I'm looking for advice on a ported design for this driver. I've searched and other than mention that it likes 25 to 30 cf I have not found anything.
Room: Small poured concrete bunker (aka apartment). main room, 20x20x8
- flat down to 12 - 15 Hz at 115db
- No highpass filter required
Design style: sonotube (3rd story of a 3 floor walk-up, no 400 lb refrigerators allowed
I've been playing with WINISD and have looked at 3 sizes tuned to 12 or 15 Hz: 20cf 22cf and 25cf. Larger than that will not work.
Given the stupendous room gain I get in my 'bunker' flat to 12 Hz is probably a non issue even at 20cf and 15 Hz tune.
Port velocity and the first resonance is a concern.
First question. For a 10" port (lets assume flaired) what is the max velocity before turbulence occurs? I'm guessing max velocity will go up as port size increases. I've done some searching, but there does not seem to be any definitive answer on port size and velocity.
At 25cf and 12 Hz tuning a 10" port would be 28 meters/sec at max power, 20 m/sec at 600w. I'm guessing I'll never get near max power, but don't know. With a flared port, is 28 m/sec acceptable?
Anything smaller than 25cf it looks like I'm forced to go to a 15 Hz tuning to avoid port resonance and velocity issues.
Can I get away without a highpass filter with a 15Hz tune? That would make port length and the first resonance more manageable (between 170 and 220 Hz for the three volumes) What is the lowest acceptable 1st port resonance assuming an 80Hz crossover?
Driver and port clearance:
I understand I will need a minimum of 10" clearance for the port, what about the driver? With an 8' ceiling, I was guessing a max tube length of 6.5' to give proper port and driver clearance.
Anybody know the volume for this driver?