The proposed workshop/tutorial serves as a prequel to the presentation on the history of dynamic loudspeakers given at the 158th Convention (Warsaw, 2025). It focuses on the earliest phase of consumer loudspeaker technology in the 1920s, prior to the widespread adoption of dynamic loudspeakers in the mass market.
Loudspeakers had been in use since the mid-1910s for public address applications, and the rapid global expansion of broadcast radio soon brought loudspeakers into domestic use. The 1920s constituted a period of rapid innovation in loudspeaker design, preceding the introduction of the dynamic loudspeaker, which achieved significant commercial impact only in the latter part of the decade.
The workshop/tutorial will examine consumer loudspeaker technologies of the 1920s, the concurrent advancements in audio electronics and signal sources that enabled subsequent developments, and the earliest efforts in systematic loudspeaker theory and measurement.
Two loudspeaker types dominated this period: horn loudspeakers driven by electromagnetic drivers similar to those used in headphones and telephone receivers (with headphones, particularly Baldwin models, also serving as the basis for do-it-yourself loudspeakers), and open-baffle cone loudspeakers, frequently actuated by electromagnetic reed drivers.
Although these transducer technologies were rapidly superseded during the following decade, the electromagnetic loudspeaker era already featured multi-way loudspeakers employing passive crossovers. Early measurements exposed deficiencies in frequency response, leading to the introduction of equalisation techniques, including notch filters, to correct these responses.
Developments in amplification were equally significant. The 1920s saw the introduction of push-pull amplifiers (described at the time as “distortionless”) and, as a key contributor to improved bandwidth and reduced distortion, new audio transformers derived from Bell Labs’ telephone research. Amplifier power limitations nevertheless remained a dominant constraint in loudspeaker design, resulting in the widespread use of strong resonances to achieve high sensitivity. Improvements in signal source quality from the mid-1920s onwards — including advances in radio transmission and the introduction of electrical disc recording and playback — further increased the demand for improved loudspeaker performance, ultimately contributing to the development of dynamic loudspeakers. In contrast, headphone technology appears to have undergone relatively little development during this period.
The tutorial will conclude with a brief overview of the loudspeaker manufacturing landscape of the era, noting that only a small proportion of manufacturers survived the transition to dynamic loudspeaker technology.
