The story
The invisible centre speaker.
Ordinary stereo creates its centre image as a phantom between two loudspeakers. Sit exactly where the system expects and the illusion can be convincing. Move sideways and the image begins to pull towards the nearer speaker. That was an awkward weakness for cinemas, presentation spaces and domestic rooms where people rarely sit in one mathematically perfect chair.
Michael Gerzon had developed the underlying Trifield theory for deriving a more stable three-speaker presentation from stereo. AGM turned that theory into professional hardware: the TSS-1 and the programmable TSS-1D. The latter added centre-channel delay, RS-232 control and PC software so an installation could be adjusted and then left to run.
A Verdi Requiem finds a centre channel
One of the nicest surviving examples is not a demonstration disc but a real remastering job. For a Pioneer Classics DVD of Verdi’s Requiem, mastering engineer Steve Hall worked from the stereo recording made at Frankfurt’s Alte Oper and passed it through an AGM TSS-1 to create the left-centre-right foundation for a 5.1 version. The box was being used for exactly the sort of practical translation problem it had been designed to solve.
And then it simply stayed in service
A contemporary review reported TSS units already installed in roughly twenty German fixed installations, many associated with video presentation. Much later, in 2022, two AGM TSS-1 processors appeared in an auction of equipment recently decommissioned from the Royal Opera House, Covent Garden. For specialist audio hardware, quietly remaining useful for that long may be the best product review of all.