<font color='#000000'>Try different placement within your room. Your sub is probably in a bass "mode", or an area in which the above said frequencies are amplified. Here is an equation to figure out your room's resonances.
Speed of Sound (1129 feet/ sec.)
____
Resonance (in Hz) = 2x Room dimension
(in feet)
You can use this to figure the resonance of the length, width, and height. This formula will give you the primary resonance for each dimension. Simply multiply by 1,2,3,4,ect. to find axial resonances.
Example:
Room is 15 L x 12 W x 8 H
Resonance L 1129/(2x15)=37.63 hz axials (75.26, 112.89, 150.52)
Resonance W 1129/(2x12)=47.04 hz axials (94.08, 141.12, 188.16)
Resonance H 1129/(2x8)=70.56 hz axials (141.12, 211.68)
You shouid be able to reaffirm this by using a handheld db meter from radioshack. These resonances usually will occur at the front and back of the room as well as other places. You should be able to find a bass node in the room as well with your meter. A node is actually a dip in frequency response. By placing your subwoofer in a node on a wall that does not accentuate the frequencies you are having a problem with you will help to tame your rooms resonances.
Get your room dimesions and go to
http://www.guidetohometheater.com and click on "The Sweet Spot". There is a free program that can calculate all of your rooms modes and node peaks and nulls and help you place your sub properly.
References: Stereophile Guide to Home Theater July/August 2003, December 2003</font>