Bluetooth Classic is the name given to the Bluetooth specification we're all familiar with from headsets and speakers. In 2010 the Bluetooth SIG (the promoters of Bluetooth) introduced a new specification referred to as Low Energy (or BLE). To differentiate the two, they adopted the Classic moniker. Bluetooth Classic is a short range wireless protocol that enables connecting devices like smartphones and speakers or hands free systems.
Although Bluetooth Classic and BLE share many components, they are not compatible. Rather, they work side by side. A Bluetooth Classic radio can't connect to a Bluetooth LE radio.
The range for Bluetooth Classic is typically around 10-20m. When Bluetooth Classic uses high data rates for quality audio the range drops because the high data rate requires a high signal level.
Audio quality depends on the CODEC used. The standard SBC Codec is typically poor, but using codecs like AAC, MP3, and proprietary ones will improve the audio quality significantly. The new LC3 codec introduced in Bluetooth 5.2 is also available for Bluetooth Classic and provides good audio quality at reduced data rates.
Bluetooth Classic is still the best technology to stream high quality audio because it's widely supported. Although the Bluetooth 5.2 specification introduced LE Audio it's not widely supported.