Poor room acoustics causing an emphasis in the 40-60 Hz region.
A poor FR from the sub itself, with an inherent emphasis in the 40-60 Hz region. High distortion from the sub can also add audible harmonics in this bandwidth.
A wooden floor over an open space (like a basement), which can flex and resonate and add sound.
Agreed. One of the reason that people recommend putting subwoofers in the corner is that they excite the most resonances in that position. I had a +18 dB peak at 40Hz in my room and it sounded impressive initially but I realized that it was at the cost of true deep bass. Getting a parametric EQ has helped.
Thanks for the info. I just moved my sub. to a corner position from a center wall location and the sub certainly sounds louder. I haven't done a check with the meter to see if I have any problem at certain frequencies. BTW, I have a DVD that does a frequency sweep but where can I get one that plays and holds at certain frequencies? Also, if I have peaks at certain frequencies what would be an acceptable peak as compared to other frequencies?
That's what my current location is like. If I was to move to the basement below would the problem still exist since the resonating floor is just above now rather than below?
Ned, if you moved the rig to the basement, the bass would probably tighten up considerably.
The air pressure would not be enough to flex the wooden ceiling in the basement; it is the direct reactive forces of the woofer which create the floor boom.
I agree with Felix - an A/C paver for $10 should help considerably to decouple the sub from the floor. If you want something fancier, I'll put you in touch with someone who makes them from marble.