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Qtc vs box size and sub volume rating

Old 02-20-2007, 12:07 PM
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Qtc vs box size and sub volume rating

I bought an Infinity Kappa 102.7 10 for my boat. I am slowly learning some of the variables of sub installs. (Amp is JL E6450, bridged 5&6 channles to 300 watts, 4 ohm)

Thiele parameters for Qtc calculations are:

Vas 1.62ft3, Fs 20.40, Qts 0.45

The manufacturer recommendation for sealed is 0.75 ft3 which yields a Qtc of 0.8 with an F3 of 32.5hz.

My understanding is for flat response ie all Sq you should be Qtc of 0.707.
But for most all around listening you should target 0.9 to 1.1 for a Qtc in a sealed application.

If I plug in the parameters to get Qtc at 0.9 I end up with a box volume of .54 ft3, F3 is 33.84 and if I go to a Qtc of 1.0 I get a volume of 0.411 ft3, F3 is 35.64. These volumes would be great if they work as I need a small volume box.

Question am I correct that I can go to 0.54 ft3 and get a good mix of Sq and Spl with the 0.9 Qtc? Peakdb, or ripple is 0.8db at 0.54ft3.

Or has Infinity made a typo on parameters or on volume recommendation?
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Old 02-20-2007, 12:39 PM
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chances are with a box that small you would have almost no low end bass.
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Old 02-20-2007, 01:35 PM
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A QTS of .707 is a middle ground between transient response and damping and also gives maximally flat response...

I would recommend going this route unless you have a reason not to and have considered all the trade offs....
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