Setup #1. In my upstairs system, Michael's MusikBass could go right between the monitors. Then it would simply aim its rear output directly at the components and counter the rack's efforts at silencing them. Having repeatedly gone on record just how effective HifiStay's X-Frame rack is at heightening resolution from broad-band resonance attenuation particularly with a subwoofer in play—spot our big Zu Submission optimally loaded in the left corner—that felt counter-productive in the extreme. I'd start by putting the sub in front of the right corner table toed directly at the listening chair instead. Now the rack would see the sub's lateral null for minimal bass exposure. With the active filter in my autoformer preamplifier, all I needed was a powerful amp to drive the new sub.
Hello Kinki Studio EX-M1. It's a high-bandwidth class AB Mosfet integrated of 215wpc/8Ω with dual-mono linear power supplies and damping factor of 2'000. This was my classiest sub amp on hand. Its remote would adjust the sub's volume independently. The preamp's remote could turn the sub feed on/off from the chair. Our usual 25wpc Bakoon AMP-13R would drive the satellites and share its class AB-biased Exicon lateral Mosfets with the Kinki which uses them too.
Those sound|kaos Vox 3wf are ultra compact 4-driver 3-ways. Their horizontally opposed carbon-fiber woofers are good to ~35Hz. The preamp's high-pass slope starts its kink at 100Hz to be -6dB down at 40Hz, -24dB at 20Hz. The sub does the exact inverse. The speaker's natural reach gets cut just slightly but the woofers no longer see any low bass. That keeps their voice coils cooler and their impedance lower to open up mid-bass dynamics. The obvious proviso? I had no shelving boost to compensate for the RiPol's 6dB/oct. fall-off. Logic predicted that the Zu would have more linear output all the way down. Boost would have to wait for the Gradient Box since Axel Ridtahler's own external crossover box with such a boost profile was discontinued. The Gradient Box was provisionally spec'd for four profiles of +3/+6dB at 20Hz starting at 80Hz or 160Hz and would probably drop late Q1 of 2021.
Here's a look at Michael's dedicated TruAudio bass amp with remote-controlled filter settings. For a starting point with it, I checked with sound|kaos designer Martin Gateley on his acoustic roll-off and where it kicks in. Usual sealed designs roll off at 12dB/oct., ported variants like his at 24dB/oct. Knowing slope and frequency of our monitor speakers would determine the best setting for TruAudio's filter. In augmentation mode, it had to limit the MusikBass to just the very narrow bandwidth outside the speaker's own grasp and do so at the matching gradient. The published -3dB spec for the Vox 3awf was 35Hz.
Now I had all my 'i' dotted. How would velocity dipole bass compare to our usual pressure box bass? Raise the curtains!