The Procella V6 subwoofer extending below 18Hz (bass module for P28)
Invision ISE 2020 Home Cinema Demo Features Procella Speakers, Trinnov amps, Sony 4K Projector and Kaleidescape Movie Player | StereoNET United Kingdom
Procella Audio Has 𝙃𝙐𝙂𝙀 Subwoofers! - YouTube
Procella Audio V18 Dual 18 Inch Subwoofer Preview | Audioholics
P15 Tech Sheet v2.1.pmd - D | Manualzz
Subwoofers Archives - Procella Speakers
Procella Audio manufacturer of Home Cinema Loudspeakers
Deep bass extension makes the P12 a true subwoofer compact subwoofer.