Reverberation Vs Pressure - www.AcousticFields.com

A room is a box full of pressure and reflections. Energy below 100 Hz. is always trying to leave. If it can't leave, or most of it anyway, it stays within the room and expresses it's discontent through room modal issues. Low frequency pressure must be managed through the use of absorption. Middle and high frequency energy can be managed through the use of absorption or diffusion.

[Castilhox]

In my room, I have found that pressure related unwanted energy goes around bellow 125 hertz. And man... After building eight diy BDA units, it became so simple to treat the rest of the spectrum because i really had to focus just on 100hz and above.