Hafler circuit

[1] Named after its early proponent audio engineer David Hafler, the circuit exploits the high amount of stereo separation between Left and Right channels and sound phase.

Using the circuit typically reduces stereo separation by only about 2 dB and the rear speakers are only required to reproduce a limited frequency range (allowing them to be smaller and cheaper).

This can be most easily achieved by wiring two similar additional rear speakers in series between the live feeds (positive terminals) from the stereo amplifier.

[citation needed] The Hafler circuit is capable of partially decoding a Dolby Surround track since both share the same operating principles (based on sound phase differences).

Tandy Corporation used this circuitry for Quatravox matrix decoders used in their Realistic branded Hi-Fi systems sold at their Radio Shack stores in the US.