I am experiencing the same problem. I am also about to replace the DMTL...which seems like a completely unrelated issue, but read on:
Someone posted in this or another thread on speaker static that one cause of the static might be water below the amp, which is in the left side of the trunk. He did not know how the water got in. Well, read on.
Another post said he unplugged a cable from that amp to end the trouble.
So...I checked for water around the amp. The area was indeed wet.
I did this while searching for the DMTL, which some said was on the right side, some on the left, but the descriptions made me think it was forward of the wheel. Well, I finally located it: It is BEHIND the rear left wheel on my vehicle, RIGHT BELOW THE AMP.
And below the DMTL is a splash shield. Mine has a huge hole in it.
SUMMARY:
Splash guard badly gored.
DMTL current bad; plug exposed to violent splashing.
Amp area wet; right above the splashing.
No way to prove this, but a possible cause of DMTL failure (which seems to be common among these models) AND the speaker static is a damaged splash guard below, allowing powerful water splashing to fly upward.
Your mileage, of course, may vary.
BTW: Got the DMTL from
http://www.eeuroparts.com/Parts/2934...p-16137193479/
Price was $118 with regular shipping; I added overnight for $29.99
One other place had it cheaper ($103) plus shipping, ending up with about the same price.
BMW Riverside Calif quoted me $194 and change for the same part.