1. ## Wana check my numbers

I want to build a center slot box for two 12's using .75 material, the subs qts is .106. I want the box to be 36x13x22 tuned @ 32. How wide will the port need to be?

Using RE's calculator (I heard doesn't account for port displacement) it says if my port is 3.75" I'll be @ 31.08 with a box vol of 4.104. If I change 36 to 35 (for estimated sub displacement) it accounts for .137 and changes the tuning to 31.61.

I don't know how much volume the port will take up. Would it be tuned close to 32 after port displacement, or is that already accounted for?
Last edited by moparerrnocar; 12-31-2012 at 10:34 PM.

2. ## Re: Wana check my numbers

3.75+ 1.5= 5.25-width, height=11.5?, length of port = ?
multiply those three and divide by 1728

3. ## Re: Wana check my numbers

Originally Posted by SMS
3.75+ 1.5= 5.25-width, height=11.5?, length of port = ?
multiply those three and divide by 1728
Im a bit confused with the formula you posted....

I think I figured out my port volume. I took 17.5x1.5x11.5 = 301.875 converted it to ft3 and got .175. Port and subs equal .281

Changing the box width from 36 to 34 is a .273 difference which puts me at 32.171 Hz according to RE. That is if they don't account for port displacement.

Edit: I get what you mean now. I have to factor the port area as well as material volume. If so, then my port displacement is .611

So then .611+.106 = .717 of total displacement? If I change the width to 31 that's a difference of .682 and puts me @ 34hz.

Does this sound right?

4. ## Re: Wana check my numbers

Ok Im just confusing myself, but hear me out. I figured out the volume of my box 11.5 x 34.5 x 20.5 = 8133.375 / 1728 = 4.7068.

4.7068 - .611 = 4.0958

RE says 4.082??? Close, so they obviously factor port area. Now I just need to know if a 3.750-3.875 port puts me within 32hz.