Four 8" subs vs one 15"sub
 

I can get 4 8" high end subs(cdt 200 watts rms each) at the same price of 1 15" high end sub (alpine type r, 750 watts rms), both can handle 700-800 watts rms, and both work in a ported box of 2-3 cubes. Which one would you choose and why?

4 eights...... faster and better control....... generally speaking..... not specifically talking about those CDT's. Also looks WAAAY cooler!! What's the VC arrangement of those 8" ? Does the VC arrangement work with the amp you are thinking of using ?

I heard rule of thimb is that 2-8 = 10 inch sub, 3-8 = 12 inch sub and 4-8 = 15 inch sub. So ignoring all other factors, 4 eights might be similar to one 15. In your case, find out what load your amp can handle. It can be tough to get 4 subs to one amp depending on their resistance.

I have 2 8 inch subs that are 8ohm each so I can add two more and only show 2 ohm. If you have 4 8 inch subs at 4 ohm your amp needs to be able to do 1 ohm.

Other consideration of course is space. Might be easier to configure a 15 vs. 4 eights or vice-versa depending on where you put it.

Yeah, the subs are 4ohm svc, and the amp is 800 watts at 1 ohm. I've modeled both set ups on winisd, and the 4x8's come out on top in all parameters except sub 30hz output (partly due to their 40hz tuning), but from 30hz up they blow the 15 away...which makes me skeptical considering the xmax of the 8's is only 10mm vs. 20mm for the 15...and both have about the same cone area. I as well was thinking that the 8's may have better control, and offer possibly tighter, cleaner bass with more upper bass attack in the 50-80 hz range.

I think your decision will come down to what will fit better and how much output you want. I would say the 15 will be louder and play lower, but not necessarily faster.

I'd choose the 15 for simplicity and low end response.

How much of what you listen to is below 40 hz anyways??

15" is definitely easier, but never met a really good sounding 15". IF you want this setup to sound good, go with the 8" hands down. 8" have never failed to impress me. Mind you, I have 6 eight inch sitting in the garage and I'm building my car for a single 10" !! Reason for that is I don't have an amp to make the 8" work and I'm a cheap bastard !! Using what I have already. :P

A lot of the rap I listen to touches below 40hz for a short time. Most is 37-45hz, but low end is something you eventually want if you're going for SQ, it's like something's missing. Apparently the JBL GTI 15 sounds excellent.

If you want to use a 15", it's best to have a great midbass that plays waaay down................. but that's only my opinion.

^ That is definitely the biggest challenge of running a 15... having enough midbass to keep up.