These bad-ass little speakers date back to 1983-84, intended to complement the Walkman line. They can run on a 6V adapter or four C batteries (not included). Even without power, they produce sound (Direct Mode).
This auction is for one speaker, but it is the most important one, as this is the one that connects to a headphone out. With a 1/8” mono mini plug in SP OUT, you can connect this to another APM speaker (or equivalent small speaker) and get stereo sound. Or you can just use it by itself for mono sound.
This is a vintage piece that is more about design and style than sound. There are plenty of small speakers today that will kick out much louder, bass-ier, cleaner sound. These are decent for the time they were made, but any little Bluetooth speaker will blow them out of the water. Still, they have a following, as evidenced by the pictured article from RetroThing.com.
This speaker has seen considerable use, but it still powers up and works properly. There are quite a few scratches on all of the surfaces, as you can see in the photos. The battery compartment is free of any oxidation or battery residue, but you can see that a good amount of the silver finish has been worn away to reveal the tan plastic below.
Sorry, but I DO NOT HAVE the other speaker, the power supply, the connector for a second APM speaker or the audio cable for a second speaker.
Single Sony APM-090 Amplifier Powered Monitor HiFi Speaker - Master Unit. Condition is "Used".