B&O rear deck subwoofer cuts out in B9 S4

[toxicxk23]

Just picked up a new to me 2018 S4 last month and I'm noticing some audio issues. Some times I notice that the subwoofer in the rear deck stops working. It's noticeable as the bass drastically drops. If I mute (or turn off?) the audio system by pressing down on the volume knob and then turn it back on, the bass from the subwoofer comes back. This happens with the sound effects features on or off. Has anyone experienced this before? FWIW, I do currently have the front passenger woofer unplugged as it rattles with low bass. Haven't decided whether I want to replace it with another OEM sub or follow the B&O speaker upgrade guide on this forum and swap it out with better quality ones. Could this be causing the rear deck sub to cut out? I'm not much of an audio guy so I don't know much about the system.

[Bobby Kinstle]

You need to add a pair 50 ohm load resistors to the subwoofer wires where it feeds into your LoC or change to an LoC or amp that has load resistors in it. My LC2i worked fine for almost a year and then I started having the exact same problem. The KISLOAD from Kicker is a clean way to do this, or you can buy a couple big chunky power resistors on Amazon

[bruce_miranda]

@toxicxk23 do you have just the OEM subwoofer, or an after market subwoofer and amplifier?

[toxicxk23]

You need to add a pair 50 ohm load resistors to the subwoofer wires where it feeds into your LoC or change to an LoC or amp that has load resistors in it. My LC2i worked fine for almost a year and then I started having the exact same problem. The KISLOAD from Kicker is a clean way to do this, or you can buy a couple big chunky power resistors on Amazon

Thanks Bobby! I saw your picture on AudiWorld. Do you possibly have a picture of where it's connected in the car or where I would need to mount the resistor? Seems like an easy task for me to do on my own just don't know what I'm supposed to be connecting it to since I don't really know much about audio. Is there a fix that a dealer could take care of under warranty? I might be bringing my car in to have them replace one of the door subs. Maybe they can fix the subwoofer too?


@toxicxk23 do you have just the OEM subwoofer, or an after market subwoofer and amplifier?

OEM

[Bobby Kinstle]

Thanks Bobby! I saw your picture on AudiWorld. Do you possibly have a picture of where it's connected in the car or where I would need to mount the resistor? Seems like an easy task for me to do on my own just don't know what I'm supposed to be connecting it to since I don't really know much about audio. Is there a fix that a dealer could take care of under warranty? I might be bringing my car in to have them replace one of the door subs. Maybe they can fix the subwoofer too?

The dealer won't touch this with a 10 foot pole. In fact they will threaten you with voiding part of your warranty if they find out about it.

You need to connect each resistor across the + and - terminals of each subwoofer channel from the car. I did mine at the input terminals on the LoC. You can do it there because it's probably the easiest, or you can connect up top where the factory sub connection is. It will get warm but not hot enough to worry about. That heatsink I used is massive overkill. Adding the resistor will create enough load to stabilize the factory amp and keep it from shutting down it's output channels.

[bruce_miranda]

If you just have the OEM subwoofer then I do not think you should attempt the fix that Bobby is suggesting. His fix is for when you connect an after market amplifier and it exhibits a similar symptom to what you are seeing. I think you need to visit a dealer.

[Bobby Kinstle]

Yes that's correct, I assumed you have an external subwoofer amp. If the problem is with the stock sub and stock amp, take it to the dealer under warranty.

[toxicxk23]

If you just have the OEM subwoofer then I do not think you should attempt the fix that Bobby is suggesting. His fix is for when you connect an after market amplifier and it exhibits a similar symptom to what you are seeing. I think you need to visit a dealer.


Yes that's correct, I assumed you have an external subwoofer amp. If the problem is with the stock sub and stock amp, take it to the dealer under warranty.

Yeah, all stock. Car is going in on Friday to have them check out my front passenger door sub. Sounds blown. Will be telling them to check out the rear sub cut out issue and the crazy rear deck rattling.

When I called the SA about it, he was a bit stand offish when I told him about the blown door speaker and was like "yeah, I'm not sure we'll cover that under warranty but we'll see".

These are some of the issues where I gotta decide if I gotta waste my time with the dealer and make the repairs/upgrades myself since I've always worked on my own cars. However this is the first time I've had one with warranty left on it (about 12 months/6k miles left). *sigh*


Bobby,

Do you know what causes this cut out? Is it the amp itself failing over time? Seems like some pooor quality if that's the case... :(