Specific Box Dimension Questions or The Math to figure it out

[CARgoB00M 0]

I am currently waiting on my q12 dual 2 to arrive, and it is going in my work van (E-150) Passenger Converted to cargo. I have a two fold question  I would like it if the box were no more then 15" front to back considering the sub facing front. 

 

My current setup has the sub firing into the back of the drivers seat as this is where it is the most protected and less likely to be damaged. I wouldn't mind using the ported box cutsheet for a Q12 as shown but I would have to put legs on the "face" and set it up so it was downfiring at the floor in order be able to carry the amount of tools/cabinets I typically do. (I am a cabinet maker so I can build anything you can imagine when it comes to a box) 

 

The box dimensions as suggested would be 17 5/16" front to back, I would still prefer the sub to fire forward so there is less chance of anything ever touching it what would I need to change the dimensions/port size/location to in order make the box no more then 14" front to back without changing the tuned frequency? I can handle doing an aero port or building a more complex design without issue so if anyone has a suggestions I would be extremely grateful. 

 

2008 E-150

Pioneer DEH-P3900MP Head Unit

JBL BP1200.1 Mono Amp (old but I love it)

Stock Power,  0ga wiring upgraded

 

 

 

This is basically my test bed for the car I am building and will determine If I go ahead with 2 q12's in my Camaro and go thru making a fiberglass enclosure for it.

 

 

 

 

[Quentin Jarrell 671]

All you need to do is make sure the surface area of the port remains the same square inches and keep the port the same length.

[NB50 206]

He needs to keep box volume the same also.

[CARgoB00M 0]

Ok so which dimension determines the port length, if you reference

 

 

Is the port length 16-9/16" + 3" + 17-7/16" = 37" length or 12-1/16" + 3/4 + 3/4 + 17-716" = 31" length? Which dimensions do I need to follow to determine the port length? 

 

Also could I just rotate the box 90º and have the port firing straight up or down with the sub facing front mounted on one of the 32-3/4" x 17-5/16" Sides without changing anything else? Or if I wanted the port on the same face as the sub my port opening would be 2.276 x 15.813=35.99" sq. but to do this I would need an answer to the port length question above, I am assuming it is based off of the 37". Also would the position of sub need to be moved?

 

Thanks for the help guys, I have built loads of boxes but have never gotten in depth into the math for frequency tuning and port dimensions and I really want this box to be as optimal as possible but still fit my needs.

Edited April 9, 2013 by CARgoB00M

[Quentin Jarrell 671]

Air is a fluid as long as you keep the volume the same, and the port area and length the same they all can be any shape you want.

You measure port length down the center of the port. So if the port is 2 inches wide you would pop a line at one inch and measure from there.

[BsEMS 1]

Your port length is 34

[CARgoB00M 0]

Box is built FedEx says my sub should be here Wednesday, I cant wait. Thanks for all the help and answers guys!