986 Bose rear deck enclosure questions

[politby]

Another question that has been only half-answered in earlier threads.

I am ripping out the Bose-MOST system in my 2003, replacing door and dash speakers, head unit and amp.

I also want to do something about the rear deck speaker enclosure, which appears to be not a subwoofer but rather some sort of rear fill kludge.

Anyway when looking at the pinout of the existing amp it looks like the rear deck enclosure is driven as 3 separate channels from the amp (rear L/R, sub) but other posts suggest it is really 2 channels with the "woofer" and midrange drivers in parallel for a 2 ohm load per channel. Does anyone know the real truth about this?

If there are only 2 channels of speaker wiring to the rear, my original plan of using head unit power for the rear midranges and bridged amp power for the subs (re wired in series for a 4 ohm load) is no good unless I pull new wires, which I'd like to avoid having to do.

The other option is to rebuild the rear enclosure, replacing the Bose drivers with a high quality 2-way system making 2 new channels, OR removing the midranges and replacing the woofers with a pair of high quality 6.5" drivers, effectively turning it into a subwoofer.

All of these options are really half measures, considering the unknown quantities of the Bose enclosure, but anything will be a great improvement compared to the awfulness of the existing system.

Any advice/opinions appreciated.

[Homeboy981]

I opted to replaced the deck speakers with 3-way 150w low-profile speakers and placed them on the topside of the storage compartment. They do not take up and storage space but when the top is down I have to open the storage box to hear them, the bass comes through great and it adds better "spatulization" (spreading the sound).

I ran those off my head unit (JVC-NT3HDTKW or something like that from ebay for $400). Or you could power them with another amp. They are plenty LOUD just off the head unit because they are ear level - so you don't want them to blow the other sounds out!

I also have made a wind deflector that is halfsize so you can hear the sound AND it still reduces wind noise. See my garage for all the details and photos. Pretty easy and cheap upgrades to make the car more updated.

TIP: Do NOT try to use factory wiring harness….that will save you a day on debugging the hiss from poor ground and insufficient wire gauge problems. GOOD LUCK!

[politby]

Okay, my little mod of the sub enclosure is done. I disconnected the tweeters/midranges and replaced the Bose woofers with a pair of Morel CAW538 8-ohm drivers wired in parallel for a 4 ohm load.

I did a little modelling in BassBox Pro and it looks like it may perform quite well as a lower midbass box but there are so many unknown quantities about the Bose box design that it might as well turn out the opposite.

But I had the Morels lying around anyway.

The Bose box turned out to be quite sturdy, nowhere near as flimsy as I had expected. Will put it back into the car tomorrow.

[politby]

Wow.

Managed to get an early Friday flight home and I have now spent a couple of hours in the car with a big grin on my face. This seems to be one of those rare occasions when a shot in the dark hits the bull's eye.

The plastic, doomed beforehand, Bo$e box has been transformed into a real sub! I wish I had an RTA so I could measure it, but what we have here is a dual 5" equipped enclosure that is both musical and plays LOW.

No rattles, no rumbling, just dry, tight bass that is more than enough for this little car. I put on Avishai Cohen's "Gently Disturbed" and expected one-note bass reproduction, but what came out had my jaw drop.

I think what happened was I had an enclosure that Bose actually spent some time carefully tuning and adapting to the Boxster cabin, then did their usual thing and put in some really crappy low impedance drivers and connected it to their severely underpowered amp.

Then I happened to have a pair of high quality drivers lying around which by another stroke of luck happened to fit physically and acoustically. Added some dampening to the box, real amp power and voilá...

Amazing. I could have spent a thousand euros on a custom job with no guarantee of a better result than this.

[SolidWorks Mike]

Originally Posted by politby

Wow.

Managed to get an early Friday flight home and I have now spent a couple of hours in the car with a big grin on my face. This seems to be one of those rare occasions when a shot in the dark hits the bull's eye.

The plastic, doomed beforehand, Bo$e box has been transformed into a real sub! I wish I had an RTA so I could measure it, but what we have here is a dual 5" equipped enclosure that is both musical and plays LOW.

No rattles, no rumbling, just dry, tight bass that is more than enough for this little car. I put on Avishai Cohen's "Gently Disturbed" and expected one-note bass reproduction, but what came out had my jaw drop.

I think what happened was I had an enclosure that Bose actually spent some time carefully tuning and adapting to the Boxster cabin, then did their usual thing and put in some really crappy low impedance drivers and connected it to their severely underpowered amp.

Then I happened to have a pair of high quality drivers lying around which by another stroke of luck happened to fit physically and acoustically. Added some dampening to the box, real amp power and voilá...

Amazing. I could have spent a thousand euros on a custom job with no guarantee of a better result than this.

If you have an iPhone, download the JL Audio app from the app store, it has a DB meter, and a RTA.

[politby]

Thanks for that pointer. Of course there would be apps for that...

[M1Ark]

Originally Posted by politby

Okay, my little mod of the sub enclosure is done. I disconnected the tweeters/midranges and replaced the Bose woofers with a pair of Morel CAW538 8-ohm drivers wired in parallel for a 4 ohm load.

I did a little modelling in BassBox Pro and it looks like it may perform quite well as a lower midbass box but there are so many unknown quantities about the Bose box design that it might as well turn out the opposite.

But I had the Morels lying around anyway.

The Bose box turned out to be quite sturdy, nowhere near as flimsy as I had expected. Will put it back into the car tomorrow.

What amp did you use to power these subs?

[politby]

Originally Posted by M1Ark

What amp did you use to power these subs?

This one

Using the 2 rear channels bridged.

Works great.