I have an odd application. It's a very small car with no room for a sub. The biggest box/sub combo anybody has made is a .6 cu. ft. that will take a 10". That gets somewhat acceptable bass response and is good enough for most people.
But here's the twist: lots of these cars have a 4-point harness bar which cuts through the space where the 10" would go. For all those folks, if you have the harness bar, you deal with the 2 6.5" drivers behind the seats and 2 5.25" drivers in the dash and forego any sub bass at all. But with the harness bar in place, there is room for an array of 6.5" drivers below it. I could fit up to 5 total (including the 2 spaces on the ends where the stock drivers go). I modeled it with 4 Peerless SLS in a ported box and it looks like you could have decent sub bass and all the midbass you could ever want. See the attached graph. The green line is a JL 10TW3 in the .6 cu. ft. box on 650W. The blue line is 4 SLS taking up the same volume (including ports) on 450W.
As a side note, the other difficulty with the car is that the stock elecrtical system isn't the greatest, so feeding 650W to a sub and another 200W to the 6.5" is asking a lot. If I can replace it with 450W feeding the 4 SLS 6.5", that's a bonus.
So here's the question. Assuming I highpass the dash drivers at 160Hz, what problems would I have if I just ran the 4 Peerless drivers to cover sub bass and midbass up to 160? Sound localization should still be ok (enough) at 160, so the loss of stereo info wouldn't be terrible, right? I'm playing with ideas to see what the best solution would be. Any suggestions are welcome.