| Notes | The Haeco-CSG or Holzer Audio Engineering-Compatible Stereo Generator system is an analog electronic device and method developed by Howard Holzer. His company, Holzer Audio Engineering, developed the system in the 1960s during the years of transition from monaural to stereophonic popular music recording. The process was used primarily from about 1968 until 1970 but still exists on a significant number of recordings made during the time.
Haeco-CSG technology works on the basis of phase cancellation. When two waves that are not in phase are mixed, the resulting waveform has an attenuation in accordance to the degree of shift. For example, two waves which are 180 degrees out of phase will entirely cancel out when mixed together whereas two waves which are entirely in phase will double in amplitude. A difference in phase between 180 and 0 degrees results in a partial cancellation, which is the effect Haeco-CSG takes advantage of.
The system electrically rotated the waveform of the right channel by up to 120 degrees to control the buildup of center information during a simple mono downmix. It is not known how exactly the circuit accomplished this; it did however do this without slightly delaying one channel. The most common listing of 90 degrees out of phase corresponds to Haeco's own recommended setting of the +3 dB build up, whereas no build-up would require a 120 degree offset. This setting was most commonly used because of its robustness against polarity reversal of audio interconnects down the chain, which can affect the resulting audio when downmixed to mono. Information that is not common to both channels is entirely unaffected as there is no offset phase wave to cancel with |
