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

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#2,541
Greets!

For a Fl = 122*0.52/2 = 31.72 Hz flare rate, Leach calcs:

CC = 2.772"^3
St = 1.889"^2
M = 0.542
Sm = 1792.325"^2 for 1/8 space

If the new WS doesn't plot based on flare rate/factor, then use a 256.811" long expo with a Sm = 3584.65"^2 to approximate it. It won't be as flat/well damped, but close enough to get an idea what an ideal BLH is capable of.

GM
 
#2,542
It does, though the simplified sheets are tricker to work with than the sections one IMO (ironic really). Anway, er, here's the calculated response. Oh boy...

Confession time: I never could figure how best to use Leach's math for a regular BLH. Any advice on that Greg? Off topic I know, so perhaps I'd best ask via PM.

Cheers
Scott
 

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#2,544
Even reducing Sm = Fs (983.08"^2), which only reduces length to 212.796", still shows almost as much gain BW, though I imagine much more 'ripple' in the impedance, phase, and excursion plots:
 

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#2,546
The former (using the cut off frequency & M value), still in 1/2 space. I'm a little wary of the newer sheets though -the section one's fine, but I find the others tricky to get singing right. I'll shift to the old sheet & check again. Love that 105 - 110db sensitivity & 35Hz cut off with a 3in driver. 😉 Greg is The Master of The Horn.
 
#2,547
Greets!

I wish!

Hmm, what length did it calc? In half space it should have much more gain around Fc. If the WS doesn't calc the length, then using the expo length will make it too short, screwing up the expansion. Anyway, when a BLH is long/large enough, it's completely reactance annulled and FR, phase, impedance, and excursion are ~flat lined to just above Fc, where it slightly peaks.

GM
 
#2,550
It shall be done. Thanks Greg.

BTW: I've just printed off Leach's paper to take to work with me (teaching today, but they've mostly got practice test papers, so not much 'teaching' involved) & will make an effort to actually work through it & apply to BLHs. Thought I'd warn you in advance, in case I have to ask some daft questions.
 
#2,552
I know GM and Scottmoose put up the design on Zillaspeak, but has anyone had experience with the B200 in a BIB? The response curve looks interesting, especially the gain in midbass over the 168Sig 🙂

I'd assume I'd have to use a helper tweet, but I've got the space, why not go with an 8" BIB 😀
 
#2,553
larkinrulez said:



That's different to the Sm at the BIB-HP...there it is 33 or 49 in^2.
Who tells us the truth...if there is one


😉
Click to expand...


Greets!

'Truth' is in the 'eye of the beholder' and opinions are like a$$holes, everybody's got one:

GM
 

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#2,558
Scottmoose said:
Amen. 😉

FWIW, GM & I have occasionally (frequently?) done different BIBs for the same driver as we take slightly different approaches to designing them. Gives people more of an option really. Either should work well, but they'll sound different.
Click to expand...


Well then, one of them must be "wrong" :clown:

Originally posted by GM

Greets!

'Truth' is in the 'eye of the beholder' and opinions are like a$$holes, everybody's got one:

GM
Click to expand...

My "opinion" speaks to me at least a dozen times a day, rarely any of which is noteworthy (except after the chili :hot: )
 
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