sub placement

So many factors to determine the best placement (ie. what is the box tuned at?, size of the driver?, desired SPL?, type of music?) sometimes people face subs towards the rear of the car to increase the soundwaves distance from the driver giving and impression that the sub is louder.  I think you are more open to cancellation when pointing your subs towards the rear of the car, build a small box with the driver that you are going to use and then put the box in different locations till you can find the location you like then go for the custom enclosure.

Why do you have to seal off the trunk like that if you don't have to do it with IB midranges and coaxials?

From most the info. i've read and situations I've seen you are actually going to experience less cancellation with the subs facing the rear of the vehicle.  But the advice to try different locations is a good way to go about it.

Also I thought sealing the trunk was a good idea for the IB application as well?  The idea being that subwoofers operate at high sound pressures and keeping the subwoofer's pressure wave isolated from it's back wave (like a sealed box) is going to be ideal.  That might be confusing but hopefully you get what I'm trying to say.

Not really.  The "sealing" of the trunk I don't think matters with IB speakers at all.  It doesn't really make sense to me.  I dunno I'll do some reading.

Exactly and the midranges and coaxials are not operating at such intense pressure levels so it doesn't make much of a difference.  I just figure in a IB the trunk becomes the enclosure, and thus leaks are bad. Especially leaks from the trunk into the cabin.