I'm looking for help with a Pi alignment for following car subwoofer. (I use this alignment with an Altec 515-8g at home and love it but someone else made the calc for me.)
Driver: Image Dynamics IDQ10 D2 V.2 Dual voice coil. Will series wire for 3.7 ohms Re Fs 23 hz Qes .345 Qms 4.77 Qts .322 Vas 2.26 cu ft Sd 350 cm2 SPL 89.4
I would like to use a 2.5" dia port The manufacturer has some recommendations but have no idea what alignments.
Wayne Parham Messages: 18756 Registered: January 2001
Illuminati (33rd Degree)
The Image Dynamics IDQ10 woofer looks good in cabinets from 0.5ft3 to 1.5ft3 tuned to 26Hz. PiAlign suggests 0.75ft3 which provides a nice flat response curve that is slightly overdamped. It has f3 of 40Hz and f10 of 25Hz, so it will sound very nice in home or in a car. Being slightly overdamped, room/cabin gain will effectively conjugate its amplitude response. For subwoofer use, you can go a little larger, to 1.0ft3 or 1.25ft3. That will give f3 closer to 30Hz, but f10 is still around 25Hz. The larger 1.0ft3 cabinet makes a great alignment for use outdoors or in very large rooms, but may sound a little bit boomy in medium to small rooms or in your car.
One more question My enclosure looks like it will end up at 0.86 cu ft for the space I have, very close to the pi alignment volume. What frequency should I use for port tuning? I could reduce to .75 cu ft if it matters.
Wayne Parham Messages: 18756 Registered: January 2001
Illuminati (33rd Degree)
Tune the cabinet to 26Hz. The IDQ10 works well in cabinets from 0.5ft3 to 1.5ft3 tuned to 26Hz. If you made the cabinet larger than that, you might want to tune lower for an EBS alignment. But in the 0.5-1.5ft3 range, 26Hz is the best Helmholtz frequency for that woofer.
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My enclosure looks like it will end up at 0.86 cu ft for the space I have, very close to the pi alignment volume. What frequency should I use for port tuning? I could reduce to .75 cu ft if it matters. 
