Many thanks indeed Geoffrey for that clarification.
Alan
-----Original Message-----
From: Geoffrey Barton
Sent: Tuesday, January 10, 2017 11:45 AM
To: sursound@music.vt.edu
Subject: Re: [Sursound] The BBC & Quadrophony in 1973
Message: 10
Date: Tue, 10 Jan 2017 08:42:43 -0000
From: "Alan Varty" <alan.va...@talktalk.net>
To: "Surround Sound discussion group" <sursound@music.vt.edu>
Subject: Re: [Sursound] The BBC & Quadrophony in 1973
Message-ID: <26495940C1B04DA6B9C600AD83F69931@AlanPC>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=response
I think I am correct in saying the BBC (H) and NRDC (45j) decided to
co-operate rather than have yet another two competing systems on
the 4-channel scene which at the time already had CD-4, UD-4, SQ and
QS in the arena. BBC/NRDC each modified their encoding "towards"
each other and called it HJ.
As I recall, the BBC were getting bad reviews of the stereo produced by
matrix H and discussed this with MAG who proposed a compromise. UHJ was a
variation within the 5 parameters which define an Ambisonic encoding, mainly
a reduction in the centre front phase shift compared with 45J, based on many
listening tests. It was known internally as 35JA’, so you can guess there
was a whole family of small variations. BBC HJ was defined as a set of
tolerance zones on the locus, mainly defined with reference to pairwise
panning, I think it coincided with the UHJ locus at four points , so in that
sense it was compatible; the exact parameters of both variations were
defined by MAG. In subsequent tests the BBC made, primarily using SFMs, they
also used our encoders, so I suspect drama productions such as Gilgamesh and
Inferno Revisited are actually UHJ.
Geoffrey
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