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Phaedrus Audio Shuphler

Stereo-correction Matrix
Published July 2017
By Hugh Robjohns

Phaedrus Audio Shuphler

Most people, engineers included, have probably never heard true stereo imaging over speakers — now’s their chance...

We’ve already reviewed two Phaedrus processors — the Hydra mic preamp (SOS March 2016) and the Phamulus vari-mu compressor (SOS July 2016), both of which have unique qualities. But the subject of this review — and apologies in advance to any typographers reading this — the Shuphler Stereo Matrix, is more unusual still. Also part of the London Series, this device offers a unique set of stereo image processing tools designed to correct inherent weaknesses in a variety of conventional stereo systems and mic techniques.

Two Confusing

When discussing stereo imaging manipulation, a frequently encountered term is ‘shuffling’. Somewhat confusingly, it actually has two different meanings...

The term was first coined by Alan Blumlein in the 1930s, during his pioneering work at EMI developing stereo sound systems and techniques. In short, his Shuffler was conceived to process the outputs from a closely spaced pair of omni mics, converting low-frequency phase differences between the two channels into the amplitude differences necessary for the accurate recreation of stereo images from a pair of spaced loudspeakers — a scheme described in detail in Blumlein’s original 1931 patent. Unfortunately, Blumlein’s near-spaced omni mic technique (which we’d now think of as a binaural technique) has rarely been employed in the recording industry, and so his innovative Shuffler processing was largely forgotten, too.

The second ‘shuffling’ process was devised in the 1950s by members of the same EMI engineering team who’d worked with Blumlein before the war. It was an entirely different processing scheme (though it used similar core technology) designed to correct and improve the imaging of all stereo loudspeaker reproduction systems. EMI incorporated this ‘Stereosonic Shuffler’ into several of their in-house REDD mixing consoles, and it was routinely employed on EMI’s classical recordings in the ’50s and ’60s — but it too was later abandoned and has largely been forgotten.

So, there are really two fundamental forms of shuffler: the Blumlein Shuffler, and the Stereosonic Shuffler, and that’s how I’ll refer to them throughout this review. Both are catered for in the Shuphler, along with three other related processes.


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Published July 2017