IRT Cross
 
The IRT Cross is designed for ambiance pickup. The setup consists of four cardioid microphones.
The IRT cross is designed for capturing the ambient/diffuse part of a surround-sound recording. It is a four microphone square with 20–25 cm (7.9–9.8 in) between the cardioid microphones, which are routed to left, right, left surround and right surround in an appropriate level compared to a front array.
The IRT Cross is normally positioned a couple of meters behind the main array. However, it should not be placed too far away as there may occur timing problems (like an echo) in the reproduced signal. The optimal placing of the IRT Cross is a balance between getting enough ambiance while at the same time avoiding echo.
 

Object-Based audio
 
For years, the most enveloping loudspeaker-reproduced sound has been channel based. One channel is for mono, two channels are for stereo and six channels are for 5.1 surround-sound (or 24 channels for NHK 22.2).
Conventions regarding the placement of the loudspeakers for each format have been the backbone of the sound design. Inter-channel panning by the aid of delay- or level adjustments has been the tool for the placement of sources of the sound scene. The finished product would be contained in a fixed number of channels; even though the program material originally was recorded on a huge number of audio tracks, the final product would fit into a specific number of channels, one for mono, two for stereo, etc.  
The Object-Based Audio (OBA) is somewhat different. A "sound object" can be recorded on one or more tracks. Along with the audio goes the metadata that tells where to position the sound in the soundstage.
An object could be a voice recorded in mono. If the producers intend to let the voice come from the right of the soundstage, then the metadata of the voice recording contains the coordinates of this sound. The voice is for this reason recorded as a stereo track. Then the metadata of these stereo tracks provides the data for the positioning.
In principle, an object may also stem from an ambisonic recording or any other format. Therefore, an AV program with OBA is built up from a string of objects, like voice recordings, music, ambient sounds, special sound effects, etc. Each object will contain metadata on when and where to be reproduced.
OBA has already found its way to the cinema (Dolby Atmos and the like). However, it is the intention to bring it into broadcast as well, and many experiments have been carried out. In addition, virtual reality (VR) is an obvious target for OBA.
 

Why?
 
The general idea is to leave a higher degree of freedom to the listener, especially in broadcast. Now it is possible to emphasize a single object. If a hearing-impaired listener wants to level up the dialog, this is a possibility, if you record the dialog as an object. You can also change the language of the commentary, if you allocate each language to separate objects.
From TV productions like Formula 1 races, we know that special onboard cameras can be selected, if the viewer wants to follow a specific car. The sound of that specific car is an object in conjunction with the image. Specific musical instruments in an orchestra can be regarded as objects. Alternatively, the sound from a concert, recorded at different listening positions can be objects.
Another argument for OBA is that almost any reproduction format is valid. The downmix is optimized depending on the number of channels and their positions available for the playback (as long as the number of channels is at least two). Binaural reproduction is also allowed for.
 

Microphones?
 
The basic idea is that the sound engineer can use the kind of microphones that he likes. There is not necessarily a demand for specific microphones, microphone configurations or microphone brands. The special requirement goes on the production equipment, that can establish the metadata and of course to the formats that carry the complete information.
 

Suggested microphones & accessories
 
Omni-based surround array

• 4006C Omni Microphone, Compact
• 5006A Surround Kit of five matched 4006A microphones, clips and windscreens in Peli™ case
• S5 Surround/Decca Tree Mount

 
Cardioid-based surround array

• 4011A Cardioid Microphone
• 4011C Cardioid Microphone, Compact
• S5 Surround/Decca Tree Mount

 
Wide cardioid surround array (WCSA)

• 4015A Wide Cardioid Microphone
• 4015C Wide Cardioid Microphone, Compact
• 5015A Surround Kit of five matched 4015A microphones, clips and windscreens in Peli™ case
• 4006A Omni Microphone
• 4006C Omni Microphone, Compact
• 3506A Kit of two matched 4006A microphones, clips and windscreens in Peli™ case
• S5 Surround/Decca Tree Mount

 
Optimized cardioid triangle (OCT)

• 4011A Cardioid Microphone
• 4011C Cardioid Microphone, Compact
• 4018A Supercardioid Microphone
• S5 Surround/Decca Tree mount

 
Double MS
DPA does not provide any figure-of-eight microphones. We suggest the Schoeps MK8 with CMC6 preamp. However, if you want to try this setup with DPA microphones, we suggest you substitute each figure-of-eight microphone with two cardioid microphones:

• ST4011A Stereo Pair with 4011A Cardioids
• SB0400 Modular Stereo Boom
• UA0836 Stereo Boom

 
Fukada tree

• 4011A Cardioid Microphone
• 4011C Cardioid Microphone, Compact
• 4006A Omni Microphone
• 3506A Kit of two matched 4006A microphones, clips and windscreens in Peli™ case
• S5 Surround/Decca Tree Mount
• ST4011A Stereo Pair with 4011A Cardioids
• SB0400 Modular Stereo Boom

 
Hamasaki square
DPA does not provide any figure-of-eight microphones. We can suggest the Schoeps MK8 with CMC6 preamp. However, if you want to try this setup with DPA microphones, we suggest you substitute each figure-of-eight microphone with two cardioid microphones:

• ST4011A Stereo Pair with 4011A Cardioids
• S5 Surround/Decca Tree Mount

 
Immersive audio with height

• 8 x 4011A Cardioid Microphone
• 2 x 4018 Supercardioid Microphone

 
IRT Cross

• 4011A Cardioid Microphone
• 4011C Cardioid Microphone, Compact
• ST4011A Stereo Pair with 4011A Cardioids
• MMC4011 Cardioid Microphone Capsule
• MMP ER/ES Modular Active Cable
• SB0400 Modular Stereo Boom
• UA0837 Stereo Boom

 

DPA 5100 Surround Microphone

 The 5100 Mobile Surround Microphone is a plug-and-play solution.

One unit contains three directional (DIP-MIC, directional pressure microphones), coincidently arranged frontal microphones. The rear channels are recorded by a spaced pair of two omnidirectional microphones. The unit also provides an LFE-output. All channels are calibrated to unity gain. The LFE is reduced by 10 dB, according to the standard.

The 5100 is much appreciated in film production for 2nd unit work.


 

References
 
[1] Gasull Ruiz, Allejandro: A Description of an Object-Based Audio Workflow for Media Productions. Convention Paper 9570, AES 140th Convention, Paris 2016.
[2] Steven A.: Object-based audio for television production. IBC 2015.
[3] Messonnier, Jean-Christophe et al.: Object-based audio recording methods. Conference proceedings, AES 57th International Conference, USA, 2015.
[4] Shirley, Ben et al.: Personalized Object-Based Audio for Hearing Impaired TV Viewers. Journal of the Audio Engineering Society, Vol. 65, No. 4, April 2017.