<font color='#000000'>Hi
Standing waves are created and are a direct result from room dimensions
Mode overlap is a result of the ratio of the room dimensions
and the impact of room modes will be determined by how dense the wall are You have three types of wave modes
Axial, Tangential and Oblique Axial are the most important and occur between two opposite walls Tangential occur between two pairs of walls Oblique occur between all room surfaces
When the frequency increases the room modes smooth out and become more evenly distributed 135Hz is generally
the frequency where the FS becomes diffusive. Room Modes
can't be eliminated so you have to work around them to try and minimize standing waves There are a few ways to do this
#1 Move Listening position #2 Move Subwoofer Location
#3 Use Absorption #4 Active EQ
Subwoofer placement is the easiest solution as a general rule placing the subwoofer 1/3 in or along a wall will give you the smoothest response these are generally the Low relative Pressure locations in a rectangular room another consideration is to find out where the subwoofer drives the positive and the negative areas of the wave between your listening position and the subwoofer place the subwoofer in-between the positive (hump) location of the wave and the negative (dip) location and this will reduce resonance Or get two subwoofers and place one at the positive location of the wave and one at the negative location and drive the positive and negative locations of the wave equally. Moving your seated listening position is another way to minimize the modes placing the seated location between the positive location of the wave and the negative location of the wave will reduce resonace.Absortion is another way to reduce standing waves however you would need very thick absorptive material absorption at 90Hz would take approximately 4 feet thick absorptive material. Active Equalization is another way to reduce standing waves but formulas and room calculations are complex and you may end up minimizing standing waves at the expense of creating other problems in the room This should not be done unless you are qualified to do so
Hope this helps
RLA</font>
