Issue When playing music there seems something wrong with the representation of bass by the two drivers for mid and bass. When it happens, the vibration sounds like there is something loose or damaged in the driver (foam ring, cone, dust cap). The vibration does not occur at low(est) volumes, but it starts to be hearable at medium volumes (and gets awful at higher volumes). These BeoLab 8000’s have serial numbers in the 1072 xxxx. These speakers had foam rot which has now been removed. All PCBs have been cleaned thoroughly. I have installed 1 bypass in the power supply section towards the relay. There was also quite a bit of foam rot sticking to the head side of PCB02 and PCB04. This has also been cleaned. I have not found any damaged copper traces (I hope I did not miss that). One speaker was free of vibrations for a while, after everything been cleaned and PCB04 had been placed back after cleaning. But the vibrations were there again the next day. Music (with bass) tested:

1. Vail Johnson – Bass solo (): Immediately from the beginning of the song, the vibration can clearly be heard. The vibration follows the kick drum instrument. NOT OK
2. Bass test 20 Hz ( Login to view image Question First I thought it’s the woofer drivers of BeoLab set 1 that caused the problem. Cause if they perform bad in a ‘bad’ BeoLab 1 set, but also in a ‘good’ BeoLab 2 set, it could be damage somewhere to the driver. But I was surprised to find that the ‘good’ woofer drivers from the ‘good’ BeoLab 2 set, performed bad in the ‘bad’ BeoLab set 1.
   1. A bit confusing now, because is this problem a combination of bad woofer drivers with a problem on the amplifier/cross-over filter side?
   2. So, what could be wrong here and what should I check?
   Any advice is welcome!   Attached:
   • Pictures of the ‘bad’ drivers from BeoLab set 1, after I removed them from the panel to have a visual check.
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