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Old 12th January 2008, 01:31 AM   #1
mhtplsh is offline mhtplsh  India
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Default woofer tester & LMS difference

I hv tested woofer with LMS & woofer tester(OLD) with same jig & place. There is difference of 10% in vas. Woofer tester shows 10% less Vas than LMS.
Is this ok?
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Old 12th January 2008, 05:45 AM   #2
simon5 is offline simon5  Canada
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yes this is ok, well below usual variance between tests
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Old 13th January 2008, 03:17 AM   #3
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The difference of 10% itself isn't much of an issue. What is important is making sure your test is repeatable no matter what system you are using. This means good clean impedance peaks with no bumps, blips, dips, etc. You should be able to put your woofer in the jig and run the same test over and over again without more than maybe 1% difference in any parameters. I did a post explaining some things about T/S measurement awhile ago that ou can find here.

http://www.aespeakers.com/phpbb2/viewtopic.php?t=927

John
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Old 13th January 2008, 03:24 PM   #4
Ron E is offline Ron E  United States
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I'd probably believe LMS before woofer tester.

I have heard talk about inaccurate measurements with older versions of the woofer tester, but I don't remember what parameter(s) were off. That said, I doubt its impedance measurements are off, I bet you could run impedance plots and calculate Vas yourself to be sure.

Vas (Really Cms) is sensitive to temperature, and also the suspension is nonlinear so measurement at different signal levels and /or temperatures can give you different values.
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