The please-readme-file SOS MMAD 0.4 SOS_MMAD.htm

The SOS_MMAD Website project will cover most aspects of Multichannel Microphone Array Design, including eventually arrays for two, three, four, five, six, seven and eight channels. These arrays are or will be designed initially for microphones with 1st order directivity patterns (Hypercardioid, Supercardioid, Cardioid, Hypocardioid and Omnidirectional).

Arrays will also be shown for Surround and Front Sound Stage Coverage with links to "ROOT ARRAYS", "NATURAL ARRAYS" and "STEERED ARRAYS".

"STEERED ARRAYS" includes designs needing Microphone Position Offset and probably Electronic Time Offset to obtain Critical Linking. This categorie was formally called "ALL ARRAYS"

"NATURAL ARRAYS" do not need any electronic offset to obtain Critical Linking, Critical Linking is achieved by Microphone Position Offset only i.e. simply by the position and the orientation of the microphones.

"ROOT ARRAYS" are a special case of "Natural Arrays" where the angle between the microphones is the same as the Segment Coverage angle and no Segment Steering by Electronic Offset or Microphone Position Position Offset is necessary to achieve Critical Linking. This can help considerably in visualising the segment coverage angles the limits of which are aligned with each microphone direction.

I'm afraid that no links are available for the time being to any Natural Arrays, and Root Arrays are only available for 4 and 5 Channel Front Sound Stage Coverage (FSSC) Arrays.

Since publication of the previous releases of the SOS_MMAD CDROM, the MMAD diagrams have been redrawn in high definition PDF format, and extended to cover:
- Surround Sound Coverage for 5 Channel Microphones Arrays in Supercardioid, Cardioid and Hypocardioid directivities.
- Front Sound Stage Coverage (FSSC) for 3, 4 and 5 Channel Microphone Arrays using Omnidirectional, Hypocardioid, Cardioid and Supercardioid directivities.

'Help' files have been included on the Backtracks and Crosstracks table and can be consulted using the symbol ' ? ' to the link.

The microphone coordinates and orientations, that have been used for most of the diagrams, are contained in papers presented at various AES Conventions :

Preprint 5336 « The Quick Reference Guide to Multichannel Microphone Arrays Part 1 : using Cardioid Microphones » by Michael Williams and Guillaume Le Dû, presented at the 110th AES Convention in Amsterdam in 2001.

Preprint 6059 « The Quick Reference Guide to Multichannel Microphone Arrays Part 2 : using Hypocardioid and Supercardioid Microphones » by Michael Williams and Guillaume Le Dû, presented at the 110th AES Convention in Amsterdam in 2001.

Preprint 6230 « Multichannel Sound Recording using 3, 4 and 5 channel arrays for Front Sound Stage Coverage » by Michael Williams, presented at the 117th AES Convention in San Francisco in 2004

The present SOS_MMAD Web-site project contains over 11500 Multichannel Microphone Array Designs with different 1st order microphone directivities, and uses HTML driven access covering a range of specific selection criteria as explained in the paper presented at the 24th AES International Conference :

« Multichannel Sound Recording Practice using Microphones Arrays »
by Michael Williams

There are still many links / pages / chapters to be completed - be patient!

The measuring of the anglular coverage segments is always a problem. A prototype design of a measuring instrument called 'The Crocodile' was described in the publication 'St Zoom'. A more streamlined version is shown in 'Microphone Support Systems and Accessories' and can be purchased from Michael Williams at mail@soundscot.com (price 240€).

Operation of the Web-Ste
The recommended screen resolution is 1024 x 768, with the browser viewing on "Full Screen".

For direct access to the Home Page MMAD you should run "SOS_MMAD.htm" or you can access the next page via the "SOS_MMAD" link at the top or bottom of this page

From the "SOS_MMAD.htm" page you can access the wide range of Multichannel Microphone Arrays Designs via the "Microphone Array Design" link and then select the links to either 4 or 5 Channel Microphone Arrays. Surround Sound Arrays are only available in 5 Channel Array designs, however Front Sound Stage Coverage (FSSC) arrays are available in both 4 and 5 Channel configurations. After choosing the Microphone Array Design link on the SOS_MMAD page, there are another 6 stages in choosing the final array design :

FIRST : Choose the required number of channels and either 'Surround' for 360° coverage or 'FSSC' for Front Sound Stage Coverage only.

