I've been wondering... What is the optimum or target, port air velocity number? Is there a optimum velocity of air for ports? Say 40ft per second vs 80?

How does this work?

Thanks in advance!

 

Paul, how are you measuring this?

 

Measure, no.... model, yes.... I'm just curious. Thumper mentioned it one day. I've always wondered since then. lol

 

Use your ears. 14-16 square inches of port per cubic foot should be your target velocity. Your target velocity is lots and lots unless your sub is over excurting, it does need some dampening.

 

what in the flying ****?

 

yeah bro, I'm lost too, and I'm who decided to talk about car audio in an interview to get a job with a financial company. how they connect I don't know, just like I have no clue what you're talking about. sounds like you're describing port area

 

Rule of thumb - for a quiet room the limit is about 5% Mach, for a car around 9% Mach, and for an aeroport around 13% Mach. Speed of sound is ~1132feet/second so that's 57fps, 101fps, and 147fps respectively.

The faster it goes, the more likely you are to hear it.



That square inch per cubic foot thing is junk.

 

You want to keep your mach rating under 0.16 or under 30m/s/hz at your peak frequency for your box, or you will get whistling. There is no optimum, but bigger is usually better for effeciency and not having whistling ports. Butwith a bigger port you also get a faster rolloffof output from your enclosure, and may create "chuffing", when this happens with a big port you should shrink down you internal volume but must correct port length. my box had a velocity of 13 m/s/@44hz and was 2.5 cubes with 101 sq.in tuned to 38 hz and after alot of tria and erroe was the perfect for me.

 

Dukk/Lowtones, Thanks for your input. I'll do some calculations.

 

Lowtonez brings up a good point - it IS possible to have too much port area as well.