Stereo over the air

Early Bluetooth audio was aimed at voice calls. The Bluetooth Special Interest Group says the Advanced Audio Distribution Profile, or A2DP, was adopted with supporting specifications in 2006 to make stereo music streaming possible.

A2DP describes how a source such as a phone sends audio to a receiver such as headphones or a speaker. The music is encoded for transmission and decoded for playback; the wireless link is not a direct copy of the electrical signal from a headphone socket.

From accessory to expectation

Wireless headphones existed before the fully separate earbud became familiar. Apple introduced AirPods in September 2016 and announced availability that December; their charging case and automatic setup showed how much of the experience now depended on connection design as well as sound.

A wireless speaker similarly separated the music source from the place where sound came out. The phone could remain in a pocket while the speaker filled a room.

A new audio architecture

Bluetooth SIG announced LE Audio in January 2020. Its specifications were completed in July 2022; the LC3 codec specification had been released in September 2020. LE Audio uses Bluetooth Low Energy and supports features such as coordinated streams and broadcast audio.

Classic Audio and LE Audio are different technical paths. Both are part of wireless listening, and neither changes the basic need for a source, a radio link and a device that turns data back into sound.

Names that mattered

Listed because of what they did, not as recommendations. Velorex Music did not make any of these.

Did you know?

• Bluetooth SIG dates the adoption of A2DP and its supporting specifications to 2006.
• The LC3 codec specification was released in September 2020.
• The full LE Audio specification set was completed in July 2022.