I have a Pioneer set up with 4ch amp, 4inch splits with the little one on the dash at the front and 6inch sitting on spacers in the rear. The spacers just allow the magnets to sit down in that speaker cavity. I am really dissapointed with the base out of the system, say compared with very standard late model cars at work like Nissans and Mitsubishi and the wifes Pug. I went back to the place who just wanted to sell me a sub, but I don't want that much base (just a fuller sound), or it sitting in the boot and don't know how my gas tank affects it in between. He confirmed my suspicions that the issue is with only having a small box of air behind the rears and no real box at the front with them being in the dash. I don't know if he is right but what he said confirmed what I thought.
So I have delayed my solution, because it sounds ok but I have already removed the original first aid kit rear shelf because it looked a bit daggy and replaced with a piece of mdf and carpeted. I figure I can sit my vac tank in the rear side boot well and then cut a couple of 6 x 9 holes that go into the boot cavity. I think that is strictly illegal in our state to cut metal out of cars, but given the benz is rigid enough to have a plastic tray that is bigger than the speaker in the rear tray, I don't think it is a safety issue and I can't imagine the cops bothering a relatively old man like me about such things.
If I knew I could get a decent base sound out of a speaker that was many times the price but could operate with the small air space behind it, then I would go that way. The hifi guy reckons it wasn't possible and since I was showing him "an open chequebook" I figured he had no reason to mislead me.
But really interested if others have advice.
And I expect the front speakers would perform better if using the air cavity of the door, but I wouldn't dare chop up my lovely period door trims.
