A correct car installation shouldn't thump your speakers. I can rip and jam my empeg in and out of my Carrera with wild abandon. A friend of mine has a thumping installation (more like a gunshot!). After swapping empegs and finding his car thumped with either, we took an empeg to the lab bench with a spare docking sled I happened to have laying around. We hooked up the RCAs to an amplifier which did not shut down in response to the empeg's remote line and found that as long as the yellow "Permanent power input" line was hot, you could flicker the orange "Ignition sense input" recklessly without a thump. If you connect the AC adapter or fiddle with the yellow wire, it thumps mightily. Interestingly, the yellow input is not necessary to run the empeg, but if you don't use it, you will get a thump when you light up the orange line. Hope this helps. Also check out Hugo's earlier posts on thresholds. Very interesting!

-jim