About a month ago my HK amplifier stopped working, drivers speaker went first, in the end nothing,I removed the amp to find signs of water ingress dripping onto it, corrosion on the case and leaking through vent holes,I had to purchase a new amp and this is after BMW carried out the recall which consisted of a half baked plastic cover that dont even cover the whole amp and also the retaining tabs had broken off too ,anyway LTK came to the rescue with a new amp for me at a fraction of BMW's price, so a few weeks ago I set about making my own cover from sheet metal
BMW's inferior recall cover
New cover starts from this , 0.050" sheet aluminium
shaped to fit the amp
added a splash guard to stop water running down the sides
painted epoxy black
fitting it to the amp bracket
The boot vent in this photo is the main cause of water ingress I believe
Hopefully this should keep it dry and also there's enough space around it for the amp to cool/breathe