Heres a copy i have of it (archive)

"If you suffer from small to quite moderate vibration in your H/K speakers, please try this. I just took my car to the dealership and they shoved insulation into what wasn't causing the problem. I finally found the old fix for it and did this just minutes ago. I'm partially quoting the old solution. FYI, I have a 2000 coupe.
I got fed up and decided to dissect the HK subwoofer module in the trunk. It is held snug against the top of the trunk compartment by 4 8mm fastening screws and 2 plastic pins.

After removing the screws, the sub module loosely held by the 2 white plastic pins. with one smooth motion, slide the module down and towards you (assuming you are facing forward the front of the car). I just broke the two plastic pins bec ause carefully removing them isn't easy plus they are NOT needed. I snapped off both of mine and it sounds great.

Once the sub module is removed, take care not to overstretch the wires from the crossover/amp. Put something under the hanging speakers to lift it high enough to give slack to these wires.

You should see two 5-6 inch cutouts in the top of the trunk which the module originally covered. The portion of the rear deck that rattled the most was near the portion of the deck closest to the back window, about 5 inches behind the center cargo fastening anchor. From the trunk, your best bet is to stuff 6 socks in the center section (between the 2 large cutouts) and pack them all along the middle going towards the rear seats. Take care to put upward pressure against the rear deck. If you do it properly, you should be able to see the rear deck move slightly upwards in that area through the rear window. Before screwing the speakers back in, go in your back seat and press down on the back of the rear deck. Get that as tight as you can. It is what is soley causing the vibration.

If you like, you can find other areas through the 2 cutouts that allow a good point to put dampening material (i.e. socks) in the dead space between the rear deck and trunk compartment metal. I did not and I hear no vibration.

When complete, slide and mount the sub module (note two 3/4 inch tabs that fit into notches in the trunk metal). Re-fasten the 4 screws.

Now find some bass-pumping music and turn it up....no more rattles. For good."

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