Try this test.
If you have a SPL meter, go to that scene again and play it at a lower volume. Read the meter. Now play it again and again while increasing the volume. You should see the SPL meter increasing at the peaks at an equal amount. Once you start to see the SPL meter not increasing while you are increasing the master volume, you know your are reaching the limits of your sub. At this point if the volume level is not acceptable to you, you have two choices. 1) You can lower the level of your sub so you can increase the overall volume, or 2) Upgrade your sub.
