Thanks guys...Matt is probably more inclined with function but I like my audio to look nice and discreet so I'm always trying different ideas that are based on theories.
Unless you give me an idea of what you want for an install I don't know where to start?
I've had one idea I've been wanting to try that is basically a keep it simple approach so that tuning is much simpler and less variables over all.
The idea is to use a full range driver matched with a mid-bass and sub woofer vs. the classic tweeter, mid, sub. This application will make it MUCH simpler for tuning and adjustment as well as install since the most crucial frequencies are grouped together within one driver. However, install is much more important with this too. I would place the full range driver either on the dash or hanging from the A-pillar. You essentially want to derive a radius using your crossover point on this full range driver. Once you plug in the Fs of the speaker and spit out a radius that is what you will use to construct your sphere to hold the actual speaker. The point of this is to reduce diffraction which will help get rid of a lot of issues with reflections as well.
Anyways, build all that...hang it from the a pillar or hide in the dash, somehow...your call. if you place it in the dash make sure it's as close as possible to the apex of the windshield and dash. It has to do with reflections again.
Once you're done there get a nice beefy midbass to reach about 60hz but preferably 40hz. I think matt found a nice mid-bass that's ~7inches. Again, INSTALL IS VERY IMPORTANT!!! 90% install and 10% hardware = sound. If you just hang speakers from a hangar don't expect much.
Now you can hide your sub in your vehicle ANYWHERE you want. Psychoacoustics play a big part in our ability to understand and process sounds. So essentially anything below 80hz is hard to localize by our ears unless it's causing vibrations. My sub can be seen in my profile pictures and nobody knows it's in my trunk. Most people think my mids are creating all the sub frequencies.
But anyways...that's a quick run through of an idea I'd like to try. Kind of burned out on swapping hardware so it probably won't ever happen. There's downsides to full range drivers that Matt will make sure you know aboutOne of them is lack of sensitivity. However, you make up for this through the fact that it's a near field environment and shouldn't be a terrible problem. I guess I'm done for now...i'll elaborate more if people have questions.
FYI...I'm not big on SPL or high output. My audio has hit 133db on music C-weighted. I'd only play it that loud for maybe 5 minutes. I like my hearing. The sad thing is that when your audio is tuned right you never wanna stop cranking and usually don't know how loud it is since it doesn't hurt your ears. Poorly tuned systems will hurt your ears at even 100 decibels.