The problem with typical bass reflex tubes is their own quarter and a half-resonance wave (as in fife) which affects the final characteristics of the loudspeaker and more or less distorts it. The unique proprietary solution that we called PWaveBass© (Perfect Quarter and Half-Wave Bass) allowed us to develop a new bass reflex pipe with an appropriate chamber that suppresses its own quarter-wave resonance and a second one, that suppresses half-wave resonance.
The graph from the measurements of the bass reflex pipe radiation shows two waveforms. Yellow line is typical for a classic tube with visible strong resonance at about 600Hz. The second line is solution with a damping chamber. You can observe damping 30dB obtained, which is an unprecedented result.