im not master builder but from what ive heard the most is 4-4.5 cubes is premo for the 15" L7 and i got some, i got em in a a 3 cubic ft box, it feels a lil small, so im going for the 4.5 cubes, but thats just what ive heard, im just getting into this stuff, good luck with ur gear
i used that same site to do mine when i had a 15" L5. i had it in 5 cu ft tuned to 32 hz. all i did was change the port a little with it so it wasn't so skinny. i think it sounds great! i pushed it with a zx750.1 and i hit a 140.8 in my integra. i worked great for me for the most part. i wish i had gotten a higher number with it but i should have tuned it higher for that.
well this setup will be going in my friends jeep cherokee...he wanted me to hook him up with a system that would be pretty loud, but he wanted a 15" L7 for some reason....so i told him i'd build the box for him...and i'm hoping that it will perform pretty well in 3.8cuft at 33....btw i think he changed his mind about the amp he wants to run, but what amp would push the l7 pretty well but cost no more than 230$