About to build a box for 2 15"s FI BTL's that will be going into a 87 Mustang.

Each btl needs 3-5 ft^3 and is .21 displacement.

This is my first Wall / Semi wall build so i just wanted you guys to look over it and tell me what you think.

You might have some port noise, as it is just under to suggested ratio of 9:1 for port height/width. The tuning is pretty high approaching 38Hz and you'll need a good amount of bracing. After bracing you will be scraping the minimum recommended box volume of 3ft^3 per driver and will be into the tuning range of 38hz.

if you take that and make the port from 4 to 3.5 it would bring the tuning back down i had to do that to my box too when i used that to make my first box b/c it was tuned to high for my sub

Shit can the RE Box calculator! It does not account for sub or bracing displacement! Better off to do it with paper and pencil!

If i increase the width to 30 that will give me 32.12 hz

And 9.10 cu^3

Im not good with measuring port area and what it should be relevent to the size of the box for it to sound good tho.

If i increase the width to 30 that will give me 32.12 hz

And 9.10 cu^3

Im not good with measuring port area and what it should be relevent to the size of the box for it to sound good tho.

Measuring port area isn't shit. You probably just think its more complicated than it really is. When you look at the front of your box, the port is a 2 dimensional rectangle. Right? Well the area of this rectangle (base x height) is your port area for your box. When you talk about port area, you talk about it as a ratio between port area and the net volume of your box. Fi recommends 12-16 square inches of port area per cuft of net volume. Lets say the area of this is 100 square inches and the box is 6 cuft (net volume; meaning after sub and port displacement). You divide the total port area by the net volume of the box (100/6) and you get 16.7 square inches of port per cube of volume. This is a little above the range which isn't a problem except for a long port. Sometimes port area has to be decreased so the port length will be decreased so the box will fit into the space your have in your vehicle.

However, if you increase your port area, the port length needed will have to be increased to stay at the same tuning. So lets say i cut down the port area of the box from 100 to 80.. (the port will have to be shortened to keep the same tuning; so it will displace less volume so your subs will have more net volume now) lets say your net volume is now 6.5 cuft. Now 80/6.5 is 12.3 You're still in the range so its good.

It's really a number game.. sorry if this is hard to understand.. read it multiple times if necessary..