I have a 2 channel set up w/ the occasional sub. I had SL3's for 20 yrs and picked up 11A's last summer. Wonderful speaker.
Suggest you check with ML support for suggestions about troubleshooting. Also work your way through the signal chain to make sure the problem is not upstream.
So, it starts. Three years from now he will have a Dynamo 1600 with two Masterpiece 11A's. A killer ML center channel and two ESL's for surrounds! The ML disease is like diabetes, it can get expensive! The worst part is once people are diagnosed with Martin Loganitus, they don't want to be healed. They love wallowing in the disease with others........