifi and cellphone coverage etc. Seems perfect for cornerhorns and I want to build the Olson corner horn at some point. A Dutch diy hifi guy made a 3D model of the original drawings, in time these must become a cut sheet.

The current BiBs are the little ones with the mini-arrays. I already got rid of the TB-BiB to make space.
 
#5,557
Ivo said:
We have a more modern taste, modest budget and a toddler that dictates scratch resistant finish.

I want to build the Olson corner horn at some point. A Dutch diy hifi guy made a 3D model of the original drawings, in time these must become a cut sheet.
Click to expand...

Copy that! Been there, done that, several times, now starting on great grandkids. 😱

What wood [laminate?] are the [presumed] line arrays on either side of the white panels?

Ooh! Had the pleasure to audition one back before I understood how technically special it was beyond being measured ~flat down to 20 Hz in room at a time when a recording's useful BW ended around 80 Hz.

Will these be made public with/without a fee?

GM
 
#5,559
GM said:
Copy that! Been there, done that, several times, now starting on great grandkids. 😱

What wood [laminate?] are the [presumed] line arrays on either side of the white panels?

Ooh! Had the pleasure to audition one back before I understood how technically special it was beyond being measured ~flat down to 20 Hz in room at a time when a recording's useful BW ended around 80 Hz.

Will these be made public with/without a fee?

GM
Click to expand...

Great grandkids... My toddler is three, I can't picture her as a grandma yet...

Yeah, those are the line array BiBs, those are untreated pinewood.

The drawings of the Olson horn are from the audio asylum, Bill Woods perhaps? Anyway, I used those to make a 3D model in Sketchup but got stuck. Someone on my Dutch forum is very good with that stuff and made a good model. Nothing secret as far as I'm concerned and not my property. The model is accessible on the Dutch forum, I'll check if the maker agrees with sharing it here. It's not a detailed plan or a cutsheet yet, though.
 
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