The Technology of Fine Stereo: reporting an interview with Colin Attwell of Claudio Records Ltd, UK.
by Dave Billinge
http://www.claudiorecords.com/
Triggered by a very fine recording of Shostakovich's Piano Trio in E minor I travelled to Peacehaven in Sussex in March 2013 to talk to the engineer/owner of Claudio Records. On the cliffs above the town is his family home and company headquarters. Here we talked for nearly two hours about engineering stereo recordings. It was a rare opportunity to hear from the horse's mouth some of the technical issues of which we, as listeners, are ignorant. Colin has several decades experience within the industry, detailed on his website, making his comments doubly interesting.
Since the work of the recording engineer begins with his microphones, I started by asking Colin about his approach to microphone placement. He says he tries to find the 'ultimate spot'. The microphones (pro-AKG or pro-Neumann pairs rebuilt by himself to optimise sound) get the best seats, he said. He uses his ears to find the best place in the auditorium, but his ears are trained by 29 years of owning the same microphone pairs in the case of the Neumann’s, so he hears as his microphones hear. (This is technical, but in a nutshell a microphone responds to sounds differently to a human ear). Since he is not restricted by an auditorium seat this ultimate spot may be, indeed usually is, some height above any usual sitting position. When searching for this perfect place he will often have to resort to a stepladder. Height is beneficial because the clearest wave fronts from individual instruments, especially strings, are usually at an upward angle. He records pianos with their lids off particularly because that way he can treat them like a harp and place microphones where all strings are equally visible and fairly equidistant. This also makes for an even frequency response from the keyboard, a balance of bass and treble. In a sense he has to use his eyes as well as his ears to set up because the instrument's visibility is a good guide to its optimum audibility.
For reasons we will come to later, he uses only a single pair of microphones and this makes the positioning more difficult if all instruments are to be placed for the best sound. Because of this he will, in the recording sessions, move instrumentalists into places that suit his microphones and his ears rather than the other way round, at the same time optimizing the instruments for their ‘sweet spots’. For example, the piano trio in that Shostakovich recording was placed with the violin adjacent to, and to the left of the piano as seen from the keyboard, and the cello to the right. Both were facing away from the pianist at about a 45 degree angle (requiring the use of a mirror so that the pianist could be seen by the strings). The stand holding the microphone pair was placed at the foot of the piano with each microphone having one lobe of its figure-of-eight response towards each string player. The two microphones were thus at 90 degrees to each other and spaced 120mm apart, see below for an explanation of this distance. The rear response lobe of the microphones are aimed away from the musicians picking up the ambience of the recording space, here a church. Because the violinist and cellist would then be 'aiming' their sound boards beneath the microphone he had both players on tables to raise their aiming point to the height of the microphone. If one considers the trio's position relative to the microphone this required the channels to be reversed at the recorder to get the violin to sound from the left and the cello from the right. It sounds artificial as described and probably had its comic aspects for the musicians but the resultant stereo sound is quite remarkably pure and 'natural', an improvement on the audience's listening position, rather than something radically different. Recording live concerts, said Colin, is always a compromise because he can only place microphones at the best available position and cannot move musicians from standard concert layout, no tables when in front of an audience! Because of all this, the musicians have to trust the engineer to get it right. Colin trusts the musicians to perform at their best for his recordings and he in return expects them to trust him to capture their best sound and the best balance.
This trust is partially earned by trying not to stress his musicians overmuch, i.e. wasting time 'playing' with his setup. They want to play music, not watch an engineer climbing ladders and moving them around. To this end he keeps detailed notes of sessions for future reference. The notes are written and diagrammed pages showing exact equipment used, positioning and height of microphones, placing of musicians, including which way they are facing, and technical details of recording formats, type of microphone used and so on.
All of this requires careful preparation not only before each session but in the sense of being optimally equipped for any and all projects. Colin puts maximum energy into getting every recording as good as possible. To that end he spends around £2000 on each pair of microphones. He has two main pairs he has owned for well over a decade and relies on all the time. He has measured the distance between his own eardrums (120mm - presumably by calculation not major surgery!) and emulates this by setting his microphones at that distance on pre-drilled metal bars that are then mounted on the stands. Despite having bought expensive microphones from the likes of AKG or Neumann he still opens them up and removes filters, switches and anything else that degrades the quality of sound. He places his own-design microphone pre-amps (CMA-1XE http://www.claudiorecords.com/equipment.html) close to the microphones so that only amplified signals are sent down long cables to the recording devices. He never uses mixers.
