No sound from rear speakers

[Kobajs]

Hello. I've had my Audi A4 for almost 2 years now. And up until recently I've always thought that I didn't have any rear mid speakers what so ever. But when I did a random scan on the car using OBD 11 the other day, just to see if anything was up with the car I noticed that I had 2 fault codes for open circuits to both of my rear mids. So I immediately removed the door panel for my passenger side rear door and to my surprise I actually had mids in the rear.

To the actual fault now, they don't produce any sound. What so ever (the tweeters work). And since I couldn't find anything useful on the googles I did some trouble shooting myself. And before you write anything about an AMP. I don't have one. I have checked every location where people have said on other forums and threads that there might be one, but to no avail.

I used a multimeter to test the cable, and there was a connection between the plug on the back of the stereo and the speaker wires. This makes me even more positive on the fact that there is no AMP in my car, since to my knowledge the multimeter wouldn't be able to get a connection if there was an AMP in the circuit.

The other weird thing that might have something to do with it is that I can't fade my sound front to back, but I can balance it from side to side. Also, the tweeters work perfectly, which also seem to be connected to the same wire as the mids, but are then split or something in the door. (The mids and tweeters have power from the stereo when using a multimeter to test for a broken cable).

I have the AUDI Symphony system, without a rear sub.

Please help me, I am literally going insane over this. This just doesn't make any sense in my head.

[Chrisc84]

What year is your car? Have you checked your fuses yet?

Sent from my SM-G973U using Audizine mobile app

[Kobajs]

My car is a late 2008 AUDI A4 B8 3.2L Quattro. Yep, the fuses are all good.

[Smac770]

The sound systems are pretty well documented by Audi, if you know where to look.

You have the CAN bus infotainment system with the Symphony head unit, ok. But that doesn't say anything about the sound system side of things (amplification and speakers). There are four sound systems in the B8 A4. Basic (8RE), Basic Plus (8RX), Standard (9VD), and B&O (9VK). You said you do not have a sub (rear deck for sedan, under spare tire for wagon), so you do not have the Standard or B&O sound systems. As such, it's expected that your speakers are attached to your Symphony head unit, since the Basic and Basic Plus do not use an external J525 with the CAN system.

I assume you're saying that the tweeters high in the rear doors are working? But the main speakers low in the rear doors are not working? They are in parallel connected to the same two wires at the door harness plug (pins 20 and 22). What exactly is the complete DTCs you are getting? Have you tried powering the rear main speakers with another amp solution to validate if the speakers even work?

When you say you can't fade front/rear, you don't have the control in the UI? You have the control but it's grayed out or such? Or you can interact with it but it seems to accomplish nothing?

[Iceman502]

Based on my experience the speakers are probably blown. At 94k, I've gone through 4 of them, all mid-range speakers in the front or rear doors. Smac is definitely far better versed in this arena so I agree, post the DTC's. Mine were all open circuit faults.

I called these guys and it was $80 shipped for a replacement pair https://lifetimeaudiparts.com/

[Kobajs]

Basic sounds about right by your description yea.

Yes, the tweeters work. But the speakers lower down don't.
No I have not, that was the next step I was going to take. Just don't know how to do that yet, since I don't have an AMP lying around.
What I mean by not being able to fade front to back is that the option is there. But there's no difference if I have the sound faded all the way back or all the way forward in the UI.

The DTCs I'm getting are
00872 and 00873.

[Kobajs]

But wouldn't the speakers still produce sound if they we're blown?

The DTCs I'm getting are
00872 and 00873.

[razir66]

Not if the voice coils are blown, it's an open circuit.

But wouldn't the speakers still produce sound if they we're blown?

[Smac770]

The front and rear lower speakers are different part numbers in the 8RX basic plus sound system. But they might have the same plug, which would be sufficient for you to swap them just to see who makes sound.

I don't know about frying to the point of an open circuit; I would think more likely that the coil is fried and seized in place. But if you have physical access to the woofer, you can see if it moves freely or is frozen. Hell, they could simply be unplugged.

