View Full Version : Conflict with Box Calculations (sealed)

06-03-2008, 12:40 AM
I recently purchased 2 Alpine Type S 12" with the Dual 2 Ohm Voice Coils.
I started doing my calculations on how much air space I'm going to require.
I started by calculating how much air space I'm going to need based on the recommended Qtc of .86 from the manufacturer, and i get a volume of 2.04 ft/3.
But my trouble comes from the fact that the manufacturer lists 1.25 ft/3 as the optimum air space to get a Qtc of .86
I calculated this by hand and with an online calculator using my Theile/Small parameters for my driver. Is there something I'm Missing Here? I'm listing the Theile/Small parameters below if anybody wants to double check for me and let me know what I'm doing wrong

Fs 30Hz
Vas 61L
Qms 12.64
Qes .63
Qts .60
Xmax 12.9 mm
Power Handling RMS/Peak 300/900W

Any help would be greatly appreciated.

06-03-2008, 12:51 AM
My guess is Aline ran that sub's specs given the use of polyfil in a 1.25cuft box.

I ran the #'s in BBP6 w/ 'Typical' dampening and got 0.84 Qtc.
2cuft w/o fill or 1.25 w/ fill should give you similar results.