This paper describes a Progressive Wave System, 1 in. × 1 in. in cross section, employing one electro‐pneumatic transducer in the frequency range 37.5–1200 cps. The unit is capable of generating sound pressure levels in excess of 160 db over‐all sound pressure level. High‐frequency energy is generated by conventional compression‐type dynamic transducers. The high‐frequency energy is combined with the low‐frequency energy in a mixing unit which consists essentially of a 45° acoustic mirror. By means of appropriate slots, the mirror is made transparent in the low‐frequency range and reflective at the higher frequencies. Design data on the acoustic mirror and measurements of over‐all and octave band sound pressure levels, as well as variations in sound pressure over the cross section of the tube, particularly in the transition range from the plane to the progressive wave condition, are presented. The capability of the system when four electro‐pneumatic transducers are employed also is discussed.