The Locust I - Page 3 - diyAudio
 The Locust I
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
diyAudio Member

Join Date: Jul 2003
Location: Silicon Valley
Quote:
 Originally posted by GM nothing ventured, nothing gained. GM
I did put an equation into the worksheet to re-calculate Qts, but I got a different number, so I'll check my formula.

[Added a few minutes later] Actually, I just copied the formula from a worksheet on Martin's web page. The worksheet is for the Fostex fe206e. (Of course I changed the original Q to the one for the fe107e.)
Here is the formula:

Qed' := Qed*(Re)*(Re-Rs)**-1

Is that right?

I'm probably already reaching the limit of what those little drivers can do, even in a small room. For a given SPL, cone excursion quadruples every octave, right? And the xmax on those is tiny. Still, I'll play around some more.

Dave

"Nothing vented nothing gained."
__________________
Davy Jones

diyAudio Member

Join Date: Jul 2003
Location: Silicon Valley
I think I have the Qes figured right now, and I put in the numbers exactly as you said. Here's the function, assuming a total added resistance of 5 Ohms:
Attached Images
 spl.png (3.9 KB, 527 views)
__________________
Davy Jones

 20th June 2004, 09:00 PM #23 diyAudio Member     Join Date: Jun 2003 Location: Chamblee, Ga. >For a given SPL, cone excursion quadruples every octave, right? ==== Correct. ==== >And the xmax on those is tiny. Still, I'll play around some more. ==== Yeah, and I don't know how much excursion it has before either popping out of the gap and hanging, or bottoming out. For sure I wouldn't drive it past 1/8" until you find out what Xsus/Xmech is. ==== >I think I have the Qes figured right now, and I put in the numbers exactly as you said. Here's the function, assuming a total added resistance of 5 Ohms: ==== Hmm, don't know what you're doing, but you're not getting the right response. Notice that the IB response hasn't flattened out so it's not plotting the higher Qts response, ergo the higher Q vented response. GM __________________ Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
diyAudio Member

Join Date: Jul 2003
Location: Silicon Valley
Quote:
 Originally posted by GM Hmm, don't know what you're doing, but you're not getting the right response. Notice that the IB response hasn't flattened out so it's not plotting the higher Qts response, ergo the higher Q vented response. GM
It actually is flattened out a little bit, but very little. I'm probably not calculating the new Qes correctly. See the attachment.
__________________
Davy Jones

diyAudio Member

Join Date: Jul 2003
Location: Silicon Valley
Quote:
 Originally posted by Dave Jones It actually is flattened out a little bit, but very little. I'm probably not calculating the new Qes correctly. See the attachment.
Attached Images
 gm added res.png (10.1 KB, 542 views)
__________________
Davy Jones

diyAudio Member

Join Date: Jul 2003
Location: Silicon Valley
Okay, it's better now.

Sometimes MathCad 2000 starts refusing to update the graphs for me. If I save the file and re-load it, everything is cool again.

Does this chart look better?
Attached Images
 better.png (3.7 KB, 455 views)
__________________
Davy Jones

 21st June 2004, 12:02 AM #27 diyAudio Member     Join Date: Jun 2003 Location: Chamblee, Ga. Yep, now it looks like mine. I have the same problem with Mathcad too, but I just assumed it was my machine since it's so outdated 'n slow. GM __________________ Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
diyAudio Member

Join Date: Jul 2003
Location: Silicon Valley
Quote:
 Originally posted by GM Yep, now it looks like mine. I have the same problem with Mathcad too, but I just assumed it was my machine since it's so outdated 'n slow. GM
MathCad does not impress me. But Martin's worksheets do.
__________________
Davy Jones

diyAudio Member

Join Date: Jul 2003
Location: Silicon Valley
Quote:
 Originally posted by GM BTW, why didn't you parallel the bypass cap around all the resistance? GM
I tried it both ways. I liked it better across only the 4 Ohm. ... a little less treble boost than BSC boost. There's not a big difference of course.
__________________
Davy Jones

 21st June 2004, 12:55 AM #30 diyAudio Member     Join Date: Jun 2003 Location: Chamblee, Ga. Fair enough. Not having heard this driver, I was just curious. Yeah, they impress me too. I've been designing tower speakers (now ML-TL) since the late '60s, but no formula I could ever find would accurately predict vent length, and not having the math skills to wade through all the gas law formulas I never could come up with any calc or even rule-of-thumb to figure it. And of course stuffing was trial n' error. GM __________________ Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 New To Site? Need Help?

All times are GMT. The time now is 02:27 AM.