Port calculator w*h
 

When I switch width & height on:

http://www.carstereo.com/help/Articles.cfm?id=31

... it has a different port length. Is it because it calculates for the end of the port (in the box) to be either the W or H from the back wall? Is the lower vent length for the lower w*h number? Thanks.

bump......

Is this box 31.629 HZ or 29.7 HZ?

8.134 cf3

Port 7" x 18.5" x 30" length.

Two observations - first, don't use a 30" long vent. Second, it won't be tuned to exactly either of those so don't sweat it.

I dont get that.

It doesn't mean the port will literally be 30" long.

It means he needs 30" of length to achieve the desired tuning.

What if he only had 22" of depth, but needed 30" port length.....

All he would do is make an L-port to extend the length of port

Use this... 12 volt calculator.it's less deceiving.. you'll quickly see how far off your length is for them frequencies.

It shouldn't matter, if you switch up the width and height... :dunno:It's still the same amount of area, as long as the two ports remove the same amount of space the lengths for tuning would be the same. This might change slightly if say you use 3 or 4 boards to make a lower/center port vs one board for a slot port. The difference would be minimal but would remove enough air space to cause the port to be longer to accommodate the smaller internal space.

And of course going longer, means even more space removed... lol

Why not use 30" port length, does the air need to group? I imagine it'd be even worse as an L-shape.

I just lucked out if I invert the sub (no crazy decimals to measure):

internal space 8.09375
port area 129.5/7*18.5*29d
exactly 16 square inches per cube
33.5 HZ

38w x 20.5h x 29d (+1 baffle)

Pretty much what I want, between 30-34 HZ.

What's hard to understand? Do not use a vent that long. It is generally unadviseable to use a vent over 20" in length. If you vent calculates to that length then one of three things is wrong:

Your enclosure is too small
Your vent area is too large
Your tuning frequency is too low.

You can't just use a tuning calculator and jam any old vent into any old enclosure and expect it to work. That's how you get bad sound and/or poor performance.

Alright so what if a manufacture suggests an enclosure for a 10" sub to be 1 cubic foot tuned @ 30-33hz

I would LOVE for you to make an enclosure with proper port area, and still have a vent length under 20"

I didn't know that, I should have figured why companies recommend a port length with air-space.

What happends when there is more space from the back wall to the port than there is port width? Will it perform as if the port stops directly at where I've drawn it?

http://sphotos.ak.fbcdn.net/hphotos-..._7602015_n.jpg