Originally Posted by AndriusLT
Hello am trying to build a sub box for my BMW E39
For my 540, I had a shop fiberglass an enclosure into the side "scoop" at the very back of the trunk. They integrated the original release latch, so I could still access behind to get at the battery or fuses or whatever it was. That was pretty good, though not going to crack the windows due to small enclosure size. As I noted in the other post, I would NOT put woofers right up against the seat back.
With the sub box somewhere else, the ski pass through makes a kind of port compared to the trunk "enclosure" so in theory there could be a bandpass effect, but it didn't seem to be an issue at least with my layout.
One alternative could be to make a slot that would fit up to the ski-pass, with woofers mounted inside the slot
or like half of this thing if you have space; the push-pull reduces distortion
If you wanted to be really tricky, taper/angle slot so the woofers almost touch at the back side. That could reduce some slot resonances, and *theoretically* have better airflow. Then again, woofers directly facing each other cancel out some vibration.
I don't recall the ski-hole as being large enough to fit a slot for 12s AND fire ports through. And NO, don't fire them through the slot, the airflow won't work. Actually 2 12s sealed with good amplification will get a lot of SPL in the car-if it is not enough, build something huge and just drive around with the back seat folded down!