Ok, i tried searching around and couldnt find a post like this that helped me too well.. let me start by giving you guys the info you may want to know. Im doing this system from the ground up. Got my 1/0 knukonceptz wire in, got the 220 amp alt about to arrive soon. Still kind of bothered by the amp i will be running, there is a SAZ1500D very close to me used for about $270 .. hard to beat that i guess :-/ And finally the sub.. For the past month ive been trying to figure this out i have pretty much figured on a 15" BTL. well like most of us i did a test run on fi's checkout system LOL.. did all but press the button and i realized there isnt a huge price difference in the 18" vs 15". This is going in a 1997 Chev. Tahoe so room isnt really an issue. Its obviously a bigger woofer but im just kind of confused now. Things running through my mind would be what if i ever take this system out? Dont know if the 18 will fit in much more than another SUV where the 15" i may have better chances...ive never heard a BTL in person.. i know im convinced just from forums like these and youtube im going to be very happy with my purchase.. has anyone used both the 15 and 18? is there a big difference between the 2? I think what im trying to do here is get your guy's opinions on my situation.. almost need someone to talk me into it LOL.. i dont want to piss away $500 on the wrong speaker.. appreciate any idea's you guys can fill my head with.

if u plan on having the tahoe for a while, i would go with the 18, u could always sell it later and buy a 15.

Well if you have the space for it go for the 18", it will be louder than the 15" in the right enclosure. Personally it is gonna come down to a compromise, either get the 18" and hope you have that vehicle for a long time or get the 15". Personally since I want an SUV so bad just to have an 18" in there I would or it would be 2-15"s so that is just me.

I have to agree with Brandon. While both will give you insane amounts of output, in a properly built enclosure the 18 will be louder than the 15 due to the extra cone area. Like he said, if down the road you get rid of that truck and get something smaller and have to go down to a 15, you won't have any problems selling the 18.

well... since you guys put it like that i would be a fool not to go with the 18" for like $30 more or something Thanks everyone

if room is no issue, i would go with the IA DP 21" then up grade to a second 1500 later. thats my opinion.

you always could recone the 18 down to a 15 if you ever change vehicles

if room is no issue, i would go with the IA DP 21" then up grade to a second 1500 later. thats my opinion.

He only wanted to know if he would need to take a 15 or 18 inch BTL, because their is only 30$ difference.

The IA DP 21" costs a lot more.

Cone area FTW!