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Old 16th December 2007, 09:04 PM   #1
zek is offline zek  Serbia
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Question Problem with BIB-165K sim

I'm working on BIB Fostex FF165K sim, but I have some problems, or missuderstanding.
When I put T/S data into BIB_166_GM_v2 sheat , I get L=168,31 in. and Sm=93.50 sq.in. (more that on Zilla site - Sm=88.125 sq.in.)
If I shorten L and change Fr to 50Hz, then Sm become bigger (Sm=116.87 sq.in.)
What I'm doing wrong?
How to calculate shorter pipe?
I think that Sm must be the same - not bigger if pipe L shorten?
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Old 16th December 2007, 09:07 PM   #2
zek is offline zek  Serbia
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..and the shortened one...
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File Type: png bib_165k_short.png (11.7 KB, 208 views)
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Old 16th December 2007, 09:16 PM   #3
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You're doing nothing wrong. As noted elsewhere, most of the Zilla dimensions pre-date the math used in the spreadsheet by many months, and are obsolescent, if not obsolete. They'll work OK; the dimensions provided by the spreadsheets will work better however.
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Old 16th December 2007, 09:19 PM   #4
GM is offline GM  United States
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Greets!

It takes 'x' amount of net volume (Vb) per Hz of gain BW and when you shorten it you're reducing Vb, so the wall angle and base area must increase to offset the loss in pipe loading. IOW no matter what Fp you choose, the net Vb stays the same whether tall and narrow or short and wide, though there's a point at both extremes where the simple math returns an unacceptably performing alignment.

GM
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Old 16th December 2007, 09:42 PM   #5
zek is offline zek  Serbia
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Thank you Scott and GM for yours answers.
Will you be so kind to do frequency sim for my shorten pipe, because I have some trouble with MJK work sheet.
Thanks in advance.
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Old 17th December 2007, 05:20 AM   #6
GM is offline GM  United States
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You're welcome! With its high Vas, low Qts, it needs a matching impedance amp to 'sing':

GM
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File Type: gif ff165k t.c. bib 25 hz fp.gif (8.2 KB, 190 views)
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Old 17th December 2007, 09:23 AM   #7
zek is offline zek  Serbia
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Hi Greg,
I'm realy surprised with the graph you attached, because it is so different to the graph on Zilla site.
It seems that this driver is not a good candidate for BIB enclosure.
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Old 17th December 2007, 02:22 PM   #8
GM is offline GM  United States
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Greets!

I was too and frankly knew that I'd screwed up, but due to a variety of factors beyond my control at the time I couldn't find it, so posted it anyway figuring Scott would review/correct as required since he gets up in an earlier time zone, but he didn't.

Anyway, I found my multiple inputting errors:

GM
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File Type: gif ff165k t.c. bib 25 hz fp.gif (8.0 KB, 158 views)
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Old 17th December 2007, 02:42 PM   #9
zek is offline zek  Serbia
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Thanks Greg.
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Old 17th December 2007, 02:46 PM   #10
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The 169" Line is very close to the new math with Sm of 93 compared to 88 sq/inch. Regardless of the measurements the 165k is a very fine sounding driver in a BIB.
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