ported box design question: is exceeding the Vas of the driver bad? - diyAudio
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Old 15th March 2003, 04:43 AM   #1
BrianGT is offline BrianGT  United States
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Default ported box design question: is exceeding the Vas of the driver bad?

I recently purchased a pair of Raven R2 tweeters, and Cabasse 21m18LB3/8 woofers from another member of the forum (thanks a lot, TimB), and am thinking about making a pair of speakers with them similar to the orca design on zalytron:

crossover:
http://www.zalytron.com/Schematics/990703_a.jpg
cabinet:
http://www.zalytron.com/Schematics/990703_b.jpg

The Vas of the driver is 53L, and the reference cabinet design is 53L. I have done some simulations with MJK's (www.quarter-wave.com) ported box worksheets, and the cabinet doesn't seem optimal. If I double the depth of cabinet, then I get a much better response. I have attached the image below.

Is having a cabinet size double the Vas of the driver bad practice? I noticed that on TL enclosures, this is often the case, if not more then 2x.

One more thing, if I change the box size, and keep the front baffle dimensions and driver placement the same, can I keep the same crossover?

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Brian
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Old 15th March 2003, 04:47 AM   #2
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www.diyaudio.com > bass reflex > EBS

:-D
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Old 15th March 2003, 04:49 AM   #3
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Arrow Let me correct that link

let me correct that link!

www.diysubwoofers.org ! >ported > EBS

thats better!
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Old 15th March 2003, 05:03 AM   #4
BrianGT is offline BrianGT  United States
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Default Re: Let me correct that link

Quote:
Originally posted by mikee12345

www.diysubwoofers.org ! >ported > EBS
Thanks for the link. It looks like I created an ebs cabinet without knowing what it was

Are there any real drawbacks to this design modification? I measured the impedence curves of the drivers in lab today, and I will do the calculations later to see how close the drivers match the published spec.

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Brian
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Old 15th March 2003, 06:11 AM   #5
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it means that possibly u may get a peak at resonance
pershaps some high group delay also at the peak..

www.linearteam.dk
try that


ive never built an EBS

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Old 15th March 2003, 05:56 PM   #6
Variac is offline Variac  United States
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I've seen lots of mentions that room gain bumps up the lower part of the curve, so maybe flat isn't what you want. Where does the room gain begin? Pprobably depends on the room and speaker placement.
Here's a link to a thread:


Room Gain
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Old 15th March 2003, 06:11 PM   #7
herm is offline herm  United States
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Brian,

I am getting a different response than you are.
Here's my plot using WIN ISD (see link in Mikee's post)

Am I using the program wrong?

Green is 52.5 liter, Blue is 105 liter

Click the image to open in full size.
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Old 15th March 2003, 06:24 PM   #8
BrianGT is offline BrianGT  United States
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I have posted my results from the mathcad in html format, and you can view them here:
http://brian.prohosting.com/21m18/

I will go download WinISD and see what I get with it.

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Old 15th March 2003, 06:37 PM   #9
BrianGT is offline BrianGT  United States
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I get a fairly similar result with WinISD... check this out:

It doesn't seem to account for stuffing, or exact dimensions of the box, as the mathcad sheet does.

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Old 15th March 2003, 06:39 PM   #10
BrianGT is offline BrianGT  United States
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Here are the driver parameters that I am using for the Cabasse 21M18LB3/8 driver:

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