Need Help w/ Sub Enclosure

[DaRealAce]

I need help designing a vented box for my new SI 15. I tried using winisd and got the vent tap and can't figure out the port's displacement. So any help would be great, hell if someone did the design from me that would save me so much time.

Heres the specs:
Re: 3.5 Ohms
Fs: 22 Hz
Qms: 3.7
Qes: 0.39
Qts: 0.359
Cms: 197.84
Mms: 262.73
Vas: 184.32 liters
Sd: 810 cm^2
SPL: 88.86 dB (1W/1M)
BL: 18.1 TM
Xmax: 26mm

Vented = 3.5 cubic feet tuned to 27 Hz.

Thanks!

[Romberry]

Originally posted by DaRealAce
I need help designing a vented box for my new SI 15. I tried using winisd and got the vent tap and can't figure out the port's displacement.

(snip T/S parameters and box tuning)

I'm not really sure what it is that you are asking here but let's hit it from the top. First, your T/S parameters don't macth up. A driver with a Qms of 3.7 and a Qes of .39 has a Qts of .353, not .359. The difference is ceratainly small but still...or were you figuring on approx 0.1 ohms series resistance (likely too low) for amplifier output impedance and speaker cable/crossover Z?

No matter. A 3,5 ft3 box is a wee bit (not enough to matter) undersize for even a QB3 alignment and your tuning is going to give you a small (less than a db) bump in the response for an octave or two above resonance.

As far as "port displacement", if I understand what you are asking (and I am not sure than I do) it should be a simple matter to calculate the volume (PiR2xL for round ports, HWxL for square rectangular ports) to make an allowance for port displacement in your box volume. A liter or two one way or another in a (large) 3.5 ft3 box is not going to make any gross or critical difference.