He is scheduled to record two of the UK's major orchestras. In both cases they will be subjected to the same manipulation of position as the piano trio mentioned above. So the orchestra for a piano concerto will be placed almost in a circle around the piano and on tiered seating. This will allow line of sight from every musician to his single pair of microphones. He stresses that you cannot put a microphone in a convenient place and let the players get on and play. The process of recording for optimum 'natural' sound is of necessity artificial. Musicians, he believes, do not enjoy having multiple microphones close to them anyway, so his use of just two at a sensible distance goes down well with players. This is in marked contrast to the standard multi-microphone recordings of the big companies.
As an example of the traditional approach he describes the philosophy of one major player during the heyday of recording two or three decades ago. This classical recording company believed 'if it is in the score then you must hear it'. First they tried to get an acceptable sound in the recording venue using probably a main crossed pair plus up to 30 or 40 close microphones spread around the orchestra. They carried out a rough mix in the control room recording all microphone feeds at an optimal level for minimum distortion. In post production back at the studio the resultant tracks were then tweaked by ear to a level that allowed every note in the score to be heard but without losing a proper balance. This was an essentially musical aim but required a lot of microphones, good ears and good replay equipment at the mixing desk. The big problem with this whole approach is still that multiple microphones receive multiple wave fronts arriving at different moments and this makes for 'phase distortion', an artifact that the human ear can detect with ease and which damages the sense of reality.
In passing he notes that phase distortion is one of two reasons why he does not use surround recording: the extra microphones will add to phase problems. The other reason is that with the latest high quality stereo ‘matched’ microphones surround is not necessary in achieving a pure, natural almost three dimensional image! If the final mix is being made in the studio this means judgments are limited by the quality of replay equipment, most especially the monitor speakers. Colin uses a pair of vintage (1967) BBC LS5 1A monitors and Quad ESL 63s. He knows of one engineer who uses more recent Quad ESLs for this stage with wonderful results. For Colin it is important to know the monitors just as he knows the microphones, but regardless of this they have to be at an acceptable standard. He does question the replay standards adopted by critics - with good reason! If someone is going to publicly pronounce on the sound quality of an issue (and possibly affect sales) they should be able to point to their replay chain as being up to the required level. Some might do better, he thinks, to use good headphones where the quality can be achieved at lower cost.
He has nailed his colours to the mast for 24 bit word-length at a sampling rate of 192 kHz as the absolute standard and artists like the results. He is eager to do more big orchestra recordings to prove his point still more using a technique used in the days of Sir Thomas Beecham but with his special Q-LAB system, his name for the processes (or lack of processes!) he uses to keep the recording chain as pure and simple as possible. Tests carried out at the Wigmore Hall some time ago demonstrated to his satisfaction that, compared to a direct feed (from microphones to microphone-amps to power-amps to speakers), all recording machines inserted into the chain introduced audible losses until the machine worked at 24/192. Even the now-standard 24bit/96kHz, says Colin, is not quite good enough. CDs produced from 24/192 masters are better than those produced from lower resolution masters, despite having been downsampled for the CD format. The big problem is that because of lack of take-up there is little software capable of post-producing 24/192 sources onto DVD-A - which is also then limited to 66 minutes storage in stereo. Blu-ray, which can store large amounts of 24/192, is very expensive to produce and thus a problem for the budget. Despite all this he is convinced 24/192 is 'right' and he records everything at that rate. There is a growing American market for these DVD-As. He rejects SACD in passing because it can't store 24/192 and the SACD standard insists on imposing DSD coding which he says does not sound so good. It is also impossible to get the results manufactured in UK because no SACD processing plant exists within these shores. He believes that this insistence on 24/192 will eventually pay dividends and that HD is the future for real music lovers. He bemoans the fact that we now have the best processing available (24/192) but despite that the new 'standard' is 24/96 and not usually in simple stereo!
Colin agrees in a sense with the suggestion that recording techniques have not improved much since the 1960s and 70s. The technology of microphones and microphone amplifiers has of course improved but the way in which they are used has not. The use of larger numbers of microphones has made it easier to get the sound the engineer wants in the mixing room afterwards. For this reason he characterized it as a bit of a compromise system but with the benefits of post production correction for bad balances. The modern approach is always to use many microphones. He cites an example of an Eastern European recording project where the people he was working with on an orchestral recording actually preferred the sound he was getting with a single stereo pair but felt under pressure to use their standard multi-microphone approach because it was more modern and showed they had progressed. He feels that in a way he is going back to the early days of electrical recording when the musicians were crowded around the single microphone to make sure that microphone had the best possible sound from every instrument. The primary difference now is that with modern microphones a single pair will suffice to capture an entire chorus and orchestra within their natural acoustic if placed optimally.
