Tuning question

[97CamaroSPL]

I am in the process of builing a box for 2 audiobahn aw1200q's. It is 4.5 cubic feet total(single chamber) tuned @38hz.
They suggest a 4"x7.25" port(for each). Mine is only one chamber so do I need 2 ports of that same size to tune to 38hz?? The way I designed the box it has two port openings, but I haven't cut the portholes just yet, and I need to make sure before I do that.

[nda0602v6]

If you built two separate enclosures, they would be 2.25 cubic feet.

Using a vent calculator program I have, 2.25 cubic feet tuned to 38hz (using one 4" diameter port) says to use "one" port at (4" x 7.5" long).

For 4.5 cubic feet tuned to 38hz (using two 4" diameter ports), the program says to use "two" ports at (4" x 7.5" long). Hope this helps

[96firebird311]

Originally posted by nda0602v6:
For 4.5 cubic feet tuned to 38hz (using two 4" diameter ports), the program says to use "two" ports at (4" x 7.5" long).

Don't forget to subtract vent area from the box volume. To maintain a 38Hz tune, you'd have to make both ports a little longer. (Roughly 1/2") Question for ya. How much power you gonna have behind these puppies? Assuming your powering them at their RMS figure, I'm showing vent mach to be pretty strong around tuned freq with these specs. To remedy that, you could use four 4" ports that are 20.5" in length. Or, an even better design, you could use a single slot port. 12"x4" and 16.5" in length. [img]smile.gif[/img]

[97CamaroSPL]

Thanks guys, I'm getting really close to being done, I installed the (2) 4"x7.5" ports and cut the speaker holes today. All I need to do now is install speaker terminals, and carpet it. I'll get some pics up when I get done.

[97CamaroSPL]

Originally posted by 96firebird311:
</font><blockquote>quote:</font><hr />Originally posted by nda0602v6:
For 4.5 cubic feet tuned to 38hz (using two 4" diameter ports), the program says to use "two" ports at (4" x 7.5" long).

Don't forget to subtract vent area from the box volume. To maintain a 38Hz tune, you'd have to make both ports a little longer. (Roughly 1/2") Question for ya. How much power you gonna have behind these puppies? Assuming your powering them at their RMS figure, I'm showing vent mach to be pretty strong around tuned freq with these specs. To remedy that, you could use four 4" ports that are 20.5" in length. Or, an even better design, you could use a single slot port. 12"x4" and 16.5" in length. [img]smile.gif[/img] </font>[/QUOTE]Well its too late for that idea, but if I dont like the way it sounds how it is, I'll try it.
I'm running them with a hifonics bx1500d, so right around their rated rms.