On Tue, 9 Jan 2001, Kieran wrote: > Has anyone ever produced any double vinyls of the same track with a1 being a > particular track and c1 being the same track, but with the inverted phase > wave? When both a1 and c1 are perfectly mixed, the inverted and normal waves > should totally cancel each other out, and there should be (in theory) complete > silence. Yet, as soon as they are pitch shifted/slightly out of phase, then > the tune(s) should jump in. > You could try it, but I doubt that you could keep it near enough in sync to really cancel, and most of the time it would sound flanged, similar to how rocking regular doubles sound.
The flanging of regular doubles comes from frequency dependent phase cancellation. You can phase cancel pure sine waves by offsetting one signal exactly one cycle. But a complex signal -- like a Jeff Mills track -- is continuously changing, and slight offsets mean some frequencies cancel, and some frequencies reinforce, so you get a comb filter effect. What's REALLY interesting to a record geek like me is taking two different records that are similar enough to phase cancel. Chic's 'GoodTimes' and Sugarhill Gang's 'Rapper's Delight' are like this -- RD recreated the Good Times loop so precisely that when you line it up it flanges with the original.
