I auditioned the DefTech SuperCube Reference at a dealer using source material that had sustained fundamentals (from pipe organ foot pedals) ranging from 32Hz to 16Hz. 32 Hz was extremely powerful, but by 16Hz, I would say that the power had pretty much fizzled out. I would personally call shenanigans on their claim of 11Hz extension. There may be measureable output at that frequency, but not at any useful SPL.