I have a REL Q150e mkII which I got about 8 months ago. I'm experiencing a problem with it but I'm not sure if it's a genuine fault or the limitations of the sub. The problem is that at certain frequencies it starts to rattle!! This has been like so since I got it which is why I keep thinking it's not a technical fault. The first couple of months I thought it was something else in the room that was rattling but when I put my head next to it I realised it was the actual sub. I've been putting up with it because it only happens for certain effects (I guess very low frequencies) where the effect lasts for more than 1 second. A good example is near the opening credits of The Fifth Element, before the spaceship comes into view, there is a nice low rumbling sound as you hear it approaching, but as soon as it comes into view, the sound goes even lower and that's when the sub starts to rattle. I have it connected to an AVR300 with the crossover on the amp set to 70Hz and the volume on the sub at around 40%. The mode switch is at 2 (LFE/0 degrees phase/crossover bypassed for LFE). The Slam/Depth switch is at Depth. I'm also using the high-level input connection and the hi-level volume is again at 40% and roll-off set at around 40Hz. So the settings are quite modest, not too high. I even experimented with turning the low-level volume all the way down (during the Fifth Element scene) but it still kept rattling . Do you think it's a fault or my settings, or is it cause the sub can't cope with the very low frequencies?