Microphones X-Techniques have been developed by Riccardo Mazza, Chief Engineer and Partner of Renaissance Sound Technologies, specifically for the production of the Renaissance Dolby Surround Encoded Library.

The research has been addressed in order to achieve a “surround” tridimensional recording encoded on just 2 tracks and the possibility to decode the result back on 4 channels using a standard Prologic decoder. In this way users are able to record on location with a normal 2 track DAT recorder on the field and then rebuild the original spatialization during the post-pro sessions.

If correctly balanced, X-Techniques do not need to be Dolby surround encoded, thus completely preserving bandwidth and dynamic of original recordings. Besides LCRS encoding, this application is very useful for 5.1 productions as well and since the encoded tracks are stereo compatible, it becomes a very practical task to monitor and distribute such material using for example a standard audio CD.

X-Techniques have been created in order to obtain the most effective motion along the speakers: specific techniques have been developed for different kinds of situation like natural environments, motions, city trax etc. The development of these techniques has been mainly addressed to the entertainment industry and it’s not intended for medical or scientific purposes.

So we have:

- some techniques that enhance certain kinds of motions (like a car “pass by” in a city track);
- others that surround the listener (like in a rain storm);
- some others that really separate the dominance of the sources in the dimensional space (like in a natural jungle environment where you may hear maybe a bird on the back, an insect on the left etc.).

All these recording techniques use many of the psychoacoustic laws to get maximum audience impact.

In order to use X-Techniques you will need some dedicated tools that have been created along with the techniques themselves. The main encoding process is made throught the X-Mat.

X-Mat is a matrixed circuit that allows a maximum of 5 microphones inputs and 2 channel encoded outputs called Lx and Ly.
X-Mat consists either in an hardware portable mixer and a DSP based plug-in.

The both cases final results are the same. The hardware gear provides 5 high quality mic pre-amps at the input stage, in spite of the plug-in that needs external mic pre-amps.

The matrix is a double 5 input with links on ch 1-2 and 3-4, phase switch on each channel. Each of these channels is independently addressable to one or more of the 4 busses. Each bus can reverse the phase once again and it is addressable at output Lx and/or Ly.

Each stage of the circuit must be phase-correlated and each summing stage (links, busses, assign, Lx and Ly) must be trimmed at nominal level otherwise all coding will not work properly (that’s why the software version have to be DSP based).

The DSP based plug-in has been realized using Creamware Scope programming environment connected to a Digidesign system via ADAT bridge. The Prologic decoding has been used with the Dolby Surround TDM plug-in and all testing as the post pro has been done in the TDM environment as well.

Each of the following X-Techniques needs the relative X-Mat mapping.

Many other techniques are under development at now; the following are the ones that have been successfully employed during the production of the Renaissance SFX library.