The lines between what one uses as a woofer and as a subwoofer are very blurred. Subwoofers are primarily designed to be used as "SUBwoofers" i.e. "below the normal range of a woofer". As such, you have to cross them over at a very low frequency and keep the upper and mid-bass out of them. Otherwise, you'll run into the two woofers ( mains and subs ) overlapping within a small frequency range and producing a noticeable hump in the response. This is especially true of a ported design, as the upper bass / lower midrange walks right our the vent from the rear of the cone. This can contribute to the "muddy" or "overpowering" effect that many folks tend to run into. Front loaded subwoofer designs will also tend to suffer from this, as you can hear the harmonic overtones coming from the woofers and this adds to your ability to "localize" the sound. Sean
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