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All information in these pages is copyright (c) 1989-2003 by Roger Nichols. All rights reserved. Permission for personal reference only, and may not be reproduced by any method without written permission.
I Can’t Keep Up With All The Formats
Part 1 of 3
by Roger Nichols
Back in the “Good Old Days” there was one final mix format: mono.
Actually, there was no mix… even the recordings were in mono. How easy
could it get! Records had evolved from the cylinder to the 78, and then finally
the 45 and 33 1/3 rpm LP, but they were all monaural. It took over 20 years
from the time they started messing around with stereo recordings until there
was actually a stereo product for the consumer.
One of the earliest stereo recordings was done in 1932 in Philadelphia for
Bell Labs. The recording by Stokowski of Scriabin’s “Poem of Fire.”
It was done on a vinyl disc using two grooves, one for each channel. Two years
later stereo recordings were being done at Abbey Road studios using a vertical-lateral
technique. Decca records released the first stereo records in 1945 using the
vertical-lateral system. They could not be played well by the current playback
systems. “The Robe”, in 1953 was the first movie to be released
in Cinemascope with a stereo (actually 4 channel) soundtrack. There were more
than 30 other stereo films released that year.
1954 was a good year for stereo recordings. RCA made the first commercially
available recordings with a RCA RT-11 two-channel recorder and a pair of Neuman
U-47 microphones. RCA actually released open reel tapes of stereo recordings.
These tapes sold for about four times the price of an LP. EMI was recording
“stereosonic” recordings at Abbey Road, and Decca was using the
first Ampex 350-2 15ips, two-track recorder for its stereo recordings.
LP format wars raged until 1958 when the RIAA adopted the Westrex 45/45 system
as the standard for stereo records. The 45/45 system was actually patented
by Arthur Keller for Bell Labs in 1932. The application not actually filed
until 1936 because Bell saw no useful
purpose for the invention. I wonder what else he didn’t patent?
The 45/45 system is a technique where each wall of the record groove moved
independently of the other. The left channel modulated one wall and the
right
channel modulated the other wall. If the material recorded was mono, the
groove moved laterally. If the material was completely out of phase,
the groove moved
vertically. Mono phonographs only recognized lateral movements of the stylus,
which would only play back the in-phase portion of the recorded material.
Talk about format wars, FM stereo was having a battle of its own. There were
two competing formats, the Crosby system, which used an FM sub-carrier for
higher fidelity, and the Zenith/GE system that used an AM modulation system
for the sub-carrier. In 1961 the FCC chose the Zenith/GE system as the standard.
That is why FM stereo is noisier than FM mono. The signal that gives you the
stereo is AM. I had a Fisher FM tuner in the late ‘50s that had a Crosby
and Zenith decoder. Stations in LA used to do test broadcasts of both systems.
I remember how much better the Crosby system sounded. Oh, well.
The matrix system used in FM worked this way: The left and right channels
were split into two stereo streams. In one stream the right and left channels
were added together to form a mono signal. In the other stream the right
channel was phase inverted and subtracted from the leftt channel resulting
in a difference
signal. The main carrier of the FM station broadcast the mono signal. All
mono FM receivers could demodulate this signal. The difference signal
was
broadcast on the sub-carrier frequency that could be decoded by a stereo
FM receiver. For the left channel the difference signal was added to the
mono
signal. For the right channel the difference signal was subtracted from the
mono signal. In the Zenith/GE system the AM difference channel is where
the
noise comes from.
Also around 1961 a dual optical system was developed that allowed two-channel
sound for film. Yes, the films started driving the marked for multi-channel
(only two for now) audio in the home.
Mono Compatibility
Early stereo recordings were exaggerated in their stereo placement. Most consoles
did not have pan pots yet, so the program material was assigned to the left
channel or the right channel. When the two signals were combined for mono
radio broadcast, the results were pretty good. As production techniques added
panning to the bag of tricks, stereo started calming down and most stereo
program material tried to realistically represent the left/ right spread of
a true listening environment. When you added the two channels together for
mono, information that was placed in the center (phantom) of the mix got louder
than material that was placed on one side or the other. Engineers were very
careful with phase relationships in stereo recordings because out of phase
portions of the recording would cancel completely when combined to mono. In
the early days of stereo records and stereo radio broadcasts, very few people
had the new-fangled stereo gear to playback this high-tech source material,
so stereo records and stereo FM broadcasts had to be compatible with existing
mono playback equipment.
Mono Mixes
Because of the way the left and right channels add together when combining,
the balance of the stereo mix is changed when listening in mono. All of the
material panned to the center in a stereo mix, (lead vocal, kick drum, bass
and snare drum) will be louder when listening in mono, while instruments panned
far left and far right will be very low. This is not good if you are trying
to promote your record from airplay on radio station that is being heard in
mono.
When a group was in the studio mixing their album the record company required
mono only mixes to be done at the same time the stereo mixes were done for
the album. The artist punched the MONO button on the console and made the
balance changes necessary to make the mix sound good in mono. Bring down the
stuff in the middle, and ride up things that were panned way out to the sides.
Sometimes you had to change the reverb and other effects because of the mono
combination. The mono version was used to press the 45rpm singles and promotional
copies that were sent to the AM radio stations. FM radio usually played the
album version of the song, which was in stereo.
Some groups (Steely Dan comes to mind) refused to do mono mixes of their albums.
They mixed their masters in stereo and whatever happened at the radio station
was up to fate. Sometimes the engineer would hit the mono button on the console
to check for bad stereo-to-mono artifacts, but only for 30 seconds one time
during the entire album mix process (who, me?).
Quad, Surround of The ‘70s
And then in the ‘70s came Quad. There were basically two commercial quad
formats competing for the market share (I won’t even mention quad 8-track
tapes). One was the JVC CD-4 system that worked a lot like FM transmission
(45kHz recorded on a vinyl record). The main stereo channels were in their
normal groove configuration so as to be stereo compatible. The back channel
difference information was added into a 30kHz sub-carrier that could be removed
by a quad decoder. The second system was the Sansui QS system (based on the
CBS SQ system from 1969) that used phase encoding to get the rear channel
information in and out of the stereo mix.
Because of the phase encoding system, there would be some strange artifacts
when listening to a stereo record on a quad system or a quad record on a stereo
system. Separation from front to rear channels was bad in the phase-encoded
systems and the calibration and noises from the JVC system were horrible.
Consumers did not get the whiz-bang they expected, and producers were lax
at making surround mixes of their album projects. We did mix one Steely Dan
release in Sansui Quad that won a Sansui “Best Quad Mix of The Year”
award. Other than that, quad made a sad attempt at a format and died a slow
death by the end of the ‘70s.
Stay Tuned
In the next two installments I will cover cassette, 8-track, EL-cassette,
PCM-F1, DAT, DBX, CD, MP-3, DSD, DTS, AC-3, MLP, MPEG-2, DVD, DV, DV-PRO,
DVD-A, Digital Radio, and anything else I can dig up.