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View Full Version : Question about recommended port size



daver18qc
04-07-2009, 10:36 PM
I already built box for about 25 subwoofers, and i use WinISD Pro to make my boxes.

Now, the only thing i wanna know:

-Why do manufacturer makes box suggestions that include a port so small that the Air Velocity gets so high!?

I just checked for my alpine Type-R 12", they recommend 1.7ft^3 with a 3" port wich is 10 inches long...

When inputted to WinISD Pro, i get a crazy high air velocity, 285 feets/sec , doesnt that mean that you'd only hear air coming out of the port, or "Port Shuffle" ??

DNick454
04-08-2009, 02:25 AM
Yes, 3" by 10" is only 30 square inches of port area. If you use too little of a port area, you're going to get some horrible port turbulence noise.

daver18qc
04-08-2009, 02:33 AM
But, does it serve a purpose ? i dont understand why they suggest bad port choices for their products....

I mean, does it get louder with a smaller port even with all that port noise or what ?

SSS 18734
04-08-2009, 02:43 AM
I think he meant the port is a 3" aeroport, not a 3x10" slot port (which would actually be more than enough port area). It isn't necessarily a bad choice. They want their box design to appeal to the greatest amount of people possible. Reasons for making a small port are:

1) The box will be smaller, cheaper, and easier to construct
2) With that size port, noise won't be prevalent at moderate levels, even right next to the port. The velocity will only be that high at full RMS power and at box tuning.
3) The enclosure will be far away, often times in a trunk, which will suppress any noise at loud volumes.

I have a pair of 2000SPL's. They are very similar to Type R's. I built the box to Pioneer spec: 1.4 cu.ft. and one 4" aeroport per sub. I didn't have any port noise unless I was in the back seats at full volume. And even then, it was minimal. The ports weren't even flared.

But if you can fit more port area, go for it!