bass suggestions 12 x 16 room....

For starters keep speakers out of the corners, and away from the back wall- these positions tend to reinforce bass, especially if the speakers have rear-firing ports. I have a similar sized room (11x13) speakers on the long wall. Speakers are just over 5 feet apart and 18 inches from the back wall, toe-in is one inch making them 19" away from the back wall on the outer corner. Listening position is about 6 1/2 feet back from the leading edge of the baffles. My speakers are pretty wide so yours may need to be further apart if they're tower type speakers. Placement can make mediocre speakers sound better than you'd think, and great speakers poorly placed will sound terrible. Experiment-I put blue masking tape on the floor when I find a placement I like so If I make a change it can be reversed if it isn't an improvement.

Hopefully, through positioning, you can reduce the problem to a narrow range of bass frequencies (ie. 50Hz-->60Hz) If it still bothers you, it might be necessary to change out the speakers for ones that roll off below about 60 Hz or use a parametric equalizer or low pass filter.

You may need a sound level meter, a tripod and some test tones (on a CD or otherwise) to fix these issues.

My room is 13x15. I stick to sealed box or front ported speakers. Could never get the bottom end under control with anything rear ported. And my room is well damped. Don't have the luxury of putting the speakers 4 feet from the back wall.

Wouldn't hurt to try some bass traps in the corners. Another thought, does your amp have adequate power for the speakers? The rest is all about speaker placement. Good Luck

You need bass trap pure and simple. This is your bottom line need and it will get you what you are looking for period. Buy GIK corner bass traps stacked floor to ceiling in your corners and you will be amazed.