@dynamiclinearity Part of the problem is most sub woofers only have a low pass filter to roll them off where they mesh with the main speaker. If they also had a high pass for the main speaker to reduce the load on it, then the small main speaker could play much louder(and improve its performance and openness and clarity in the range above the high pass.
The original poster’s remote controlled Velodyne Digital Drive-15 is equipped with both variable low and high pass filtering. All Velodyne DD series subwoofers offer the ability to act as a master Optimization control in conjunction with most any slave subwoofer.
High pass filtering is not a panacea rather a method to be tried. Usually in the case of inadequate amplification power to the main speakers or if the main speakers provide a poor low frequency response at their lower limit. In any case high pass filtering is a trial and error option to be determined by the user.
@ghdprentice If you have a budget system and want to get the best and coherent sound (matching a two way with and 18" subwoofer is going to be hard)...I’m just guessing this is not a $12K subwoofer.
Using the original posters remote controlled Velodyne Digital Drive-15 provides multiple adjustment parameters for matching the main speakers presentation as well as room optimization and equalization which are then saved to six memory presets. Velodyne DD series subwoofer’s position must first be determined by using the subwoofer crawl or their calibrated mic while noting the rooms strongest or best sound standing wave modes (as should any subwoofer) to position the subwoofer in.
The Velodyne DD Plus series uses a more in depth twenty minute auto program to make these adjustments which can easily be manually altered to taste then saved to memory within either models six EQ presets.
Velodyne technology eliminated the "hard’ twenty-two years ago for either 10" $2,500. to 18" $5,800.