ORTF-Miking Technique

The ORTF (Office de Radiodiffusion Télévision Française) miking technique is a stereo microphone technique commonly used in audio recording, particularly for capturing stereo soundscapes such as orchestras, choirs, and live performances. Developed by the French broadcasting authority in the 1960s, the ORTF technique aims to create a natural and realistic stereo image by mimicking the spacing and angle of human ears.

Here's how the ORTF miking technique is typically set up:

1. Microphone Placement:
   - Two cardioid microphones are spaced apart and angled outward at a specific angle to replicate the stereo width of human ears. The distance between the microphones and the angle of the microphones are crucial for achieving accurate stereo imaging and sound localization.
   - The microphones are positioned at an angle of 110 degrees between them, with their capsules spaced apart by 17 centimeters (approximately 7 inches). This spacing and angle closely resemble the distance and angle between human ears, providing a natural stereo perspective.

2. Height and Distance:
   - The microphones are typically positioned at a height corresponding to the height of the sound source or ensemble being recorded. For example, in orchestral recording, the microphones may be placed at a height of approximately 1 to 2 meters above the conductor's head.
   - The distance between the microphones and the sound source depends on the desired balance between direct sound and ambient or reverberant sound. Closer microphone placement emphasizes the direct sound, while farther placement captures more of the room ambience.

3. Stereo Image:
   - The ORTF miking technique creates a natural stereo image with a spacious and immersive soundstage. The spaced cardioid microphones capture the subtle time and level differences between the sound arriving at each microphone, resulting in a sense of depth and localization in the stereo field.
   - The 110-degree angle between the microphones provides a wide stereo spread while maintaining phase coherence and minimizing phase cancellation, ensuring a coherent and stable stereo image across the frequency spectrum.

4. Phase Coherence:
   - Phase coherence is important in stereo recording to ensure that the signals from the two microphones sum coherently when mixed together. The ORTF technique's specific spacing and angle help maintain phase coherence between the microphones, resulting in a balanced and natural-sounding stereo image without phase cancellation or comb filtering effects.

Overall, the ORTF miking technique is a versatile and effective method for capturing stereo recordings with a natural and immersive soundstage. It is widely used in audio recording applications where accurate stereo imaging and spatial realism are desired, including classical music recording, field recording, and live sound reinforcement.