I would bet it's room/speaker positioning. I once moved a tall record rack to the other side of the room...right next to the left speaker at what would be the 1st reflection point. I thought bass was fine before, but it was like all frequencies came into focus...tighter, including bass. I had good bass before this change but now it seemed as if the bass frequencies were punching at exactly the same time...so impact and clarity was improved.
Wasn't even my idea either...wife needed space on the right side of the room. It is not hyperbole to say it was a night and day difference.