He would have been happy to talk for much longer but my time had run out. I have to publicly thank him for his time and his frankness about his work. He sees himself as one of a fairly small group of professional enthusiasts for realistic recording. In an age of data-reduced MP3 downloads and multi-mike recording it is a brave and maybe uneconomic attitude. There are other paradigms followed by other engineers, but his seems well justified by his results. As evidence here are a handful of Colin's recordings, reviewed very briefly to give a flavour of his work as engineer.
Zoltan KODALY (1882-1967)
Sonata Op.8 for Cello Solo [30.19]
Henri DUTILLEUX (b.1916)
3 Strophes Sur Le Nom de Sacher for Cello Solo [9.34]
Benjamin BRITTEN (1911-1976)
Cello Suite No.1 Op.72 [20.37]
Oren Shevlin (cello)
rec. St Bartholomews Church, Brighton, England 2000
Claudio Records CD CC5046-2 [64.07]
This is a gem of a CD recorded in Colin's favoured acoustic, that of St Bartholomew's Church in Brighton. The programme is interesting of itself and the cellist is masterly. Oren Shevlin has been principal cello of the WDR Symphony Orchestra, Cologne for about 15 years and has a notable career as soloist with orchestras around Europe. He has not made life easy for himself by recording these three works, the Kodaly and Britten being amongst the peaks of 20th century cello repertoire. It is worth buying for the Kodaly alone, which is performed with a level of skill and insight that takes the breath away. The recording is quite beautiful and makes one wonder why anyone bothers with surround sound when plain stereo CD can sound this spacious without losing the tight focus of the cello at the centre of the stereo stage.
Maurice RAVEL (1875-1937)
Piano Trio
Dmitri SHOSTAKOVICH (1906-1975)
Piano Trio No.2 in E minor Op.67
Ibuki Trio, Ben Wragg (violin), Laura Anstee (cello), Kan Tomita (piano)
rec. St Bartholomews Church, Brighton, England 2008
Claudio Records DVD-Audio CR5890-6 High-Definition 24 bit 192 kHz Stereo, also available on CD CR5890-2
This was the recording that drew my attention to Colin's engineering skills. It is an object lesson in stereo sound recording of a small chamber group and described at length above. Fortunately the performances of both trios are excellent and worth owning for musical reasons as well. It could be argued that other recorded performances present the Shostakovich in a more powerful light but none, I am sure, sound so good as this. A CD is available but I only reviewed the high-definition DVD-A. For those who can play such discs, owners of universal players or Blu-ray players, it is a valuable addition to your music collection.
Michael MAIER (1569-1622)
The Fifty Fugues of Atalanta Fugiens [71.58]
Rachel Platt and Emily van Evera (sopranos), Rufus Müller (tenor), Richard Wistreich (bass and director)
rec. St Margarets Church Putney January 1986
Claudio Records DVD-Audio CR5468-6 High-Definition 24 bit 192 kHz Stereo (2 discs), also available on CD CR5468-2 (1 disc). The DVD-A data takes more space than can be stored on one DVD, the CD is complete on one disc. The original recording was on analogue tape.
I can only refer interested readers to the Wikipedia article on Michael Maier where he is described as " a German physician and counsellor to Rudolf II of Habsburg, a learned alchemist, epigramist and amateur composer." Atalanta Fugiens is described there as "an alchemical emblem book ... published in 1617; alongside images, poems, and discussion, it included fifty pieces of music in the form of fugues." Listening to this remarkable recording for any length of time induces a sort of hypnotic fascination. On the DVD-A one seems to be sharing the church with these three singers in a private performance. It is spectacularly realistic and musically intriguing. It also demonstrates how long Colin has been making these fine recordings since it dates back to pre-digital days when he recorded using analogue open-reel tape.
Frédéric CHOPIN (1810-1849)
Nocturnes Op.37, Op.48, Op.55, Op.62, Op.post.72, C sharp-minor Op.post.
Adolfo Barabino (piano)
rec. St Bartholomews Church, Brighton, England 2005
Claudio Records CD CR5570-2 [57.50]
Barabino is up against very serious competition with this CD because Chopin's Nocturnes are standard repertoire for all the great pianists. He certainly conjures up a dreamy world, with drama where required, and his recording is again very fine. This CD is Volume 2 of the Nocturnes, volume 1 also being available from Claudio Records on CR5569-2.