really building a box

Here is my delema I've brought 2 15" audiobahn ETERNAL subs I know the air total air space i need and thats about 4 cu. ft ok

one speaker needs 2  4" X 10" ports   port vel. 9%   -3db 27.36hz    tune freq. 35hz   sub disp 0.7 cu.ft    port disp. 0.125 cu.ft    total vol. 4.75 cu.ft   air space 4 cu.ft

the box i'm about to build is going to be H 16.5" X W 44" X D 23.5"  which is about 8.1 cu.ft

need to know how big of a vent i need for both speaker in the box               and per speaker if i go that route

need the vent side for the 2 speakers and                           just one

need the dim how deep high and wide for both and             for one

I would recommend that you make the enclosure separate for the individual subs. That way if one fails (heaven forbid) it will not affect the other and potentially damage it. So now to your question.

Vents: Each sub will get the best performance out of it (for most instances) with two - 4" diameter circle ports 10" long. I would look at heavy pvc piping from your local hardware store. If you are willing to splurg, look online for flared trims for the ports as well to minimize "flare noise". So a total of 4 ports will be needed. I also recommend that they be on the same baffle plane as the subs too if at all possible. This will resolve some minor "wow" issues that are common with side ported setups.

Best bet is to stick too the manufacturer's guidelines. I'm a little wary of this setup myself being that the VAS is 3ish cubic feet and the box they recommend is 4cf. But if that is what they say, then so be it.

My question to you is this though... What amp are you planning to pump this up with? With these two subs the only way you'll be able to reasonably hit 2600 watts or get somewhat even close would be to use Audiobahn's A2300HCT amp and wire your subs to 1ohm. MSRP early this year was $1,000, but it could have gone down by now... Just a matter of finding one, or at least fining an amp that can push the needed power and remain stable at 1ohm.

Well best of luck to you.

Ganbatte ne!