Shadorne gives good advice. Measure the frequency response if you can.
IMO, it's possible you have a room mode that is resulting in a cancellation at approximately the same frequency as the missing bass notes. It's a little strange that the result is *constant* across the entire room, but I think it's still possible that the explanation is a destructive room mode.
If you cannot measure frequency response, the next step might be moving the speakers to new positions around the room, even extreme positions, to see if ANY change of placement can make the undesired effects go away. If you can make them go away with room placement, then you can conclude that it's a speaker/room interaction. If not, at least you've ruled it out.
Good luck.
Bryon
IMO, it's possible you have a room mode that is resulting in a cancellation at approximately the same frequency as the missing bass notes. It's a little strange that the result is *constant* across the entire room, but I think it's still possible that the explanation is a destructive room mode.
If you cannot measure frequency response, the next step might be moving the speakers to new positions around the room, even extreme positions, to see if ANY change of placement can make the undesired effects go away. If you can make them go away with room placement, then you can conclude that it's a speaker/room interaction. If not, at least you've ruled it out.
Good luck.
Bryon