I've "tested" sweeps, bursts, kick drum, harmonic distortion, transient response, low frequency extension, (lack of) midrange audibility...the sub enclosure is acoustically inert! No extraneous noises from the enclosure or drivers. Everything sounds wonderful including music and movies.
Surprisingly there's a response at 1 Hz. Now mind you there's negligible SPL - just drivers moving. At 10 Hz though, the whole room is in motion.
I haven't cranked the gain knob - it's at factory default which coincidentally is perfectly calibrated for my room. Integration with the room and speakers was painless.
Based on what I'm hearing, I wouldn't invest any more in improving the acoustics of this sub.
I haven't hit the gut punch switch yet.