ORTF

ORTF
Name	ORTF
Type	microphonic array
Invented	1960s
Inventor	Service de la Recherche de la Télévision Française
Region	France
Typical angle	110°
Microphone spacing	17 cm
Microphone type	Cardioid pair

ORTF ORTF is a stereo microphone technique developed in the 1960s by French broadcasting engineers to capture realistic spatial cues using two cardioid microphones. It was created by engineers at a national broadcasting research group to balance interchannel time and level differences, yielding a natural stereo image suited to orchestral, vocal, and environmental recording. The configuration became influential across European broadcasting Radio France, BBC Radiophonic Workshop, Deutsche Welle, RAI, and independent studios, and remains a standard reference in microphone pedagogy alongside arrays such as XY stereo recording, Blumlein pair, and Mid-Side recording.

History

The ORTF technique emerged from postwar development in studio and field audio at institutions like Office de Radiodiffusion-Télévision Française research teams, paralleling innovations at NBC, CBS, BBC, and Deutsche Grammophon engineering labs. Engineers sought an intermediate solution between coincident arrays used by RCA engineers and spaced arrays employed by concert recording pioneers such as Arthur Nikisch-era practitioners and Alan Blumlein's stereo patents. Influences included directional microphone development at Neumann GmbH, studies at Institut National de l'Audiovisuel, and measurement programs used by broadcasters during events like the Expo 58 and broadcasts of the Festival d'Avignon. The configuration was standardized in French broadcasting practice and disseminated through technical papers, workshops at Radio France and conferences at AES.

Technical Setup

ORTF uses two cardioid microphones placed 17 centimetres apart with their axes angled outward at 110 degrees to approximate interaural time and level differences of human hearing. Typical microphone models used historically include the Neumann U87, Sennheiser MD 421, AKG C414, and designs derived from STC and Coles cardioids. The 17 cm spacing approximates the average human interaural distance measured in anthropometric studies similar to work at Institut Pasteur and university labs at Sorbonne University. The 110° angle is chosen to produce a 30–60° stereo sweet spot compatible with playback on systems such as BBC monitoring consoles, consumer equipment sold by Philips, Grundig, and broadcast mixers from Studer. Mounting hardware often employs shock mounts and boom arms from suppliers who served studios like Decca Studios and facilities used by Pierre Boulez and Herbert von Karajan.

ORTF balances time-of-arrival differences with level differences to reduce phase anomalies and to maintain monophonic compatibility for transmission chains used by RTÉ, NHK, CBC/Radio-Canada, and shortwave relays. Signal routing typically goes through preamplifiers by Neve, API, Studer, or Solid State Logic, then into multitrack recorders such as Ampex or digital recorders from Avid and Yamaha.

Usage in Broadcasting and Recording

ORTF is widely used for orchestral location recording, choral capture, acoustic guitar ensembles, film sound reference microphones, and field documentation for broadcasters like Arte, TF1, Canal+, and public radio services. Engineers at festivals—Salzburg Festival, BBC Proms, Glastonbury Festival, Montreux Jazz Festival—have deployed ORTF when a wide, natural stereo image is required without excessive room coloration found with large spaced pairs. Sound crews for directors such as François Truffaut, Jean-Luc Godard, Roman Polanski, and Louis Malle favored compact stereo rigs for scenes and location ambient tracks. In classical recording sessions at studios like Abbey Road Studios and Studio Ferber, ORTF has been used alongside techniques like the Decca tree for supplementary stereo perspective.

ORTF is also taught at institutions such as Berklee College of Music, Conservatoire de Paris, Royal Academy of Music, and technical schools affiliated with AES and RIAA certification programs.

Notable Recordings and Applications

Notable field and studio recordings employing ORTF or documented variations include broadcast concert captures by Radio France Philharmonic, live jazz recordings at Village Vanguard-linked broadcasts, and location sound for films by technicians who worked with companies like Gaumont and Pathé. Classical releases from labels such as Deutsche Grammophon, Harmonia Mundi, Erato Records, and Philips Classics used ORTF for chamber ensembles and small orchestras. High-profile festivals—Jazz à Vienne, Nice Jazz Festival, Sundance Film Festival—used ORTF in location capture for radio and television distribution. Field recordists documenting environments for projects like BBC Natural History Unit wildlife programs or ethnomusicology archives at Smithsonian Folklife have chosen ORTF for its balance of spatial realism and mono compatibility.

Criticisms and Limitations

Critiques of the ORTF technique center on its fixed geometry, which can be suboptimal in very large venues such as grand opera houses like Opéra Garnier or arenas used by touring acts like U2 and The Rolling Stones, where arrays such as the Decca tree or spaced omnis may better capture ambience. Purists advocating for coincident techniques such as Blumlein pair argue that ORTF can introduce comb-filtering when sources are close and off-axis, a concern raised in AES papers and by engineers from firms like Neve and Soundcraft. Broadcast engineers for networks like CNN, BBC World News, and Al Jazeera sometimes avoid ORTF when strict mono-sum phase linearity is required for transmission. Additionally, microphone choice, preamp coloration, and improper placement can degrade intended spatial cues, leading technicians at studios like Sun Studio and Musikverein to prefer alternative arrays.

Category:Microphone techniques