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Article from 31. May 2022
Source: https://www.avguide.ch/blog/puristische-oss-technik-als-audiophiles-ideal-aufnahmen-im-klangschloss
Purist OSS technology as the audiophile ideal
2-channel stereophony became the standard for music recording after its
introduction 70 years ago and has remained so. Since then, there has been eager
debate about which is the optimal method for immortalising music on two
channels.
In the "Klangschloss", three bands are recorded directly onto a tape machine using only two microphones and the famous "Jecklin disc". The tape is the basis for a "straight2tape" double LP. This ultrapuristic process offers the best conditions for authentically capturing magical moments of music-making.
Living Stereo - Cult recordings from the stereophonic founding era
Many classical music lovers will be familiar with the "Living Stereo" LPs from the "golden era" of sound recordings: RCA Victor launched the new stereophonic technology with this brand in 1954. A great deal of importance was attached to excellent quality, which was to radiate throughout the entire RCA group. Therefore, the stars of the classical music scene of the time, such as violin virtuoso Jasha Heifetz, pianists Arthur Rubinstein and Vladimir Horowitz, conductor Fritz Reiner with the Chicago Symphony Orchestra, were hired at great expense.
In a longer interview from 1996, the producer at the time, Jack Pfeiffer, also mentions the deliberate simplicity of the sound technology. A few microphones placed precisely in the hall were to capture the sound body as genuinely as possible. Each microphone would catch every sound in the hall; too many microphones would only cause phase errors and a terrible mess. You would no longer know what you were doing. There was a lot of experimentation until the mid-1960s, but the
principle of simplicity was maintained. Usually 4-5 microphones were used, 3 of them for the front channels plus support microphones.
Other companies took similar approaches. Decca created the "Decca Tree" and called the recordings ffss (full frequency stereophonic sound), Mercury's series was called "Living Presence". To this day, the recordings from this period are considered the "gold standard". Original pressings fetch top prices at collectors' markets. Those interested can find a lot of documentation on the internet. The techniques were rarely used for pop and jazz as well. The recording of Harry Belafonte at Carnegie Hall, for example, has become famous.
Essential for a successful recording according to this pattern: excellent acoustics and musicians who are well versed in their pieces. Post-production is virtually non-existent. The recordings are live takes. It was customary to record the pieces in one take. With the advent of larger mixing consoles and multitracking, this rigid pattern was gradually abandoned in the mid-60s.
More and more microphones were used and the sound was created at the mixing desk in the sound control room. The resulting much greater recording freedom was immediately exploited in popular music. In serious music, which knows the ideal of the concert experience in real spaces, it took longer. But large orchestras can also be recorded more flexibly in this way and the sound can be artificially shaped. Because there is an ideal, attempts have been made until today to orient multi-track recordings according to it - with often dubious results.
OSS technology (Optimum Stereo Signal)
At the beginning of the 1980s, Jürg Jecklin, sound engineer at Radio Studio Basel for many years, conceived the OSS technique as an alternative to multitrack technology and wanted to initiate a discussion about sensible recording methods. His approach: If the sound is already optimally present in a concert hall, why not capture it optimally right away?
Two microphones for two stereo channels would have to suffice. However, the usual methods for such purposes were not sufficient for him. The so-called small A/B technique delivered a naturally balanced sound, but a poor quality of imaging. With the ORTF technique, it was just the opposite.
ORTF microphone arrangement (cardioid characteristic)
The solution was a disc the size of an LP, which he damped acoustically on both sides. To the side of it he mounted two condenser microphones with omnidirectional characteristics, which are ideal in terms of sound. He directed the microphones away from the disc at an angle of 30° each, so that
the membranes were 32 cm apart. This produced a vividly precise image. The idea fell on fertile ground, but not so much with professional sound engineers as with amateur sound engineers.
While the professionals were deprived of their complex means and at best used the disc as their main microphone, the hobbyists suddenly had a tool in their hands with which they could achieve good results without much prior knowledge and with little effort. "A disc recording hardly ever sounds bad," Jecklin said. But for it to sound really good, a number of prerequisites are necessary.
As with the "living stereo" recordings, these include good hall acoustics, as well as an optimal position of the disc and the musicians in the room. Patience on the part of those involved in finding the positions is therefore required. And finally, the following applies to the recording: One Take!
Jecklin disc during test recordings in the Landenberghaus
Jecklin had many stories to tell about the disc. For example, that of a sound engineer colleague who confided in him that he would always record with the disc parallel to his recordings. This served him as a check on the quality of his work. On Jecklin's hint that he could make the recording with the disc at the same time, his colleague thought about it for a moment. The idea was not wrong. But he stuck to his method.
Live Recording Sessions with the Jecklin Disc
When we stood in the new concert hall of the Landenberghaus for the first time on the open day and listened to the string sounds of the responsible acoustician Eckhard Kahle, we knew that this hall was a gift for the Klangschloss. Kahle walked through the hall quietly playing his viola and explained the acoustic concept in between. Kahle Acoustics is one of the most renowned acoustics specialists in the world and has such well-known references as the new Philharmonie in Paris. https://kahle.be/de/referenzen.html