But as for the DTC, there's usually more to it than just a number, such as the subcode and the text it actually represents, such as:
5 Faults Found:
00870 - Bass Speaker Front Left (R21)
011 - Open Circuit
00871 - Bass Speaker Front Right (R23)
011 - Open Circuit
00872 - Bass Speaker Rear Left (R15)
011 - Open Circuit
00873 - Bass Speaker Rear Right (R17)
011 - Open Circuit

So you have 00872 and 00873, which identifies a problem object, but what's the subcode that says what the actual problem is?

[Kobajs]

Wow, did not even think about just trying the front connector. 20 IQ from my side there haha.

Since I'm using OBD 11 and not VAG COM my stuff looks a little different. But I took screenshots of both codes so you can see.
https://imgur.com/a/i1JM6qU
https://imgur.com/a/tsHUYcB
Sorry I didn't manage to make the pictures appear here so I just put the links to them there.

All it says is
Fault code: 00872
Status: Static
Priority: 5
Frequency counter: 1
Driving cycle: 54
Mileage: 250083 km

And the same values for fault code 00873

[Smac770]

It gives the code text and subcode text in the screen caps, so "open circuit". Curious.

[Kobajs]

No idea what it might be? Besides maybe blown speakers?


Sent from my iPhone using Audizine

[Smac770]

Well, the interesting part is there are two speakers on that amp channel. Yet the DTC mentions the bass speaker. The assumption is that somehow the amp is equipped with diagnostics to realize the current flow at the different frequencies. And it seems to feel there's not the current flow in the bass frequencies that it expects to see. So it assumes there's an open circuit. Since the tweeter is actually playing and just the woofer is not (in line with the DTC statement), then the issue is at the point where the wiring splits, in the door, down to and including the bass speaker. So either the speaker is broken, or the wiring to it is broken (in the door though, we know the wiring to the door is fine, the tweeter works), or it's just unplugged. It's a slim chance that the problem is the amp, which in your case would be the head unit. Logical step one, swap the woofers front/rear (you don't even need to mount them, just plug them in) and see what works where.

[Kobajs]

I've tested the wires from the connector at the back of the head unit all the way to the actual speakers, both the tweeters and the bass. So that is out of the question, I will try to test the speakers in the front doors tomorrow. I'll let you know!

[Kobajs]

Yep, the rear speakers are definitely blown. Tried to plug them in to the front connector and they we're completely dead. I wasn't even able to move the voice coils by pushing on them. I'll have to buy new ones, probably going to upgrade the whole sound system while I'm at it. Thank you for all your help! Much appreciated!

[jelan]

Yep, the rear speakers are definitely blown. Tried to plug them in to the front connector and they we're completely dead. I wasn't even able to move the voice coils by pushing on them. I'll have to buy new ones, probably going to upgrade the whole sound system while I'm at it. Thank you for all your help! Much appreciated!

I have the same issue. Did you replace the speakers? Did it fix the problem? Where did you buy the replacement speakers?

Thanks

[Kobajs]

I have the same issue. Did you replace the speakers? Did it fix the problem? Where did you buy the replacement speakers?

Thanks

Have not been able to yet, so I can't tell you for sure. But I'm positive that this is the problem since the wires aren't faulty.

[jelan]

So I ordered replacement speakers and changed one out and nothing. I'm leaning towards thinking it may be the AMP but don't want to buy an AMP only to find out that is not the problem either. Is there a fuse that may be associated specifically to these two speakers not working? Are they on the same AMP channel? I only changed one speaker, do both need to be changed to work? Any additional insight would be appreciated!

[Smac770]

Jelan,

Did you swap the front and rear door speakers to see what still played when the speakers were relocated?

You mention 2011 but nothing about what sound system you are working with. US, so would be standard or B&O. The rear doors are wired the same in both case, though. Single amp channel and the wiring is split inside the door harness between the two speakers. So if one speaker in the door is working, then the amp channel is (likely) fine.

