how to measure qtc after building enclosu

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?) -JMalcom: "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.

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.

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

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Thanks DYohn, this is just what I was looking for. -JMalcom: "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.