Help with box design 2 15" L7

[dave7700]

I've got a Chevy avalanche and I want to put 2 15" L7 kickers where the midgate is at. I'm planning to do a kerfed port centered between the two subs. My question is how long would I need to make the port starting at the front baffle. They're a 3.75" radii on each and outer dimensions of box are 42w x 18h x 20 deep. Port width is 2.5 inches looking for 35 hz.none of the free calculators have any direction on kerfed port

2 15" L7

42 x 18 x 20

2.5" port width

16.5" port height

? Port length 35hz?

[Joe X]

So your port area is really low, 41 1/4" and it should be above 100 square inches, as for the kerf subtract half of the kerf radius from the effective length of the port to get the tuning, finally, give the most net volume to you can up to 6 cubic feet per driver on rated power.