With the rise of cassette tapes, the steady phase-out of bulky vacuum-based amplifiers, and the advent of in-car stereo set-ups (as opposed to single-speaker, monophonic systems), the 1970s also saw the beginnings of what is now known as the aftermarket—the sect of the automotive industry involved with parts and accessories after the initial sale, allowing car owners to customize their cars themselves. Custom stereo outfits started to become a popular option for drivers who wanted systems with more power than cars originally came with. Companies began to sell pull-out cassette receivers and higher-quality speakers that drivers could install themselves.
Breakthroughs in the quality of car sound systems during the 1980s approached the capabilities of home audio set-ups—Pioneer introduced the Supertuner with 1976’s KP-500 cassette player/FM tuner, boasting advanced circuitry, improved reception, and super-sensitive tuning capability. Cars began to feature multi-speaker stereo systems, with individual speakers outfitted on the driver side, passenger side, and rear deck, allowing for the sensation of surround sound. Most advancements in the car audio industry were now occurring in the aftermarket, rather than through stock systems.