Bose-Shmose. What is going on here?

[boris81]

I am looking to update the "subs" on an old German convertible roadster car, designed in the mid 90s. The car is awesome but the audio system is by Bose. I understand that there are many challenges in car audio, especially because of the space constrains but many of the design choices here have me baffled. I started by replacing the head-unit because I wanted the flexibility of MP3 and USB storage. Soon after I realized that I can do better without the stock amplifier. Now I'm looking into replacing the rear speakers.

The rear speakers are 6.5" woofers in a very strange enclosure, right behind the seats. I played with EQ and realized that there's almost nothing coming out of there below 100Hz. They sound like they are low-passed but I didn't see any crossover components so I assume that this is an effect of the enclosure. The enclosure is strange. I would classify it as a poor attempt at 4th order bandpass but I'm curious to see what you guys have to say about it.

The speaker faces the trunk internals where space is extremely tight < 1l. The back of the speaker is enclosed in a funnel type of thing < 1l with what looks as a port opening. So the question is what is going on here? Bandpass, mechanical lowpass, something else? Do you guys see any room for improvement?

 

[Wisounds]

Probably an infinite baffle alignment based on lack of space for an enclosure.

 

[boris81]

I saw a picture where a brave DIYer made an assembly to mount the woofer in a conventional way. The space back there is very tight, I estimate 1-2 litters although I can't tell if it's well sealed. In the stock Bose assembly the driver face is right against a metal wall, possibly the gas tank.

 

[ßart West-VL.]

boris81, the picture you posted is only visible to people who are registered at slkworld. Please upload it to diyaudio if you want it to be visible to all.

 

[boris81]

I'm sorry about the picture link.

Does anyone else care to share an opinion?
What was Bose looking to do and what would you suggest to improve it?

 

[ODougbo]

Doesn't look like they designed the car around the subwoofer, just found a place to stuff one in.

Is that an adapter plate out of aluminum? If so maybe you could fit one of these?

6W3v3-4 - Car Audio - Subwoofer Drivers - W3v3 - JL Audio

If you have time to let car undercoater dry, you could seal the enclosure - from the inside.

 

[boris81]

I'm considering a few cheaper options with excellent excursion capabilities and better efficiency.
Tang Band W6-1139SIF 6-1/2" Paper Cone Subwoofer Speaker 264-919 - Tang Band W6 1139SIF
Peerless 830946 6-1/2" Paper Cone Woofer Speaker 4 Ohm 264-1148 - Peerless 830946

I'm not confident enough with my carpenter skills to undertake such a construction and even then I doubt the enclosure will be larger than 2 liters. If I decide to make something my material of choice would be plywood or similar.

 

[ODougbo]

What's your box plan 😕

Did you check Sonic? Here's a page of them, they even a shallow mount.

6.5" Subwoofers | 6.5 Inch Car Subwoofers | 6-1/2" Subs

 

[ODougbo]

btw.......
How to Fiberglass a mold layup for car subwoofer speakers « Car Stereo & Audio

 

[GM]

Reminds me of what I had to do with an RX-7 roadster. Dual 6th order BPs mounted through the panel behind the seats, putting the cabs out in the open under the car with the rear chamber ports venting into the spare tire cubbyhole [that was anything but airtight] to get more gain BW, so ~aperiodically loaded 6th order DBR?

GM