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Old 18th September 2008, 07:06 PM   #1
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Default BIB MOTH Build

Hello,

This is my first hifi DIY speaker build, and I was hoping someone more knowledgeable in this area could look over my cabinet calculations and provide feedback. I'd like to maximize the bass response as much as possible.

Would someone who has access to a speaker simulation program calculate the frequency response of these speakers with a BIB cabinet?

The MOTH BIB cabinet seems rather small as compared to the B20 dimensions. Size for me is not an issue.

Any recommendations are greatly appreciated!

Attached is the MOTH driver specifications, and below is the BIB cabinet dimensions.

Thank you!

-David


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File Type: pdf moth driver specs.pdf (53.4 KB, 65 views)
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Old 18th September 2008, 08:48 PM   #2
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Here's a picture of the driver.

-David
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File Type: jpg moth-driver.jpg (92.5 KB, 1705 views)
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Old 18th September 2008, 09:17 PM   #3
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It will be smaller -you've a much lower Vas. I make basically the same size, give or take a whisker.
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Old 18th September 2008, 09:24 PM   #4
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Greets!

Well, you inputted Vas/Qts as 0.21 ft^3/0.67 when it should have been 0.7416/0.67 respectively, so it's much larger at >9 ft^3.

Before going any farther though, you need to get them measured as the published specs aren't even in the same country as the measured specs I have, which will make it prohibitively large unless of course you don't mind anteing up for a couple of ~46 ft^3 cabs:

Re= 11.2 ohms
Le= 0.13mH
Fs= 47.3Hz
Qms= 9.6
Qes= 1.23
Qts= 1.09
Sd= 201 cm^2
Vas= 58.5 liters
Cms= 1.03 mm/N
Mms= 11 gramms
Rms= 0.34 kg/s
BxL= 5.42 N/A
SPL= 91dB

These specs in the 9+ ft^3 cab looks pretty bad, but you never can be sure till you build/audition one in-room, so as always YMMV:

GM
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Old 18th September 2008, 09:26 PM   #5
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Quote:
Originally posted by Scottmoose
It will be smaller -you've a much lower Vas. I make basically the same size, give or take a whisker.
Huh?! Am I missing something?

GM
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Old 18th September 2008, 10:04 PM   #6
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the specs say 21 'litters' .... not cu. ft.
therein the confusion I think
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Old 18th September 2008, 10:29 PM   #7
GM is offline GM  United States
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How so? He inputted 0.21, not 21..........

GM
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Old 18th September 2008, 11:08 PM   #8
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21 litres ~ 0.74 ft^3 not 0.21
Scott accepted the specs he had inputed.
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Old 19th September 2008, 02:26 AM   #9
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Default Updated Cabinet Calculations

GM & Hitsware, and all,

Thank you a TON for your help and thoughtful oversight.

Below are the revised cabinet calculations using GM's measured values. I had read in other professional reviews of these drivers that the measurements were different than the published specs, but could not find any other values. This was helpful.

Do these numbers look better?

-David

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Old 19th September 2008, 03:56 AM   #10
GM is offline GM  United States
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You're welcome!

Unfortunately, you didn't. The 21 L Vas is the published spec that you converted incorrectly/whatever. The measured Vas spec I posted is 58.5 L, so convert this to ft^3 using the spreadsheet's built in converter. If you don't wind up with the 46+ ft^3 Vb with the new Vas I mentioned earlier, then try again.

GM
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