“Advanced Transmission Line (ATL). Unique to PMC it forms the core of all of our loudspeakers and it’s how they produce their impressively low, controlled bass, inherently low distortion and vast headroom. An extremely hard design to perfect we have to consider the length, cross-section, geometry of the transmission line as well as the absorptive material within the cabinet – it’s density, quantity and position in the line will determine it’s effectiveness at absorbing the unwanted high and mid frequencies from the rear of the drivers, so only the really low frequencies are produced from the transmission line. The transmission line is effectively another bass driver, so needs to be in phase with the rest of the speaker. This complexity is why most other brands choose the common, easier ported and sealed cabinet designs. It’s not easy, but when done right ATL won’t be beaten on linearity, bass performance and tonal consistency at all listening levels.”