Despite being discussed since the earliest days of stereophony, there remains much confusion about the term Stereo Shuffling. This is not surprising because the term actually refers to two, quite separate and different techniques.
1. Simply put, the earliest use of the term (coined by no less than Alan Blumlein himself1), refers to the processing of near-spaced omni' microphone signals so that they reproduce correctly on loudspeakers.
2. The second Shuffler was invented some twenty years later for the processing standard stereo signals to give better realism.
Why use the same name? Well the later "Shuffler" was invented by the EMI team who had worked with Alan Blumlein before he was killed in WW2. Perhaps they sought to honour him in adopting the term which derived from him?
In any case, the Pspatial Audio's Stereo Lab incorporates both type of historical Shuffler.
We prefer not to refer to the first Shuffler (due to Blumlein) as a Shuffler. Instead we call this the Blumlein Delta algorithm. Michael Gerzon said of this that it was, "the greatest forgotten invention in audio engineering." and we agree! Effectively a binaural to summation-stereo transcoder, this technique is explained here.
The later Shuffler (due to the EMI team who developed Blumlein's ideas into a commercial product after his death) is implemented in the FRANCINSTIEN algorithm. FRANCINSTIEN implements the EMI Shuffler without any of the unfortunate artefacts which plagued the original 1950's circuit. The more recent Bride of FRANCINSTIEN is a refinement of the FRANCINSTIEN and gives even better results on jazz, pop, rock and electronic music. Finally, there is FRANCINSTIEN T-Sym, a brand-new, phase-linear, digital shuffling algorithm which is impossible to do in the analogue domain.
1 Go to the British Library's website to hear Alan Blumlein speaking about Shuffling. For a short biography of Alan Blumlein, go here.
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Apple Certified Developer. Stereo Lab, Aria 51, Aria 20, Head Space, Groove Sleuth, iLOOP and FRANCINSTIEN T-Sym are trademarks of Pspatial Audio. FRANCINSTIEN and Bride of FRANCINSTIEN (BoF) are trademarks of Phaedrus Audio. Macintosh and the Mac logo are trademarks of Apple Computer, Inc.