Posted by Wayne Parham on April 18, 2003 at 23:40:36

In Reply to: Re: Phase of active and passive filters posted by Adrian Mack on April 18, 2003 at 22:04:11:

A port in a bass-reflex loudspeaker cabinet forms a Helmholtz resonator. It acts very much like an LC tank circuit. Since the woofer is also a resonator and its frequency is close, the two systems are tightly coupled.