With the 1.5's, natural response of the rear drivers is flat-ish in response and does not need EQ. I don't think flat-to-20 hz is an expectation with the 1.5's but most folks aren't too concerned with that. They are crossed steeply above 40 hz and only an attenuator is available to adjust their output. A person could probably dig into the speakers and change that XO point/slope but I'm not adept enough to try it.
The Pro subwoofers are professional drivers, capable of significantly more output than the 1.5 drivers. However, their response curve is ragged and must be EQed. Without EQ, they run to 1 khz and fall off sharply from there.
With my TacT I can adjust the main XO point/slope as well as that for the subs. While a certain amount of shared output (bipole) is useful, i.e. shallow XO slopes, doing too much like running the mains down to 40 hz will muddy the sound. Further, getting the little main amp out of the bass zone makes it perform even better higher up.
The Pro subwoofers are professional drivers, capable of significantly more output than the 1.5 drivers. However, their response curve is ragged and must be EQed. Without EQ, they run to 1 khz and fall off sharply from there.
With my TacT I can adjust the main XO point/slope as well as that for the subs. While a certain amount of shared output (bipole) is useful, i.e. shallow XO slopes, doing too much like running the mains down to 40 hz will muddy the sound. Further, getting the little main amp out of the bass zone makes it perform even better higher up.