I would try the ATC speakers crossed over between 65-75 Hz with a 2nd order Butterworth filter on the miniDSP. The sub should be crossed over at 65-75 Hz with a 4th order Linkwitz-Riley type crossover.- either in the miniDSP, or using the subwoofer's own crossover (assuming here the sub has a 4th order low-pass cross over option). The idea is for the ATC's natural roll-off and that of the miniDSP to combine together. The combo will be equivalent to 4th order and close to a Linkwitz-Riley alignment. (If you have a home theatre processor, this can also be achieved by setting the ATC's to small.) Start with the polarity of both the ATC and the sub as positive. Depending on where you locate the subs relative to the ATC, you may also need to play with the phase adj knob on the sub if it has one.
How do you high pass your main speakers?
I have been very happy with the distributed bass array I added to my system, but from what I hear, the optimum method of integration is to high pass the main speakers.
Two questions:
1. What are my options for accomplishing this? Does this need to be a feature built into my amplifier or is there another component that needs to be inserted in the chain.
2. What crossover point would be ideal? What frequency and amount of rolloff would be best if my speakers are ATC SCM19's which have a frequency response of (-6dB) 54Hz-22kHz.
Cheers,
Tony