RS5 B&O rear speakers not working, possible solutions?

[UTRS5guy]

Hi guys, I picked up my 2013 RS5 this weekend and was playing with the stereo and thought it was weak. When I faded all the sound to the rear it sounds like the only speaker making any noise at all is the one behind the passenger seat on the side panel. Nothing in the very rear is working at all. Is there a specific fuze that runs these or an Amp that runs just those speakers? I would think that if the speakers were blown they would make some noise and just sound like garbage right?
I am going to try to get some time this week to look around at the fuzes and the wiring, just hoping someone had some experience on where to start troubleshooting.

Thanks IA

[hahnmgh63]

Not much help but if you have Vagcom you can scan the Radio module and see if there are any faults. The B&O amplifiers are known to fail fairly often, enough that I bought a good used one off Ebay and saving it for either my RS5 or the wife's Q5 assuming one will fail eventually.

[Smac770]

An interesting point I noticed in the A5 SSP regarding the B&O J525:

Service
For the first time in an Audi, the various sound curves (equalizer settings) for the various specifications (right/left-hand drive, leather/fabric, petrol/diesel engine) are no longer stored completely in the amplifier. If the amplifier is coded in the workshop using the diagnostic tester, the diagnostic tester downloads the relevant sound curve onto the amplifier from a central data server. This has the advantage that the latest sound curve for the vehicle can always be installed on the amplifier.

There's five amp channels that go to the rear in the A5 B&O setup: one to a tweeter and woofer in each side panel, one to a mid on each end of the rear shelf, and one to the sub in the middle of the rear shelf. That's a lot of speakers to be not working. You might want to look at the amp behind the left cover in the trunk; see if it appears to have had any water exposure. Beyond that, as noted, you'd want to scan for DTCs. And maybe pull the speakers and separately test them.

[hahnmgh63]

Smac, the B&O amplifier is my '13 RS5 is the same part# as that in my wifes '16 Q5. Are you saying you think the hardware may be the same but the two amplifiers may have internal factory loaded software that is vehicle specific? If so, I better look back and check which Audi (A5,S5, A4, S4, RS4, Q5, etc...) my amp came out of.

[Smac770]

Yeah, that's my impression from that statement. The DSP parameters such as delay time and equalization curves and such would be different for the different body layouts. The SSP implies that's part of the adaptation process (such as "replace function" in guided fault finding). A dealership tech wouldn't know about this per se because they just push the button that the documentation says to push. But it very well could be the replace operation (which would address component protection) also knows for this unit to lookup and load the appropriate customization parameters for the chassis. Or it might be a separate operation.

The concept certainly makes sense. I just don't know how one would go about validating it without a scope and RTA and careful measurements of the amp channel output signals between an amp known to have been factory installed in two different B8 bodies. It could have been "a nice idea" that they dropped, or it is a real thing.

[hahnmgh63]

Well, it looks like the spare I purchased came out of a S5 so it should be a perfect swap to my RS5. I think my wifes Q5 is having an issue that's why I purchased the spare to try. The sound out of the lower front door speakers is very garbled. No faults, Audi says it is normal as these are just for Bass. The lower speaker in my RS5 are the same part # but the sound and/or words are quite legible. For one, I think if an Audi mechanic doesn't see a code/fault, he just assumes all is good. Wasn't even will to check the used cars on their lot to make a comparison which is what I asked them to do.

[Smac770]

The sound system is designed generally the same across all the B8 products. The B8.5 front door B&O midbass driver should not be the same though. A4/A5 should have 8T0 035 415 B and Q5 should have 8R0 035 415 C. but functionally, they should be the same.

I need to make new captures now that I have a correctly generated pink noise file. But the old caps I have, iirc, are showing the front midbass playing flat from around 55Hz up to around 700Hz. There's a lot of music in that range.

If the issue seems specific to one door vs the other, I'd swap the pins on the J525 plug and see if the issue stays with the original door or changes to the other door. If the issue is with both doors, then I'd hook up a different speaker and see if it sounds cleaner just holding it vs the original.

[UTRS5guy]

Found the culprit... Always helps if the actual speakers are present. The Amp is still there, assuming it's the one on the driver's side compartment in the trunk. Now I gotta figure out if normal speakers work with that B&O amp. I have other amps available if not and I'm sure I can sell the amp to someone who can use it.

[Smac770]

The B&O speakers tend to be normal 4Ω or 6Ω loads, I forget which I measured for all of them. So some normal speakers should be fine, if you mean some aftermarket 4Ω or 6Ω speakers by "normal".

[UTRS5guy]

The B&O speakers tend to be normal 4Ω or 6Ω loads, I forget which I measured for all of them. So some normal speakers should be fine, if you mean some aftermarket 4Ω or 6Ω speakers by "normal".

Yeah that's what I meant. I know in the past I've had some issues with Bose systems. I think the speakers wouldn't work with an aftermarket head unit or something wonky, it was years ago.