Recently we at HHB had the pleasure of being a part of was the Exploring the Cinematic Hemisphere for Orchestra (ECHO) Project. ECHO was a collaboration of Audio Professionals and Academics, spearheaded by Professor Hyunkook Lee, Dr. Katia Sochaczewska, and Nick Wollage the aim of the project was to experiment with the use of different microphone array configurations for capturing cinematic orchestral pieces in immersive formats. The centrepiece of this project was a day long recording session at AIR Studio’s Lyndhurst Hall where an original piece by composer Volker Bertelmann, conducted by Hugh Brunt, and played by the London Contemporary Orchestra was recorded testing eight different proposed microphone array focus groups.
The recording session ended up utilising in excess of 100 microphones simultaneously. HHB, along with Avid and other sponsors, had been tasked with designing and providing a system and solution that would make such a session possible.
The main factors we had to consider were the high input channel counts and the need for flexible outputs. The plan was to construct a temporary 7.1.4 monitoring room in one of the booths on one side of the control room as well as a room that had options for binaural fold down monitoring on the other side but at the same time being able to provide a suitable amount of analogue output channels to feed through the desk in the control room for monitoring, all of these feeds needed to be monitored simultaneously.
Another consideration which we had to bear in mind during the system design and specifying stage of the project, was the importance of consistency and transparency of the microphone preamps. This was due in part to the analytical requirements of the academic research aspects of the project.
With the scope and requirements of the session established, we quickly decided that the onboard Dante I/O and MADI I/O with optional Thunderbolt I/O that are available on an Avid MTRX II along with the quality, constancy and transparency of the analogue option cards made it the perfect solution for such a session.
The resulting system of that was decided upon consisted of two Avid MTRX IIs populated with
- 14 Avid Mic/ Line Cards to provide up 112 channels of analogue input.
- 2 Avid 8 Channel Analog Output Cards
- A Thunderbolt I/O option module in each MTRX II
Along with the MTRX IIs, we used an Avid MTRX Studio which provided the additional 16 analogue output channels.
A diagram of the routing between the selected I/O units
The signal flow was designed with redundancy and flexibility in mind. The 106 microphone feeds came into the A/D cards split across the two MTRX IIs. The MTRX II which was receiving 64 Channels (Unit 2 in the Diagram), had all the microphone feeds patched into the master MTRX II via MADI. This was in order that the main Pro Tools recording rig was able to receive all the channels from both units via a single Thunderbolt connection.
The microphone feeds that were input directly to the master MTRX II were simultaneously patched to the second MTRX II via a Dante network, this allowed us to attach a backup Pro Tools recording rig to the second unit via its Thunderbolt card. The Dante network was in place as a backbone of routing to for the session, this was used to feed the Binaural room with the channels it required, as well as feeding channels to the MTRX Studio to output to the control room desk and monitoring system via its analogue outputs.
The 7.1.4 Monitoring room took its feed via the DigiLink ports on the Master MTRX II. This was a third Pro Tools system, this time using two HDX cards to take all the microphone feeds from the Master MTRX II and input them into a Pro Tools session. The operator of this rig would group the microphones in the different arrays, and then switch between the arrays to output to the speakers, allowing us to get a good idea of how the different immersive microphone arrays would sound in real time. This was mapped out and panned using the Internal Pro Tools Dolby Atmos renderer.
The range of features and flexibility of the Avid products we used in this project were integral to its success. From the ability to deal with high channel counts with very low latency, huge amounts of simultaneous signal conversion formats, to the brilliantly well thought out monitoring and SPQ functionality of the units. This was a project which should have pushed any I/O to its limits. The Avid products we selected and used for this project took it all it their stride, instilled confidence in the session organisers and engineers, and helped make the project a success.
