Thanks for all the replys people really useful information has given me alot to think about.
[quote name='Phil Starr' post='1212215' date='Apr 26 2011, 11:58 PM']There is probably no technical problem in changing the drivers for bass ones other than just choosing the right ones. If you start with a ready built cab then the choice is going to be limited. Most bass cabs are ported cabs for the very good reason that this is the best way of getting a decent level of bass out of a relatively small cab. Tuning a ported cab is critical for a decent sound and you'll need to get to grips with all this to get a good result. If you tell me the size of the cab I can suggest some drivers that you might consider. The internal dimensions would be good.
You should realise however that there may be some woodwork involved in adapting the cab. Four 12" bass speakers are going to cost you £200-300 for anything reasonable and more if you go for lightweight or better quality. You'd probably get as good a result with less hassle by selling your cab and putting in that extra for a bass cab you can try before buying. Not all 4x12's or even 4x10's sound the same or give the fuzz you want.
On the other hand you may enjoy fiddling around with speakers and you'll learn loads in the process. If you can afford £200 and don't mind if it is only a partial success then you'll find loads of people here to give advice.
Over to you[/quote]
Hi thats encouraging to hear, im definitely up for having an experiment, I figure as long as any cutting can be on the baffle then it should be fine as this part of the cab is removable although a pain it is doable and therefore reversable. The external dimensions are 14.5"x28.5"x30.5" thats depth, height and width abviously need to lose an inch or so to take into account the thickness of ply used, and an extra inch from the depth due to the recess from the picture frame front. I realsie selling and buying a bass cab would be sensible but my Bass 200 is in Green tolex as is the 2x15 so I'd like them to match the 4x12 and as the Green is no longer available from Matamp getting them to build one for me isnt an option either.