Recommended by Eguth, I hereby paste some additional Wireless World items by/about PGAH Voigt, in order to further build this reference:
W.W. Dec. 10, 1921, p.560-562, Article: "Simultaneous high and low frequency amplification".
W.W. July 21, 1933, p. 43, Trade note: Voigt manufacturing is moving.
W.W. Mar. 15, 1936, p. 308, News: Voigt 4ft square horn.
W.W. Apr. ?, 1936, p. 350, Letter: Shutdown of the Little Nationals transmitter.
W.W. July 17, 1936, p. ?, News: Voigt outdoor PA speaker (P. Voigt? hosing down speaker w. mains applied).
W.W. Aug. 28, 1936, p. 201-202, Article: "Cabinet or baffle ?" Discussion of resonance vs. Voigt domestic horn.
W.W. Feb. 15, 1937, p. 139, News: Voigt PA speaker.
W.W. Aug. 6, 1937, p. 127, Advert./News: Interesting cabinets. Display of Voigt/Lowther special order, beautiful system.
W.W. Oct. 15, 1937, p. 390-392, Letter: "Mr. Voigt replies" (Again, more thorough reply of transient reponse, a "thread" of many reader letters).
W.W. Aug. 25, 1938, p. 103, Advert.: Voigt speaker demo during audio show.
W.W. Sep. 15, 1938, p. 103, Not Voigt, but Lowther, showing beautiful, massive "reciever" with all bells and whistles, looks like a marine radio.