If the speaker works when plugged into the front door speaker plug, or works when hooked up to any amp stable at 2Ω, then you're left with the wiring, likely in the door harness itself. Which would seem odd to just go out randomly, in both doors, at the same time. But have you tested for continuity between pins 20 and 22 in the door harness plug and the pins in the door speaker plug? You could also test back to the plug on the J525 amp, the pinout for the amp is here in some thread.

If you just unplug the lower door speaker while the sound is playing, the upper door speaker should continue playing unchanged. Does it? Can you measure an AC voltage across the lower speaker plug when you play a 1kHz test tone? Is the value any different from the front door (this would be impacted by the sound system type), which you say works?

[jelan]

Smac770,

I did not swap front and rear, bought a used working pair of speakers assuming I had the same issue as Kobajs above. Replaced one speaker and nothing. It's probably not a speaker issue since the new one did not work as well.

I have a 2011 A4 Premium (B8) with the Audi Concert system. I looked at the wiring when changing out the speaker and it seemed fine, did not test for continuity. If I understand you correctly, all four rear door speakers (mid range and tweeters) are on the same amp channel so if the tweeters are working it should not be an AMP problem. Either way I found a used amp for cheap so I'm going to try swapping it out to see if that fixes the problem. One thing I found (that may be totally unrelated) is that a 15 AMP fuse in the trunk for the rear lighter plug was blown. I'm thinking that maybe when I used an air pump plugged to that outlet it shorted something else that's affecting those rear speakers. I will test for continuity at the door and to the amp.

Thanks for your help.

[Smac770]

Concert is the front end, but it doesn't say what speaker system you have. You either have the standard or the B&O, easy to differentiate by whether or not you have the 1" round rings in the door mirror sail cards for the B&O tweeters.

I said both speakers in the door are on the same amp channel. Left and right doors would be different amp channels. The amp channel goes to pins 20 and 22 on the door harness, where inside the door it splits between the two speakers. So if one speaker is working, then the amp channel to the door harness would seem to be fine.

As for swapping amp, you'll need to pay the dealer an hour to remove the component protection to know if that was your problem, as the amp won't play entirely correctly while component protection is active. Not sure what the CP exhibit will be on that, could be front left only plays.

[jelan]

So I have the standard (not B&O). Realizing that I probably bought the amp for nothing (just like the speakers). Did not realize I would have to remove component protection to replace the amp, just made sure I bought the exact same model and was going to do a quick swap. Any "simple" work around the component protection? The dealer is probably going to charge an arm and a leg and I'm not even sure the amp is the problem. Will test the continuity and try the rear speakers on the front door to verify it's not the speaker. Maybe the one I bought is bad as well and all I need is good speakers.

Thanks for all the valuable info.

[Tariqtash]

Was you able to solve this issue, I have the exact problem!!

[A4fuzz]

I'm going to attempt to revive this again... The "right rear mid-bass woofer" has shown an "open circuit" for a while now so I went about replacing the speaker with a used ebay one. This resulted in no change to sound output in that speaker. The tweeter still works but there is no sound from the mid-bass. This does not make sense, as noted several times above. I checked DC voltage coming out of the radio / amp unit and it seems that channel is weak or dead. I did not record the other channels readings exactly as I ran out of time but they were around 20 volts (maybe millivolts?) whereas the dead speaker was around 1 or 2 volts/mv coming out of the radio unit. This is a non-B&O MMI 3G. What would be a better way to diagnose the voltage / amperage using a multimeter tomorrow? I'm assuming the amp has a dead circuit or something. Maybe it is putting out just enough juice to make sound come from the tweeter but not the mid-bass.

[A4fuzz]

Well, I found my issue... The replacement speaker is junk. I swapped the other side speaker for this one and it works fine so its not an amplifier issue. I tested the old speakers on my home audio unit and got nothing, just like in the car. So for anyone having amplifier issues, I have nothing more to add to diagnosing that problem.