Problem with BIB-165K sim

[zek]

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?

 

[zek]

..and the shortened one...

 

[Scottmoose]

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.

 

[GM]

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

 

[zek]

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.

 

[GM]

You're welcome! With its high Vas, low Qts, it needs a matching impedance amp to 'sing':

GM

 

[zek]

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.

 

[GM]

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

 

[zek]

Thanks Greg.

 

[Godzilla]

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.

 

[GM]

Yeah, it just has a little more tuning flexibility. Indeed, might as well just use TC's 'stock' height/driver location:

L = ~138"
Sm = ~113.873"^2 (~8.973" W x 12.69" D)
a-b-c = ~6.345"
zdriver = ~29.949"

GM

 

[Scottmoose]

Sorry guys & particularly Greg. I thought there was something wrong, but I didn't have time to look into it this morning, as I needed to get over to Salford to meet some Pakistani naval commanders. Glad it's sorted out though. The 165 really does have a bit of magic in this load, despite the limited Xmax. Not one for belting out Iron Maiden, but if you like acoustic music in particular, you're laughing.

 

[GM]

Greets!

Understood, so no need, I wasn't trying to lay a guilt 'trip' on you, though I was a bit surprised no one had taken me to task. Infallible I'm not.

GM

 

[ronc]

Infallible I'm not.


If i ddint goof up at least once a day, i didnt show up for work.

ron

Pakistani naval commanders

Isint that an oxymoron?

 

[GM]

I resemble that remark!

Now-now, I had to bite my hand to keep from typing that!

 

[seanzozo]

http://en.wikipedia.org/wiki/Pakistan_Navy

 

[Scottmoose]

Now now...

(OK, not quite the USN, or even the RN. But they've got a pretty good record -they're not a blue-water force at present, though that might change slowly over the next couple of decades.).

God knows I make enough mistakes. I'd worry if I didn't. Blame the computer Greg. It's what I do.