My settings: 80Hz cross at receiver. +1.5dB gain for subwoofer setting at receiver and trim Flat. Bass out for subwoofer only.
Mine reciever is Yamaha 2500. Subwoofer volume at 9 o'clock.
The rattle sounds like "didi dada". I am afraid it is bottoming.
The subwoofer has been using 3 months.Most of the material do not generate rattle. My listening volume will never greater than -25dB.The movies have the woofer rattle so far are: War of the world, SkyCaptain, We were soliders.