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The first crystal and one -tube sets (1910-1923) could only power headphones. This made the choice of headphones as important as choosing speakers for a modern stereo.  Crystal radios worked best with very sensitive, high impedance 'phones (2 or 3 thousand ohms, as opposed to modern 4 or 8 ohm speakers, and 600 ohm headphones).  The Baldwin Type C, and 3000 ohm WLS 'phones (Figure 1) were much sought-after items.


Figure 1
As this limited listening to 1 or 2 people (sometimes 2 'phones were linked ), horn speakers became increasingly popular.  Why horns?  Because the horn structure allowed increased sensitivity by "coupling" the horn driver with the air in the room.  The "megaphone" part of the horn actually acts as a mechanical transformer, giving much greater volume.  Magnavox company got into the business early-- the first "Maggie" horns (called Telemegaphones) did not even have permanent magnets, but were battery powered horns which provided little sound until a battery was connected.   This 1921 horn is seen in figure 2.


Figure 2
Also in the early 1920's, headphone drivers were hooked to the horns, getting rid of the extra 6 volt battery needed to power the horn.  Figure 3 shows examples of RCA, Atwater Kent, and Jewett horns of the mid 1920's.  The tonal qualities of these horns were poor by modern standards, with audio frequency responses of about 1000Hz to 5000Hz, roughly comparable to modern telephone sound. 


Figure 3

Some "upscale" manufacturers tried to fold the horn structure to increase its size, and thereby improve the sound.  Figure 4 shows the inside of a Freed-Eismann speaker ca. 1925.


Figure 4
By 1924, the high sensitivity of a horn was no longer really needed.  The audio output of many radios was almost a tenth of a watt.  If you think of this in the current 100W/channel amps this doesn't sound like much, but the radio was only meant to be heard, not to rock the house.  With the audio power stages built into AK breadboards, and almost all 5 tube battery sets, the "drum" speaker came to be developed.  A few examples are seen in figure 5.  These are an Atwater-Kent model F, a common RCA, and an Atwater-Kent model E.  The model E comes surprisingly close to modern high fidelity, lacking only the deep bass of today's speakers.  The drum speakers, like the horn speakers, are all 1000 to 2000 ohm speakers, to match the '01A's of the era.


Figure 5
The amazing reproduction of the early speakers leaves one wondering why modern speakers are so lacking in sensitivity.  To quote a 1929 tube manual, "the type 10Y tube gives nearly 3/4 of a watt of power, for the most rigorous public address systems, to be used with rugged speakers."  Our early radio men did so much with so little.

Biographical note.  The author was born in 1954 and graduated from Eastern Michigan University in 1976.
He writes for Glass Audio, Audio Electronics, and Speaker Builder magazines.
to send Richard e-mail.

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