BMW convertible enclosure ideas

[Adrian_D 520]

It seems like I need to build a new box for the BMW cabrio install I fixed.

The car currently has a shitty ported box, which fires towards the back in a "tub" formed by a cosmetic fiberglass panel. Port fires to the front, into the ski port. Sub orientation has to stay as it is now, I don't want to build that cosmetic fiberglass panel.

The main goal is to have a loud'ish sounding setup when the hardtop is off, trunk open and closed and something that can put up a half-decent score with the hardtop on.

My first idea was to seal up the sub against the cosmetic FG panel as good as I can, use that as the sealed chamber of a bandpass box and have the ported chamber fire through the ski-port with the biggest port I can fit and the biggest volume I can fit. Chose a higher pass-band (40-80Hz for instance) and be done.

One possible problem I see is that when the trunk is open, bye-bye mechanical power handling. So the port will either have to be extended, or plugged. Completely blocked port wouldn't be too good of an idea for demos with the trunk open.

The second idea is to keep the current alignment, increase the box volume as much as I can and make the most out of it with a ported box.

Wouldn't that act as a bandpass box when the trunk is closed because of the fiberglass panel ? And it would throw my ported design out the window.

Here is what I have to work with:

Not the best picture of the setup put together

Current box:

Space I have to work with:

Biggest question is: simulate bandpass with trunk closed or build biggest ported box I can fit ?

[Tirefryr 1,742]

Verts suck. The only way I see you improving is to rid the back seats and build big in that area and use the trunk for amplifiers only.

[Julian 641]

I would do either a single 12 or dual 10 bandpass through the skihole, but You may not have enough space for that.

[Adrian_D 520]

Verts suck. The only way I see you improving is to rid the back seats and build big in that area and use the trunk for amplifiers only.

I've discussed that with the owner but it's a no-go

I forgot to mention that the box will house 2 10's.

[Julian 641]

Verts suck. The only way I see you improving is to rid the back seats and build big in that area and use the trunk for amplifiers only.

I've discussed that with the owner but it's a no-go

I forgot to mention that the box will house 2 10's.

How much space can you take up? I think the bandpass will yield the best results honestly, only bad thing is the space but if you play around with it you could probably get the box size down.

[Adrian_D 520]

I haven't worked out the math yet...

[Duran 387]

Is a 4th order bandpass possible?

[Sencheezy 689]

I think its neat to see whats under all those beauty panels

[///M5 2,833]

This is almost the only reason to build a 4th order BP. Hopefully he'll let you beef up the midbass situation to buy some depth in the passband.

[///M5 2,833]

He may not want to hear this, but building a box around drivers already owned in that car is not a good idea. Unless of course his are ideal for said box.

[Adrian_D 520]

Ideal my arse, they are some crappy Audiobahns. No swaying him around on the driver choice

Complete crap is under the beauty panels, sadly. The owner and I worked about an hour to shim the box around so the beauty panel fits over the subs. It's not my work, otherwise things would be different.

As for midbass, there are 4 6.5's in each of the back side panels and 4 on each door. One tweeter per 4 6.5's. He wanted way more tweeters but I talked him out of it (luckily). Midbass is actually "ok".

Basically I'm trying to band-aid it as much as possible without cosmetic or equipment changes. Math on space available coming up tomorrow.

Again, the 4th order will rely on having the trunk closed and sealing off the cosmetic panel as good as possible. So it's not going to be sealed ideally. The beauty panel is thick fiberglass.

[///M5 2,833]

I'd walk away. Might tell him something. Of if you won't walk, tell him you'll do it if something changes. Smells like fail.