Kobak, the OQS Array

Live immersive audio recordings with a quadrophone microphone array

We have made live recordings at the XXII Hifi Show in Budapest in 2023 October. 6 Mini Concerts were recorded in stereo (on tape and in DSD256) and in 4 channel “quadraphonic” digital format as well as pure as the technology allowed it. The result is really immersive.

A unique microphone technology made it possible.

During the early ’80s, Jürg Jecklin published an engineering report in the Journal of the Audio Engineering Society. The article described a technique to use omnidirectional small diaphragm microphones in true stereo microphone array for two-channel recordings. The setup made it possible to utilise the benefits of omni microphones, bringing directionality to the array by a disk between the two microphones. The Jecklin disk was born, later renamed as OSS (Optimum Stereo Signal) setup

The OSS array proved its excellence. Since it became popular, some modifications emerged. The shape remained the same, but even Mr. Jecklin modified his original concept of enlarging disk diameter and microphone distance.

A new array was developed by Istvan Kishonti, a HUngarian sound engineer and scientist, while gaining experience using two OSS arrays separated by a third large disc for quadrophonic recording in the early 2000s. Thinking further came the idea of the new unified array.

It is called “the Kobak” (nickname of “head” in Hungarian) or OQS (Optimal Quadrophonic Signal). Kobak can be considered as four perpendicular jecklinlike plates melting into each other, dividing a sphere into four segments, each containing a flush-mounted microphone. The result is surprising. Using in stereo, there is a good separation from the front and rear half-space, giving a chance to optimize the balance of direct to reverberant sound despite the true omni directionality of the whole array. The stereo signal is perfect for both headphone and loudspeaker reproduction.

What about four-channel reproduction?

Why four instead of surround (5.1)?

Simply speaking, 5.1 is good for film but terrible for capturing the sound around us. First of all, in 5.1, the five channels are not equal. There is a misunderstanding even in quadrophonic reproduction considering directionality.

As there is no main direction for us in the real sound space, since we can turn around any time to observe sound sources in interest, the reproduced sound space should cope with it in theory. While in the real sound field, humans can localize sound from any direction with a certain precision without turning towards the source, this is not true in the reproduced four-channel sound field generated by four equal-quality channels. In the quadrophonic field, there are four equal directions that can always be perceived only with two speakers in front of the listener.

There is utmost importance understanding our inability to analyze virtual sound sources in the leftmost or rightmost directions while facing these said two front speakers. To perceive what is happening to the left or right, the listener should turn there to listen to two speakers with two ears again. This is the limitation of the quadrophonic reproduction, and the importance that the virtual sources are always shown via two speakers of all four directions gives the necessity to consider all directions equally.

In arrays with more than four channels, primarily for film and video, there is at least one dedicated channel for dialogue located obviously at a screen, designating the main direction.

The other serious problem with these arrays is that virtual sound sources can be reproduced perfectly only with two speakers or via headphones.

Every additional speaker further degrades the pin-point precision in localization. So, only the two or four-channel techniques can provide speaker pairs for good virtual reproduction.

Thus, the 4.0 to the 5.1 or higher surround arrays are different in setup, concept of usage, and reproduction. Kobak (or OQS) is designed to capture a real, immersive 360-degree sound space. As the predecessor Jecklin disk (OSS), it proved its excellence during the last 20 years.

The device is designed, by Istvan Kishonti of eurOpus Audio Ltd and used for hundreds of recordings since 2002.

Copyright by Koscso Media Engineering Kft/eurOpus Audio.

All rights reserved.