So on my '04 D2 I have an aftermarket Kenwood head unit (came with it when I bought it), nice deck with Bluethooth, etc.
I recently realized my rear subs weren't putting out sound, the rest of the system cranks up pretty nice and loud hence why I haven't really noticed it.
I can hear very, very faint music coming from the rear factory subs which are in good condition and wiring all looks original.

My theory is that maybe there's no power going to the factory amp under the drivers seat. I've searched and searched but my head is spinning with all the stereo threads and RAVE confuses me even more (I can turn a wrench but not the best at reading electrical diagrams).

Would the other speakers work at all if the amp wasn't working or not powered? Is there a "power" wire in the factory head unit harness that supplies signal power to the factory amp to turn it on?
I've checked fuses, all are good under the steering wheel.

Thanks all. I have the Harmon Kardon factory system.

 

Got same setup but the subs hardly output overall music. I guess its mostly for the deeper bass.

 

I've been out for the past couple hours with my volt meter. There is a whole plastic harness (which is actually two that clip together, they are green and blue) that aren't connected to the adapter for the other factory harness connectors. I believe these are for the factory CD changer, steering wheel controls and factory amp power.
I've discovered that the peach wire on the green harness is power for the factory CD player, when I apply 12v to that, I hear the changer power up and I can eject the 6-pack changer cartridge.
I was hoping the red wire on the blue connector would power up the factory amp and get my back door subs going but no love when applying 12v. The black wire in the green harness is definately ground and tests for continuity when connected to chassis ground, not sure why they even had that in the harness, maybe for extra ground load.

EDIT: added photo with illustrations.

I'm still poking around but if anyone has any other input (audio pun intended) please chime in.

Thanks all.

 

Hiya, sorry to bring up an old thread but seems not one else ever found an answer.
Did you ever get these working? I have the same in mine with a factory head unit. changed the amp still no difference. been like it in the last 3 discovery's I have had. The old amps in the disco 1 were great

 

Same here...
'04 D2 with HK, the subs in the tailgate barely move.
For some unknown reason, the rear subs are Phillips.
Tried some aftermarket Pyramid 300W/4Ohm speakers - they move less than the Phillips.
Tried another known good amp, same issue.
I'm now trying to track down a true HK subwoofer assembly to see if they'll work any better - P/N XQA000010 (or AMR5511???)

 

I wouldn't waste your money
I tried dong that on my last discovery and it didn't make any difference. maybe the are just for show!
The disco 1 subs had a separate amp on the back you could hear them before seeing the car.
going to try one more amp and head unit and see if it makes any difference.

 

huh.

maybe a small cheap amp wired in right before the D2 subs would help out.

there's plenty of room in the door for a small amp.

 

Thanks!
I know next to nothing about car audio...
How about a separate sub woofer amp between the existing HK amp and the new 300W/4Ohm subs? Doable?

 

I have a separate JLAudio 300w amp where the CD changer was that feeds the two front door speakers and a JL 12" sub in the back... The stock amp feeds the rear doors and the tweeters. Works great.

I have to think there is some issue regarding the signal going to the sub that isn't right.. Though I'm no expert, my S model did not come with factory subs.

Are you saying you have low levels with a total stock setup?

 

Yes and no.

Hi end head unit w (worthless) factory nav, HK amp under driver seat. HK speakers in doors and “Harmon Kardon” on door tweeters, A pillar tweeters - but Phillips speakers in the sub woofer assy.

I have 2 sub woofer assemblies.
One OEM “Phillips” - speakers barely move.
One with Pyramid 300W/4Ohm subs - moves less than above.

My hope is that an HK sub woofer assembly will work.