Your sub woofer is probably ok but I could be blown. The '07 thru '09 ML system had an amazing deep bass sound even if the bass adjustment wasn't in top notch position. The sound is different because the bass isn't as strong in the newer models and its obvious if you had a '07 - '09. Just check all your adjustments and make sure the sub woofer is working because its the only speaker located in your trunk.