SECOND : Choose the microphone directivity (Omnidirectional, Hypocardioîd, Cardioîd, Hypercardioîd, Supercardioîd or Bidirectional) and the type of array ('STEERED ARRAYS'- 'NATURAL ARRAYS'- 'ROOT ARRAYS' )

THREE : Choose the Front Triplet Coverage values for 5 Channel Arrays or the Front Coverage for 4 Channel Arrays - select either the numerical configuration value or the image plan icon.

FOUR : Select the required microphone configuration from the various configurations that will produce the Front Triplet Coverage or Front Coverage selected previously.

FIVE : Select the Lateral Segment and Back Pair Coverage value according to the estimated response of the acoustical environment generating the group of early reflections and the general reverberation.

SIX : Select the desired microphone configuration from the various possibilities that are shown and will produce these Lateral Segment and Back Pair Coverage values. This will lead you to the last page, which is a detailed plan of the chosen array in PDF format. This can be printed out preferably in "landscape" format on any printer. A colour printer is an advantage to reproduce the colour coding in the diferent segments. However the colour luminosity values have been chosen so as to be compatible with a b/w printout.

It is essential to experiment different segment coverage values until you find the optimum array design or your particular preference. If you have difficulty determining the physical representation of the various segment angles with respect to the actual sound stage, you should build the "Crocodile" optical measurement tool described in either of the books by Michael Williams - "The Stereophonic Zoom" or "Microphone Arrays for Stereo and Multichannel Sound Recording" or purchase the streamled version now avalable from mike@soundsscot.com

Please note that a Positive Electronic Offset value shown on the microhone array plan requires delay of the specified value to be applied to the Front Triplet set of microphones with respect to the Back Pair of microphones. Negative delay values on the other hand mean that the Back Pair of microphones is delayed by the specified value with respect to the Front Triplet set of microphones. Detailed analysis of the Offset Segment Steering process is contained in AES preprint 4997. This Electronic Offset can be easily introduced on a Computer based recording system such as Pro Tools simply by shifting the respective tracks by the specified offset value (calculated either in the number of samples or directly in mS).

5 Channels Surround Arrays which do not need any form of Electronic Offset have not yet been shown specifically on this release. This information will be found in the tables shown in AES Preprint 5336 « The Quick Reference Guide to Multichannel Microphone Arrays Part 1 : using Cardioid Microphones » by Michael Williams and Guillaume Le Dû

For the time being, this is not a stand alone product, it must be read in conjunction with the previously published AES papers (as shown in the list below). Many of the terms used have been explained in detail in these papers. Terms such as Front Triplet Coverage, Lateral Segment Coverage, Back Pair Coverage, Microphone Position Offset, Electronic Time Offset etc. must be well understood to be able to use the data correctly.

The theorectical background to the two channel microphone array (stereo) and the development to the MMAD process has been presented at various in papers published at Audio Engineering Society Conventions over the past few years :

STEREO
1984 : 75th AES Convention in paris - Preprint 2072

«The Stereophonic Zoom - A Practical Approach to Determining the Characteristics of a Spaced Pair of Microphones» by Michael Williams

1987 : 82nd AES Convention in London - Preprint 2466
« Unified Theory of Microphone Systems for Stereophonic Sound Recording » by Michael Williams

1990 - 88th A.E.S. Convention in Montreux - Preprint 2931
« Operational Limits of the Variable M/S Stereophonic Microphone System » by Michael Williams

1991 : 91st AES Convention in New York - Preprint 3155
« Early Reflections and Reverberant Field Distribution in Dual Microphone Stereophonic Sound Recording Systems » by Michael Williams

1992 : 92nd A.E.S. Convention in Vienna - Preprint 3252
« Frequency Dependent Hybrid Arrays for Stereophonic Sound Recording »
by Michael Williams

