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how to measure qtc after building enclosu

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=127163
Printed Date: May 12, 2025 at 3:07 PM


Topic: how to measure qtc after building enclosu

Posted By: teenkertoy
Subject: how to measure qtc after building enclosu
Date Posted: April 29, 2011 at 3:01 AM

There are countless calculators, spreadsheets and programs to model the response and qtc of a sealed enclosure. However, I cannot find any information about how to measure qtc of a speaker/enclosure system after it has been built.

For example, I know the transient response of a sealed system is directly influenced by the internal volume, but how can you measure when you get the volume just right, and achieve critical damping of qtc=0.5? (or any other goal you want for that matter)

I know resonant frequency can be found by plotting impedance vs frequency, and I imagine there is a similar electrical measurement to find qtc (or perhaps an acoustic measurement?)

-J

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Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."
Jayne: "We're gonna explode? I don't wanna explode.



Replies:

Posted By: DYohn
Date Posted: April 29, 2011 at 6:02 PM

If you have an RTA, you need to measure nearfield f3, then use your calculated Fc value and the Qts of the driver in this formula: Qtc = (Fc X Qts)/f3

Or use this calculator.

https://www.ajdesigner.com/phpsubwooferclosed/resonance_frequency_equation_qtc.php



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Posted By: teenkertoy
Date Posted: April 29, 2011 at 9:07 PM
Thanks DYohn, this is just what I was looking for.

-J

-------------
Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."
Jayne: "We're gonna explode? I don't wanna explode.





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