In Reply to: An attempt at an answer... posted by mollecon on September 12, 2003 at 14:03:08:
The most succinct way I can describe bass-reflex behavior is to say that the Helmholtz resonator has influence between fb and fh. It reduces cone excursion between fh and fb and augments bass output between fb and fl. Ported systems can generally be made to have a lower cutoff in a smaller box than sealed systems.The terms fl, fb and fh are discussed further in the posts called "Behaviour of vented loudspeaker systems" and "Measure impedance."
About group-delay and phase, remember that higher-order filters have greater phase shift and therefore more group delay. What this means is the faster the rolloff slope, the higher the group delay. A 24dB/octave rolloff has greater group delay than a 12dB/octave rolloff. That's just the nature of filters.
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