I have the same problem with my KMT6s. They are pushed by the ZXM450.2. My cabins and sub are being pushed by the ZXM700.5. They are both ground to the same point. The only difference is that I have a PAC volume control to control the volume of the towers. I’m pretty sure the problem lies with the PAC. The installer suggested to try “jiggling” the RCAs on the back of the PAC…yeah…ummm that didn’t fix it. If the PAC is all the way up or down and the motor is on there is no whine. However if the level is anywhere between there is. I’m sure it has something to do with how the RCAs were run for the PAC but I don’t see a power wire or anything like that near the run that would usually be the cause of this. Oh well I’ll figure it out eventually.