Descent Subwoofer Problem

I have 2 Descent subs from Martin Logan. They are about 2 months old. The one sub went back for repair 3 weeks ago for a huming problem. I just got it back a week ago and I tried to play some deep bass music. The sub that just came back from the hum repair is rattling like the voice coils are hitting the magnet. The other sub is fine. They are both set at the same settings 5.5 on the volume and 3.5 on the 25hz knob.Dose anybody know what is going on with this sub? I will call Martin Logan on Monday and talk to Jim Power again. I just wanted to check with you guys if there is something I can do.

Did they tell you the hum was from the sub? What did they say they did to correct it?I have this sub and have never had any problem with noise of any kind. My settings are-Level 5, 250 at 0, 45 for the crossover. This is in my dedicated audio room with CLS11Z speakers. The room is quite large40x30x8. The hum may have been elsewhere in the loop,2 defective subs is more than bad luck.Check the screws on the woofers maybe they have come loose thru shipping, servicing or volume.
OK only has a problem with one sub.
My screws loosened up and rattled.Had other problems so I sold mine and found much better low frequincy producers for less cash.