Two Fi 18s + Two Fi 15s in same manifold

[blackhawk2383]

I have been reading about IB manifolds and I have a fairly simple question. If I was to build two seperate manifolds with two opposing 18" drivers along with two opposing 15" drivers as long as they were powered with two sepperate amps, would this be feasible? The reason I ask is that with a 16" spread in ceiling joists you could build a manifold that could house both two 15" drivers and two 18" drivers with one EP-2500 powering the 4 18s while another EP-2500 powers 4 15s.

I have a 5400 cu ft room that opens to a kitchen and hallway and I want to maximize my bass potential. The 4 Fi 18s split into two manifolds are a given but if I could incorporate 4 more 15s into the mix that would be nice as well.

[chrisbee]

Thomas, or others, may well have a more technical response but I have to ask whether you intend to turn down the 18s so the 15s can be heard? 4 x 18s will so outperform 4 x 15s on SPLs that the 15s will have to try very hard to keep up.

It might be fun to add the 15s in other parts of the room where they will be much nearer the seating position and have a better chance of matching output levels with the main 4 x 18 IB. Though you'd really need to confirm it would be beneficial using software like REW and a box sub to ensure you aren't making matters worse instead of better.

There is some interest in spreading the bass with extra IB subs but I haven't heard it tried it in practice. Except with a large front and smaller rear IB. There is no reason why an underfloor or ceiling IB couldn't be distributed around the room in separate manifolds provided the testing homework is done first.

[ThomasW]

Make life easy, build a manifold that spans an large enough area for as many 18"s as you want to install. It's ok if there's a joist in the outlet.