View Full Version : Porting/Venting? How do you know what size Vent is what Freq in What size Enc?

12-13-2003, 04:56 PM
Porting/Venting? How do you know what size Vent is what Freq in What size Enc?

Before anyone gets all Pissy and tells me their and OG Poster that invented car audio and are the one that makes this board what it is and I'm a noob ruining the board... :) just messing with you guys, please don't get mad.. I'm trying to make light....

I did do search and found a few posts on recomendations for Porting or Venting for certain woofers, but they really just gave me more questions...

This venting thing looks like an frickin ART/Science... :)

I know I have posted before that I'm looking at getting some RE XXXs.... I'm waiting on the Money, hopefully right after X-mas....

So Ihave been looking at RE's site at the stats or specs on the 12" XXXs..

It list several differet boxes... Thats great... Vented and sealed...

Then I read post after post from different poeple saying "" I put my in xxx cubic feet tuned at yyy HZ...

None of these are whats listed on RE's site... I'd think its their sub, they know best, but then also know a lot of you really know your ***** and have good reasons for building it the way you did...


1st. I don't really care for this question what size enclosure you have it in, but how did you figure out what size enclsoure to go with, since its different than REs site????

2nd. How does this work??? Is it a specific size vent in a specific size encloseure, that is tuned at a certain freq???


is it a Specific sub, in a specific size enclsure with a specific size vent is a certain freq??? and if you used a different sub in the same box it'd be a diffent freq?

Does that make sense???
I posted something simmilar before somewhere, but only got recomendations for sizes and I apprecieaded that, but I really want to know how we arrive at those recomendations...

I want to know why I'm doing it a certain way...

I messed around with a few box softwares and It didn't help much as I didn't know what I was doing...

12-14-2003, 12:21 PM
Yes. Porting boxes is an art/science....luckily I'm an artistic scientist :)

The size, length, surface area of a port are all dependant on the tuning frequency and size of the box. Nothing else matters here, however, each of these variables are totally dependant on the others.

Basically, if you change the height and width of the port, the length will change as well. More surface area generally means a longer port. There are tons of programs out there to help you figure this out without doing all the math, but I'd suggest you learn the formulas before you start messing with a calculator. Just like algebra in Jr. High....you gotta start with a pen and paper before you move up to a calculator :)

Smaller boxes need longer ports to achieve lower tuning frequencies as compared to larger boxes.

If you're trying to decide what frequency to tune your box, here's some help

26-33hz = SQ (sound quality. your box should pick up about every note and have a decently flat response when tuned in this area.)

34-42hz = SQL (sound quality with some balls. Will get louder and have a slightly peakier response than one tuned in the lower region, but will also fall off a little more above and below the tuning frequency.)

43-?? = SPL (Sound Pressure Level. Will get loud and sound like ****.....but boy, will it be loud)

12-14-2003, 08:28 PM
Thank you....

Boy have I got a lot to learn....