Surround Sound Recording

5-1-surround-sound

“5.1 Surround Sound” by Kamina (Wikimedia Commons)


Early Experiments

I have been interested in Surround Sound for a long time. While I was still an undergraduate I assisted Granville Cooper and and Sid O’Connell in experiments that were presented at the London Audio Fair in the Hotel Russell. The BBC were also at that time presenting to a very small section of the public late night/early morning experimental broadcasts in surround sound that utilized two stereo radio receivers tuned to different stations. These took a lot of setting up, but I recall hearing enough interesting and convincing effects on these broadcasts to stimulate further experimentation. As a founder member of the English branch of the AES, I came into contact with Michael Gerzon, who was then developing Ambisonics and took part in several sessions evaluating recordings that they made to test the system – in all three planes.

During my time as a recording engineer at Abbey Road Studios, I persuaded my bosses to let me do some experimental recordings in Surround Sound, using a four-channel Studer J-37 tape machine. The first of these was done at King’s College, Cambridge, where Neville Boyling and I were recording Christmas Carols. Using a figure of eight pair of KM56 microphones for the back channels, and the regular stereo pickup for the front channels, I played this back to the Director of the King’s College Chapel Choir, David Willcocks. Hearing a take immediately after conducting the choir in the chapel, he declared that it “felt like being there”. Of course, like many musicians who were among the first to hear the improvements that have been made in the craft of sound recording over the years, he was unknowingly exaggerating; but what he heard was definitely an improvement on stereo.

Two other recordings followed – one in Abbey Road’s No.1 Studio and the other at Guildford Cathedral – but they were not as successful. I concluded that the King’s recording had worked largely because of the large amount of reverberation in the building, which gave a good wash of surround sound, but little directional information, which caused me to place the rear-channel microphones relatively close to the singers. This meant that there was an acceptable delay between the front and rear channels, and the latter, being a Blumlein stereo pair, preserved a good image of the choir. The walls of Guildford Cathedral, on the other hand, had been treated by the original builders with a material that greatly reduced the reverberation. I was unable to monitor this recording in surround on the spot, and because of the larger size of the ensemble used a pair of U87 microphones in omnidirectional pattern for the rear channels. In order to get any effect of distance, I had to move the microphones so far back that the delay involved was too great. This was a useful lesson, but of course, I only discovered it back at the studios, when it was too late!

The recording done in No.1 Studio Abbey Road was of a band of Gurkha soldiers playing bagpipes while marching back and forth. In order to protect the microphones and keep them out of the way of the heavy boots, I installed them in the catwalk above the studio. These microphones were four STC hypercardioids mounted on a wooden frame and as close to each other as I could get them in an attempt to simulate a Soundfield Microphone. Walk-about experiments indicated that, when played back over four loudspeakers, this array did indeed enable a listener to locate and follow the direction of a moving source of sound. The problem was that the bagpipes were so loud, and the sound source was so large because they were all playing the same tune. This caused the sound to bounce randomly between all the walls, with the result that it was impossible to tell where the players were, except in a general sense.

It was after this that EMI and other record companies launched Quadraphonic Sound, which utilized four loudspeakers, but which was doomed to failure by an over-optimistic system of matrixing four channel into the two channels of a vinyl disc. This was played back by a conventional stereo pickup and processed. In the best case, this gave some effect of sound at the rear, but there was little true directional information. The crosstalk of the system was just too great.

I did some recordings at the University of Surrey and Indiana University that employed the Calrec Soundfield Microphone. Early models of this microphone were difficult to use, as many examples needed careful adjustment of levels in order to avoid excessive noise or distortion. In those days, Nimbus Records invested heavily in ambisonic recording, but its commercial releases on vinyl were encoded in UHJ, a 2½ channel compromise, and did not issue their products on discrete-channel media until recently.


The present Day

Surround Set-up

A Typical Loudspeaker Layout for 5.1 Surround

With the advent of digital video recordings and home theatre systems, surround sound became a reality for the consumer, and the establishment of SACD and DVD-A allowed six discrete channels for audio-only recordings in the 5.1 format. Current technology goes further, by enabling streaming in surround sound and the download of high resolution surround recordings as multichannel FLAC files. In 2006, encouraged by the ability to cut my own DVD-A multichannel discs and having heard some good commercial examples, I again embarked on my own experimental Surround recording. The technical bais of these experiments and the microphone I have designed are detailed here.


Commercial Realities

Following the appearance of the first stereo LPs in 1958, the adoption of stereo continued to be very slow throughout the 1960s, and the same has proven true of surround sound. One of the early complaints about stereo was the need to have two loudspeakers, and this argument has been compounded with the necessity of at least four for surround. Surround sound has caught on in the form of home movie theatre, and the irony of movies in surround is that in almost all of them the dialogue comes entirely from the center front channel. It was to solve this problem that Alan Blumlein lavished a lot of ingenuity in his invention of stereo some 80 years ago!

As of the end of 2018, dedicated audio reproduction systems on the market are still predominantly confined to stereo – both for physical media and for replay from computer files. I have been particularly surprised that audio journalism has not lead the way in embracing surround sound. The premier audio magazine, Stereophile, is still heavily focussed on two-channel stereo. In October 2001 (Vol.24, No.10) a letter of mine to this magazine was published advocating greater coverage of Surround Sound. It responds to an article by Sam Tellig that had appeared in the August issue, and demonstrates the serious regard in which I hold music recordings and the development of technology that has made real surround sound possible.

Editor: It seems that there are some who believe that Stereophile's name is a barrier to its promotion of multichannel surround sound. I would remind them that stereo does not mean “two channels only,” but is derived from a Greek word meaning “solid.” I interpret this as multidimensional.

It is ludicrous to maintain that surround sound will become a reality only if the big companies push it. This may have been true 30 years ago, when quadraphonic sound was being pushed by the recording companies (EMI, CBS, RCA, etc.), which controlled not only the recorded repertoire and the artists allowed to become famous, but also the pressing facilities and the recording technology. But today all that has changed, and many classical musicians who had been made famous by these same companies are now without recording contracts. At the same time, thanks to digital technology and the Internet, control of the production and distribution of quality recordings is no longer in the hands of the few.

In his June As We See It, Kalman Rubinson wrote that when he plays multichannel recordings at home he is “inhibited from doing anything but paying attention to the music.” I fail to see the problem here. Is music made for listening to, or for ignoring? Composers, performers, engineers, and producers spend a lot of time taking care over details in recordings and controlling quality so that something enshrined in a piece of plastic can give the impression of live music and communicate with us; and this gentleman now complains that they have done their jobs too well!

What has become of the slogan “the closest approach to the original sound”? If Peter Walker and others had not had that ever in mind, it is doubtful whether we would have progressed beyond mono LPs. In this context, stereo as we know it is but a staging post on the trail; yet I have in front of me a letter, published in April 1950 in the British magazine Wireless World, in which the chief engineer of the BBC assured readers that the BBC had no plans to “radiate binaural transmissions“ – ie, stereo. His argument was quite succinct, and was along the lines of there being no public demand for it. Like stereo radio, sooner or later multichannel surround sound will become the norm – and I hope that Stereophile will be up there with the real leaders.

David Pickett Letter from Wireless World, 1950

I must admit that I know very few people that have invested in surround playback in their homes, and it is disappointing that all the recordings that I have made to date have been distributed in stereo only. The expense of four decent loudspeakers and room to accomodate them are undeniable problems, but I hope that a growing interest in realistic sound reproduction – Peter Walker’s “closest approach to the original sound” – will eventually overcome these.

Technical information about Ambisonic Recording may be found here.

Rev. 8 Dec 2018