What configuration and size enclosure is it? Is it a small sealed sub or is it a large ported (or passive radiator) sub? Sealed ones are good for blending with music but has limits on getting down real low such as during an explosion scene in a movie. Also, what is the power rating of it's dedicated amp? Stronger amp can push the driver through during demanding situations even on a sealed sub. Bigger sub isn't always the answer. You may want to try a different location first and see if it improves. Or try different crossover frequency. It is possible that the crossover is set too high and drowns out the mid. Without knowing more details of your sub, I can only give a rough guess.