The Hafler circuit is a passive electronics circuit with the aim of getting derived surround sound or ambiophony from regular stereo recordings without using costly electronics. Such circuits are generally known as matrix decoders. The Dynaquad system works using similar principles.[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.[2] This type of system is called 2:2:4, since the rear channels are simulated from a two-channel stereo track, with no actual extra tracks encoded. The rear channels will playback out of phase sounds, while the forward channels are unaffected. 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).
- ^ Berry, Ray (February 1975). "Four Channel Sound". The Michigan Technic. 93 (4). University of Michigan, College of Engineering: 6–10.
- ^ Elliott, Rod (1999). "Simple Surround Sound Decoder". Elliott Sound Products. Archived from the original on 28 November 2016. Retrieved 13 December 2016.