1992 : 93rd A.E.S. Convention in San Francisco - Preprint 3413
« The Basic Principles of I.S.S.R. (Individual Sound Source Reinforcement »

by Michael Williams

MULTICHANNEL
1991 - 91st AES Convention in New York, Preprint 3157  
« Microphone Arrays for Natural Multiphony » by Michael Williams

1999 : 107th AES Convention in New York : Preprint 4997
« Microphone Array Analysis for Multichannel Sound Recording » by Michael Williams and Guillaume Le Dû

2000 : 108th AES Convention in Paris : Preprint 5157 :
« Multichannel Microphone Array Design » by Michael Williams and Guillaume Le Dû

2001 : 110th AES Convention in Amsterdam : Preprint 5336
« The Quick Reference Guide to Multichannel Microphone Arrays Part 1 : using Cardioid Microphones » by Michael Williams and Guillaume Le Dû

2002 : 112th AES Convention in Münich : Preprint 5567
« Multichannel Microphone Array Design : Segment Coverage Analysis above and below the Horizontal Reference Plane » by Michael Williams  

2003 : 24th International AES Conference
« Multichannel Sound Recording Practice using Microphones Arrays » and a presentation in a poster session of a new concept for a « Multichannel Microphone Support System » by Michael Williams

2004 : 116th AES Convention in Berlin : Preprint 6059
«The Quick Reference Guide to Multichannel Microphone Arrays - Part II : using Supercardioid and Hypocardioid Microphones »
by Michael Williams and Guillaume Le Dû

2004 : 117th AES Convention in San Francisco : Preprint 6230
«Multichannel Sound Recording using 3,4 and 5 channel arrays for Front Sound Stage Coverage » by Michael Williams

2005 : 118th AES Convention in Barcelona: Preprint 6373
«The Whys and Wherefores of Acoustic Cross-talk in Multichannel Microphone Array Design » by Michael Williams

2007 : 122nd AES Convention in Vienna - Preprint 7057
«Magic Arrays – Multichannel Microphone Array Design Applied to Microphone Arrays Generating Interformat Compatability» by Michael Williams

2008 : 124th AES Convention in Amsterdam - Preprint 7480
«Migration of 5.0 Multichannel Microphone Array Design to Higher Order MMAD (6.0, 7.0 & 8.0) with or without the Inter-format Compatibility Criteria»
by Michael Williams

These papers and other AES documents can be ordered from aeseuroservices@aes.org or from www.aes.org

The author has also published : "Stereophonic Zoom" in English and "Le Couple Variable" in French which explain in detail the theory behind the design of a stereo array, and also gives some guidance for experimentation in recording of different sound sources.

MICROPHONE ARRAYS FOR STEREO AND MULTICHANNEL SOUND RECORDING Vol 1 by Michael Williams was been published by "Il Rostro" in MILAN in 2004. It is planned to publish the second volume sometime in 2008. Volume 1 covers - the loudspeaker configuration and the listening room - the training of the ear - the operational approach to stereo and multichannel sound recording - a tutorial on microphones. This book costs 20€ plus postage and can be purchased from Michael Williams at mail@soundsscot.com.

The second volume of this book will probably include the SOS_MMAD CDROM with various Powerpoint and HTML based programs to aid in the teaching of the theory behind the process of microphone array design, together with both teacher's story-board notes and student back-up documentation.

The "Crosstrack/Backtrack shortcut" system has been entirely restructured, to allow greater flexibility and better legibility. Backtracking and Crosstracking to any previous stage in the design process is now possible. I hope all links are operational - please excuse me if this is not the case, there are now over 80000 links within the whole MMAD process and this is becoming difficult to completely check!

If you wish to receive a pre-release of the SOS_MMAD and of course future updates, please send your name, address, telephone & fax number and email to mail@soundsscot.com and I will put you on the mailing list. A nominal charge of 5€ will be made to cover the costs of postage.

I would be interested in hearing about your experience of sound recording using any of the microphone arrays described - please send any remarks to Mike Williams at mail@soundsscot.com.

Here is the link to the next page - "SOS_MMAD.htm"

Mike Williams
3 March 2009
mail@soundsscot.com