In the very early years of radio, headphones was about all there was for sound reproduction. The horn speaker became the norm in the late teens. Most early horn speakers consisted of a sound magnifying horn with a what was not much more than the sound element of a headphone attached to the base.
When you purchased your new radio in the early 1920's most of them did not have enough power to drive a loudspeaker so headphones was how you listened. Many companies offered one or two stage (some had three) audio amplifiers that would amplify the weak audio sound enough to drive a load speaker. These (amplifiers and loudspeakers) of any brand of could be attached to the simplest of radio receivers (even crystal sets) so the whole family could listen.
Loud speakers were usually an option and if desired were purchased separately. Most all permanent magnet speakers of the 1920's had an impedance of around 2000 ohms. All permanent magnet (2 wire type) speakers were compatible with any radio of that era that could drive a loudspeaker. This applies to both the horn and disc type speakers. The disc (or cone speaker) were introduced in the mid late 1920's and were compatible (and proper for use) with any brand 1920's radio. This applies to either battery or the early AC sets. The exception was some of the AC operated sets made in the late '20's required an electrodynamic speaker (more on this type later). It was quite common to have a radio of one brand and a speaker of another as many speaker companies did not make radios and some radio companies did not make speakers. It is proper and ok to use any radio - speaker combination of that era as few sets came with a speaker unless it had one built-in or a combo pack was offered. There were a few (very few) speakers designed (cosmetically) to go with a particular radio, an example was the RCA Radiola 33 receiver that was sold with the Radiola 100B speaker.
Speakers with 3-4 or more wires were
usually designed electrically for a particular set and almost always
had a special plug that plugged in to the radio chassis. These type
speakers were not usually compatible with other radios.
You should never apply power
to a radio with a proprietary speaker
(electric sets) without the speaker connected. Doing so will
almost always result in damage to the radio's power supply.
These 3-4 wire speakers are "electro-dynamic",
that is their magnet is energized by a coil (this is called the
field coil) which is part of the power supply circuitry of the
radio. A good example of this type is the
Kent 55. Speakers with only 2 wires will have a permanent
I am often ask if these early speakers can be operated from a modern radio or amplifier, that answer will be found on my Tech Tips page.