Slot Port Length by hand

[nickeveready 0]

i need someone to break this down retarded style because i want to be able to figure this out by hand as opposed to using online calculators. here are the specs...

external box dims h=18 d=16.5 w=40

-box 5.51 cf (net)

-desired tuning freq 32hz

-port surface area will be 82.5

-port height 16.5

-port widht 5

i know all of you experts will be able to help me out..thanks

[frankyp00 0]

I'm guessing 29.5 in. But I'm curious how others will break it down. I used JL audio's equation to do this.

http://mobile.jlaudio.com/support_pages.php?page_id=165

[nickeveready 0]

I'm guessing 29.5 in. But I'm curious how others will break it down. I used JL audio's equation to do this.

http://mobile.jlaudio.com/support_pages.php?page_id=165

well i got 29.41 with the carstereo.com calc(includes end correction) so this will be close enough plus this will also confirm that the calc is close to accurate

[creyc 1]

thats a really big port for such a small box. With a 5" wide port I'm getting around 52" of port length, and less than 3 cu ft volume. Maybe use a narrower port, 4" port would take the length down to less than 35" which would give you something like 4 cubic feet.

[creyc 1]

To those getting around 29", are you subtracting the port volume from the internal box volume? You're no longer working with 5.51 cu ft after you put a slot port in there.

[nickeveready 0]

To those getting around 29", are you subtracting the port volume from the internal box volume? You're no longer working with 5.51 cu ft after you put a slot port in there.

would this work...5.51cf originally my port is 1.40cf 16.5x5x29.41/1728=1.40cf..would i just build the enclosure larger to compensate for the the port displacement which would be 6.91cf?

and i thought the rule of thumb was to use 12-16 sq inches per cf, so 16x5.51=88.16 sq inches...so 16.5x5=82.5...the bigger the port the less chance of port noise right? please correct me if im wrong ported boxes are new to me

Edited June 8, 2008 by nickeveready

[creyc 1]

Things kind of work in reverse when you're restricted to a set of dimensions and you're trying to maximize the box to use all the air space while still maintaining port frequency.

If you NEED 5.1 cubic feet of airspace for your sub, by the time you add port volume to the equation your box is now 6.8-6.9ish, correct.

Which sub are you planning to run?

[nickeveready 0]

Things kind of work in reverse when you're restricted to a set of dimensions and you're trying to maximize the box to use all the air space while still maintaining port frequency.

If you NEED 5.1 cubic feet of airspace for your sub, by the time you add port volume to the equation your box is now 6.8-6.9ish, correct.

Which sub are you planning to run?

well the specs i posted originally were not for a particular sub..but im wanting to get one fi q 15 d2. this will be in a 99 mustang with a rear seat delete. i believe the q only needs 4cf max...dimensions im workin with are 16=d 40=w 20=h