Acoustic and signal processing science has now reached a point where it is possible to effectively eliminate room resonances (also called modes) but also extend the low frequency reproduction into the infra-sonic domain. This course will look at the fundamental mechanism of room modes, introduce the latest active acoustics methods to eliminate them, and will give subwoofer placement guidelines for optimal performance. This course will also address the challenge of subsonic reproduction and how active acoustics can be adapted to extend low frequency range and increase SPL. The course will cover use cases and performance achieved in actual rooms: consistency of the frequency response over a large listening area and low frequency extension (to meet or exceed level 4 of the new CEDIA RP22 recommended practice). Reduced decay time over a large listening area, seamless integration of passive and active acoustics will also be discussed.