I just purchased a 2010 Mini S with the upgraded Harmon Kardon stereo system. This morning as I was driving to work, the sound system literally exploded. The loudest noise I have ever heard out of a car stereo. Every speaker in the car was screaming. I turned the radio off and the noise continued. It was so loud I had to roll the windows down and pull over to the side of the road. I turned the car OFF and the noise continued! Drove straight to the dealer where I bought the car and they imediately disconneted the battery. The noise stopped. They said that they had NEVER heard a stereo sytem make this hellish racket. They then re-connected the battery and the noise did not come back. They told me to just drive the car until the problem happens again. I told them that if it happens again, I'm calling a tow truck to bring it in. It's 3 hours latter and my ears are still ringing! My qustion is...Has anyone else experienced this? How the heck can the speakers have that kind of output, with the stero OFF AND the car turned OFF??

 

Can't even imagine what happened to cause the problem. But I can tell you one reason why it continued after you shut off the car.

The car computers do not go off right away after shutting the car down. They stay on for 15-30 minutes depending on the exact configuration.

Also the head unit is has the OBC (On Board Computer) in it and as such turning off the stereo only shuts off the radio/CD portion, and still functions for the OBC and warning systems.

So if you turn off the radio and shut the car off and the car is in some sort of warning mode it will continue to make sound for up to 15 minutes.

 

Thanks for the quick reply! This really has me concerned. There were no indicated warnings before or after this incident. Everything was running fine and then all hell broke loose. This million decibel racket did seem to be coming out of ALL the left channel speakers and MOST of the right channel speakers. As best I could, I checked all of the cars electronics (warning alarms, phone Bluetooth, radio/cd etc.) and everthing seems to be O.K. I guess I'll just have to drive the car and if it happens again, hope that I don't have a heart attck!

 

The same thing happened to my wife today in our 2011 R60 with the HK system. Did you ever have the problem again?

 

I have read at least one other person, with the HIFI system, have this happen a few years ago.

There is only really two places the noise could come from...The Amp or the Headunit and there is no good way to isolate the issue yourself.

But I would totally learn what fuse to pull to disable the amp (and or the head unit) if that ever happens again as that is bad for the speakers and bad for your ears!!!

 

The car is 1 year old now and so far, the problem has never happen again. I keep a 10mm wrench in the glove box (to disconnect the battery) just in case.

 

I suspect it has to do with the current-limiting circuitry in the amp. We've encountered the sound you describe when testing the power output of the factory HK & HiFi amps. To do that, we hook them up to a large resistor bank and drive them into clipping. On both the 1st Gen HK and 2nd Gen HiFi amps, at high output levels the limiting circuitry kicks in just after the waveform begins to square off and instead of getting normal clipping the whole thing goes berserk.

Sounds like something caused that to happen and for whatever reason the radio controls would stop it. The amp remains on as long as the RAD_ON signal is present - which continues for a while after the car is off - so it makes sense that turning off the car didn't stop it either.

 

Right after I posted I went out to the car and turned on the stereo. It played for a short time and began to smoke. It then stoped playing. It played again for a short time the next morning but was overheating and smoking. The car is now at the dealership waiting for an amp from Europe. I think because the seatbelt as well as other chimes go through the sound system, these amps are on whenever the car is on. This is the reason that the sound won't go away by turning the radio off, you would need to turn the car off.

 

When my sound system went crazy, the car had been shut off for about 10 minutes before the dealership pulled the battery cable and the noise stopped. Like I said earlier, It's been almost a year and I'm still keeping my fingers crossed that it dosen't happen again. For those of you who saw the movie "Spinal Tap", maybe I shouldn't have had the volume control at "11".

 

It was gone as soon as the car was shut down. It was ear shattering but then all was O.K. until we went back out and the amp smoked. Some sort of overload I am thinking. Just hope the HK isn't built in Japan, we need to get this puppy to Vegas next week.