It's just too light in the bottom end. The EXP changes all that. Enjoyment improved immensely. Played through the 5 and 10S alone, there is startling clarity and definition, with an image so carved out in space it's almost spooky. With EXP in play, the vocals retain the same type of clarity, but there is more presence and spaciousness through the improved resolution of the bottom end.
Drums have much better weight and presence, and the room ambiance is conveyed more convincingly.
I find that although this too can add weight to the music, it can obscure detail and not be a positive thing. While other subwoofers in its price range can go deeper and play louder, the EXP is on the money with solidity and control and proves ideally matched to NSM's speakers. In fact, with both the NSM 5 and 10S, there was no doubt that things improved all around. Gaining bass extension like that which the EXP offers provides a clearly audible improvement, far more than spending a similar amount of money on cables or the like. There is just no guessing that you may have heard an improvement when the frequency response is obviously extended.