Hi guys..
The components I use (6.5's) are currently crossed over at around 40 hz.. So all I'm really adding the sub is for the really low stuff.
I may up the crossover point to around 60 hz, then run the sub from 50 down.
Below 50hz the sub should (in theory) be invisible in terms of where it comes from.
Subs are only really placed in the boot because it's the only place they will actually fit, firing them backwards is the norm though. The only real disadvantage of having one up front is that they are considerably louder, so you have to make sure the sub is secured very well, otherwise they'll be lots of rattles to contend with..
Swiv
The picture I posted was only a provisional test which I did at a car audio show.. and one of the options I have considered is to add an MDF baffle to replace the alu cover.. The issue there is getting the cabinet sealed well enough, and the bottom of the compartment is also quite thin. I've already added several sheets of sound deadening, but it's still not strong enough to be a sub enclosure. So if I do go down the MDF top sheet route I'll still have to fibreglass/mdf the bottom of the enclosure.
If the bottom could be made strong enough then all you'd have to do is seal a few small holes here and there which should be quite simple..
In terms of the sub being able to fire through the carpet the plan is to cut the foam out over the sub, I'll then make the grill/spacer so the sub can move. I'll also cut through the standard mats and use some strong grill cloth or another permeable cloth to let the bass through.
This way it shouldn't sit too much higher than the standard mats. This sub has a 2 inch peak to peak excursion. A more normal sub should be much easier to fit and should be easy enough to hide completely..
My most likely course of action is still to make a fibreglass or partial fibreglass/MDf box.. I may even make a mould for it if anyone is interested..
If you guys ever have any technical questions you can always try
www.talkaudio.co.uk It's a UK based car audio forum. Erskine and I have been on it for years