List of Ambisonic Hardware

Main article: Ambisonics

This is a list of current or legacy Ambisonic hardware.

Currently available Ambisonic Hardware

Microphone Arrays

Presence in this list does not indicate that the manufacturer uses the term Ambisonics for marketing or even endorses the concept at all, merely that the product produces B-format or something closely related.

Domestic surround processors/amplifiers

Legacy hardware

A popular and unfortunate misconception is that Ambisonic recordings can only be made with the SFM, and as a result there is a widespread, and erroneous, belief that Ambisonics can only be used to capture a live acoustic event (something that accounts for a tiny proportion of modern commercial recordings, the vast majority of which are built up in the studio and mixed from multitrack). This is not the case. In fact, Michael Gerzon's designs for Ambisonic panpots pre-date much of his work on soundfield microphone technology. Ambisonic panpots – which allow mono (for example) signals to be localised in B-Format space – were developed as early as the 1970s, and were incorporated into a special mixing console designed by Chris Daubney[1] at the IBA (UK Independent Broadcasting Authority) and built by Alice Stancoil Ltd in the early 1980s for the IBA surround-sound test broadcasts.

Ambisonic panpots, with differing degrees of sophistication, provide the fundamental additional studio tool required to create an Ambisonic mix, by making it possible to localise individual, conventionally recorded multi-track or multi-mic sources around a 360° stage analogous to the way conventional stereo panpots localise sounds across a front stage. However, unlike stereo panpots, which traditionally vary only the level between two channels, Ambisonic panning provides additional cues which eliminate conventional localisation accuracy problems. This is especially pertinent to surround, where our ability to localise level-only panned sources is severely limited to the sides and rear.

By the early 1980s, studio hardware existed for the creation of multitrack-sourced, Ambisonically mixed content, including the ability to incorporate SFM-derived sources (for example for room ambience) into a multichannel mix.[2] This was thanks primarily to the efforts of Dr Geoffrey Barton (now of Trifield Productions) and the pro-audio manufacturers Audio & Design Recording, UK (now Audio & Design Reading Ltd). Barton designed a suite of outboard rack-mounted studio units that became known as the Ambisonic Mastering System.[3] These units were patched into a conventional mixing console and allowed conventional multitrack recordings to be mixed Ambisonically. The system consisted of four units:

It is understood that versions of these units were subsequently made available in the late 1990s by Cepiar Ltd along with some other Ambisonics hardware. It is not known if they are still currently available.

A significant number of releases were made with this equipment, all in 2-channel UHJ, including several albums on the KPM production music library label, and commercial releases such as Steve Hackett's Till We Have Faces, The Alan Parsons Project's Stereotomy, Paul McCartney's Liverpool Oratorio, Frank Perry's Zodiac, a series of albums on the Collins Classics label, and others, most of which are available on CD. See The Ambisonic Discography in the List of Ambisonic Productions for more information. Engineer John Timperley employed a transcoder on virtually all his mixes over the course of over a dozen years until his death in 2006. Unfortunately the albums, film soundtracks and other projects he created in UHJ over this period are largely undocumented at present, and thus remain unlisted in the Discography.

The custom preamp designed by Dr Jonathan Halliday at Nimbus, and an UHJ encoder.

The lack of availability of 4-track mastering equipment led to a tendency (now regretted by some of the people involved) to mix directly to 2-channel UHJ rather than recording B-format and then converting it to UHJ for release. The fact that you could mix direct to 2-channel UHJ with nothing more than the transcoder made this even more tempting. As a result, there is a lack of legacy Ambisonically mixed B-format recordings that could be released today in more advanced formats (such as G-Format). However, the remastering – and in some cases release – of original 2-channel UHJ recordings in G-Format has proved to be surprisingly effective, yielding results at least as good as the original studio playbacks, thanks primarily to the significantly higher quality of current decoding systems (such as file-based software decoders [4]) compared to those available when the recordings were made.

Spreaders

Other tools included "spreaders" which were designed to "de-localise" a signal (typically by varying the virtual source angle with frequency within a determined range) – for example, in the case of reverb returns – however these were not developed further.

Domestic Ambisonic decoders/amplifiers

Super stereo

A feature of domestic Ambisonic decoders has been the inclusion of a super stereo feature. This allows conventional stereo signals to be "wrapped around" the listener, using some of the capabilities of the decoder. A control is provided that allows the width to be varied between mono-like and full surround. This provides a useful capability for a listener to get more from their existing stereo collection.

A different kind of "super stereo" is experienced by listeners to a 2-channel UHJ signal who are not using a decoder. Because of the inter-channel phase relationships inherent in the encoding scheme, the listener experiences stereo that is often significantly wider than the loudspeakers. It is also often more stable and offers superior imaging.

Both features were used as selling points in the early days of Ambisonics, and especially Ambisonic mixing. It helped to overcome a "chicken and egg" situation where record companies were reluctant to release Ambisonic recordings because there were few decoders in the marketplace, while hi-fi manufacturers were unwilling to licence and incorporate Ambisonic decoders in their equipment because there was not very much mainstream released content. On the one hand, it was worth having a decoder because you could get more out of your existing record collection; while on the other it was worth making Ambisonic recordings because even people without a decoder could gain appreciable benefits.

References

  1. ↑ Chris Daubney, Ambisonics – an operational insight. Studio Sound, Aug. 1982, pp.52–58
  2. ↑ Richard Elen, Ambisonic mixing – an introduction, Studio Sound, September 1983
  3. ↑ Michael A Gerzon and Geoffrey J Barton, Ambisonic Surround-Sound Mixing for Multitrack Studios, AES Preprint C1009, 2nd International Conference: The Art and Technology of Recording May 1984. http://www.aes.org/e-lib/browse.cfm?elib=11654
  4. ↑ AES paper 7977; http://www.aes.org/e-lib/browse.cfm?elib=15274


This article is issued from Wikipedia - version of the 5/11/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.