Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 123 - diyAudio
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Old 29th August 2006, 10:42 PM   #1221
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I have to ask.....

Can these bib's be loaded with dual drivers (as a compound driver or 2 individual drivers) and if so what happens with the results?

Can one driver be used to help alleviate the ripple for a more streamlined sim?

thanks for humoring me


Andrew
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Old 30th August 2006, 12:16 AM   #1222
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Greets!

Sure! Dual drivers will be up to 6 dB louder and require 2x the pipe Vb, while compound drivers will dramatically reduce the required pipe Vb, which is only a 'good thing' with drivers that require huge cabs. Also, due to depth limitations they will have to be clamhell mounted, relegating them to sub duty.

Yes, though its placement will make it impractical AFAIK unless mounted internally like Danley Soundlab's Tower Of Power sub.

GM
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Old 30th August 2006, 02:05 AM   #1223
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Talking of dual drivers I have a set of drivers/crossovers for a pair of Ariels (MTM) sitting around and was thinking of puting them in a BIB. I had assumed from what I had read that means doubling the mouth area to effetively double the volume to allow for the Vas being doubled. Length would stay the same for that driver??

Regards driver position, distance from top of cab - would you use the mid point between the drivers?

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Old 30th August 2006, 02:23 AM   #1224
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Thanks Gm,

You're answers were what I thought to myself but I was not sure which is why I rather ask and hear (read) from those like yourself who know. So with the driver configuration changes, a BIB pretty much responds in a similar fashion as a BR.

Andrew
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Old 30th August 2006, 06:32 AM   #1225
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Calling Jim......... How big did your box actually end up?

I've been working out the dimensions to make best use of the sheets, and after calculating

the height am a bit intimidated by the size of these things... exterior dims: 12.8"W x

20.25"D x 82.7"H javascript:smilie('') [allowing for a base in proportion].

The height of my ceilings is only 94.5". As the walls and ceiling form the mouth of the horn,

is there enough space for this to work properly?

Way back somewhere in this thread I thought it was decided that cab height was half line

length [or at least pretty close]. But thinking back it may have been more a rule of thumb

for smaller drivers.

I've managed to keep the internal ratio to 1.414, and will increase the front and rear baffle

thickness to 25mm [1"]. Are any braces needed in there, or does the internal baffle suffice?

This is a big box! Just need to know if it's too close to the ceiling.

Thanks again, John.
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Old 30th August 2006, 07:56 AM   #1226
McFaBs is offline McFaBs  Italy
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Quote:
Originally posted by copperhead
Calling Jim......... How big did your box actually end up?

I've been working out the dimensions to make best use of the sheets, and after calculating

the height am a bit intimidated by the size of these things... exterior dims: 12.8"W x

20.25"D x 82.7"H javascript:smilie('') [allowing for a base in proportion].

The height of my ceilings is only 94.5". As the walls and ceiling form the mouth of the horn,

is there enough space for this to work properly?

Way back somewhere in this thread I thought it was decided that cab height was half line

length [or at least pretty close]. But thinking back it may have been more a rule of thumb

for smaller drivers.

I've managed to keep the internal ratio to 1.414, and will increase the front and rear baffle

thickness to 25mm [1"]. Are any braces needed in there, or does the internal baffle suffice?

This is a big box! Just need to know if it's too close to the ceiling.

Thanks again, John.
Hi John, I'n not an expert, But where did you get 82,2" H for Hemp?
Considering the Dims on Zilla site, if you use
L= 150.5
Sm = 200"^
So = 30.1
my results considering GM and Scottmoose suggestion are:
D = 17.25" (a bit more deep) int.
W= 11.55" int.
H= 77.1" int. (considering semicircle lenght)
H external = 78.1
So = 30.74
You can also try GM dims
L= 140
Sm= 303"^
So =30
and I got
D= 21" int
W=14.45" int
H = 72.26"
H external 73.26"
So= 30

Maybe GM could explain well the maximum distance from the ceiling and its interaction. But I think you can play with the position from corners and rear walls to balance the response. Anyway, having the mouth closer to the ceiling it's more or less like an inverted BIB using the floor....

Ciao.Fab
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Old 30th August 2006, 08:15 AM   #1227
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Well, I did say they'd be a little large... The line length is not exactly length /2, but that gets you close enough, though there's an excellent spreadsheet available on the thread & elsewhere that makes a good partner to Greg's that helps you calc the exact cabinet height for a given line length.

Chris -funny you should mention an Ariel BIB. I did a cabinet for these a while back, but I can't find it anymore, so I re-ran the sim:

Line length 112in
Zdriver 24.5in
Sm=64.0625in^2
Attached Images
File Type: gif ariel bib.gif (6.4 KB, 420 views)
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Old 30th August 2006, 08:26 AM   #1228
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Hi Fab,

The internal height of the cab I calculated as 80" [if line length is a path bisecting the front and

internal baffles, a semi-circle around the bottom of the internal baffle, plus the thickness of that

baffle, then upward, bisecting internal and rear baffles.]

I included a 3/4'' base that would be included inside of the cab, [if that makes sense, that would

be temporarily screwed in place as per Scotts' recommendation], and then that whole thing

sitting on a 2" granite or marble base.

I don't think I screwed up the measurements.

John.
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Old 30th August 2006, 09:01 AM   #1229
McFaBs is offline McFaBs  Italy
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Quote:
Originally posted by copperhead
Hi Fab,

The internal height of the cab I calculated as 80" [if line length is a path bisecting the front and

internal baffles, a semi-circle around the bottom of the internal baffle, plus the thickness of that

baffle, then upward, bisecting internal and rear baffles.]

I included a 3/4'' base that would be included inside of the cab, [if that makes sense, that would

be temporarily screwed in place as per Scotts' recommendation], and then that whole thing

sitting on a 2" granite or marble base.

I don't think I screwed up the measurements.

John.

Hi John,
I don't know.... I'm putting on paper my BIB, but before that, I've tried to draw the dims straight on the plywood 1:1 scale to measure and check the dimensions. Start with L/2 and placed the internal baffle with different thickness wood, I measured very little difference between the oblique line and the straight one (not even 5mm!). Then I considered the semicircle path and made the adjustment...
So I consider 80" internal much longer than it should be....

It make sense that your speakers rise up using the marble bases, but be aware of marble and similar, in my experience when I tried granite and marble under my turntable, the sound got worse! And it was possible to hear different sound from different marbles. So I turn ed to thick plywood instead, as long as a friend of mine made some astonishing platforms.

Cheers.
Ciao. Fab.
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Old 30th August 2006, 10:43 AM   #1230
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Hi Fab,

I got an internal depth of 17.58", internal baffle 8.79" from front back and base.

The internal baffle came out to 71.44" long. Your right the oblique angle is only a fraction

longer. 71.3" + 8.79" = 80.09". I was going for a heavier base on Scotts' suggestion.

I don't have any experience of marble or granite but it had seemed like a good idea.

Plywood is easier and cheaper.

John.
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