@mijostyn IIRC the Dayton Audio amp that Duke LeJeune recommends for his swarm has a high pass filter but it's fixed at 12 dB per octave. So not very flexible. It's why I decided to use my own active crossover for the swarm I put together.
Building Resonance Free Subwoofers
Rotator cuff surgery has left me with enough disability time to complete the picture diary of the construction of MS Tool and Woodcraft Model 4 passive subwoofers which many have asked for. Here it is https://imgur.com/a/dOTF3cS
Feel free to ask any questions. It will help fight off the boredom.