English: Giant horn loudspeaker at Berlin Radio Exhibition. During most of the 1920s, radios ran on batteries, and the early vacuum tubes could not produce much audio power. So the first loudspeakers, used with the first vacuum tube radios were horn loudspeakers, because the horn was more efficient. Horns can produce 10 times (10 dB) more sound power from a given audio signal than the later cone speakers. However ordinary-size horns have a high bass cutoff frequency and so cannot reproduce bass frequencies, so they sound "tinny". This is a "high fidelity" horn speaker, large enough so it's bass cutoff is low enough to allow more natural reproduction of concert music.

Original caption: Interesting curios at the radio exhibition at the Imperial Dam in Berlin! A giant speakers on the issue.