View Full Version : First time design check

09-08-2007, 12:16 AM
displacement is 0.19 for a 15" Fi Q.
net volume 3 ft^3
port volume 0.65 ft^3
port area 36 in^2
my calculations seem different from RE so can someone clear this up? my amp is mounted on the box as shown in pix, a good idea? i want to have some space in the trunk and as you can see the amp is really big. could someone explain port area in terms of SQ? i was thinking of a sealed box, so whats a good compromise between ported and sealed for a daily SQ? if anyone gets different calculations or tuning plz let me know, how you did it would be even better.

just used WinISD and got somewhat similar results. after displacement the tuning freq went to about 29hz. still dont know how RE volume calculations are different from mine.

09-09-2007, 12:26 PM
Any help would be appreciated. an answer to a question, a calculation check, or even “your design ***** and you should pay me $100 to design one for you” would be better than nothing.

09-09-2007, 01:34 PM
I am no expert when it comes to ported box, but here what i've learned from designing my 1st ported box. Don't trust the RE box calculator, it a good estimate, use winISD, it should be more accurate. In my case, using the same dimensions. RE calculated a lower tuned frequency as well as a bigger NET volume. Read the sticky "Simple EDU: How to design a ported box" in this section.

It pretty straight forward, basic you want 12-16in of port area for each cubic feet of NET volume (for you 36-48 in). If you are pushing alot of power, i would go for the higher number. The more port area, the lesser chance of getting port noise.

I don't have the Fi Q, but read alot on it b/c it was one of my top choice. Optimum tunning freq seem to be in the low 30's. Go here http://www.soundsolutionsaudio.com/forum/index.php?showforum=58

there are quite a few fi Q review, so read their setup and then determine what best for you. Somehow i feel your port area and displacement is a little small. I built as 2.25ft^3 box for a 12 in, and my port area was 39 in^2 with 1.04 ft^3 disp. and that at 33 Hz. So run winISD and double check.

09-09-2007, 03:24 PM
thanks for the input and the link.

09-11-2007, 02:57 PM
use the formula in my sig...you'll never go wrong.

09-11-2007, 04:48 PM
i just might but i dunno what those abbreviations are. ive already scrapped this box and am now designing by hand using winisd.

09-12-2007, 02:51 PM
i just might but i dunno what those abbreviations are. ive already scrapped this box and am now designing by hand using winisd.

Lv = Length of Vent
Fb = Tuning freq.
Vb = volume
R = Radius (of a round port...square root of Area/3.14 will the R value of a slot port)