Older stereo speakers operate in the same manner, and with the same theory as modern speakers. While significant advances have been made in materials and cosmetics, fundamentally, the core physics haven't changed. Connecting older speakers to newer amplifiers and receivers is quite simple and intuitive. In fact, advances in speaker adjustments in modern surround receivers make compatibility even more likely, making vintage speakers easier to integrate with modern gear.
Strip off any old speaker wire that may be green or brown with corrosion. If the speaker wire ends have RCA jacks -- and the new receiver doesn't incorporate those -- cut them off.
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Strip back the speaker wire approximately 1/2 inch. Separate the two wire halves.
Twist the bare wire to prevent stray leads. Untwist the binding posts on the receiver or amplifier, exposing the post holes.
Insert the bare wires into the post holes. Place the wire with the stripe or writing on the jacket into the red, positive terminal. Twist the posts back down to secure.