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BBC Proms

Rigging For Radio & TV
By Hugh Robjohns

BBC Proms in London's Royal Albert Hall.BBC Proms in London's Royal Albert Hall. All 76 concerts are broadcast live in stereo on BBC Radio 3, and this year an experimental 4.0 surround version is also being streamed from a dedicated web site. In addition, 27 of the concerts are televised on BBC One, BBC Two or BBC Four, some live and some as delayed or recorded concerts, but all in HD with a live 5.1 surround-sound mix.

Broadcasting every single Promenade Concert is a huge challenge for the BBC’s sound teams — especially as radio and TV have completely different requirements!

This year is the 120th anniversary of the BBC Proms. The annual classical music festival runs from mid-July to mid-September, and is hosted by the Royal Albert Hall (RAH) in London. Every one of the 76 concerts is broadcast live in stereo on BBC Radio 3, and this year an experimental 4.0 surround version is also being streamed from a dedicated web site (http://rdmedia.bbc.co.uk/proms/). In addition, 27 of the concerts are televised on BBC One, BBC Two or BBC Four, some live and some as delayed or recorded concerts, but all in HD with a live 5.1 surround-sound mix.

Sir Henry Wood’s concept for the Proms concerts was to present the widest possible range of music, performed to the highest standards, to large audiences, and that remains the case today (see the ‘Promenade History’ box). The typically eclectic programme of this year’s festival included familiar works from the likes of Bach, Beethoven, Berlioz, Chopin, Duruflé, Dvor k, Elgar, Mozart, Mussorgsky, Rachmaninov, Saint-Sa ns, Tavener, Tchaikovsky and many more. Several concerts featured alternative musical forms including Eastern music, jazz and electro-acoustic music, and there were also special children’s shows and 11 special Late Night Proms. One of the latter premiered a new work by the Pet Shop Boys, inspired by the mathematician Alan Turing, while others featured Laura Mvula and Paloma Faith. Most of the Proms concerts are performed by the BBC’s own orchestras and choirs, but many are given by invited world-class orchestras, choirs, soloists and conductors.

Overview

The scale of what is involved in the sound coverage of the Proms will surprise many, and I was delighted to be invited by BBC Radio Outside Broadcasts Senior Sound Supervisor Simon Tindall to see how things are done. I duly found myself at Door Eleven of the Royal Albert Hall in the week leading up to the First Night concert. The majority of the microphone and equipment rigging takes place in this week, and everything has to be in place and working by Thursday afternoon, ready for the first rehearsal of the opening concert. However, the stage area isn’t accessible on Monday as the lighting grid is being constructed and doesn’t go up until Tuesday — so the Wednesday I was there was pretty busy!

A small fleet of Outside Broadcast (OB) trucks are the most visible aspect of the broadcasting operation, parked for the entire duration outside the South-West quadrant of the hall in a fenced-off area called the ‘BBC Compound’. A previous year’s setup can be seen on Google Earth’s street view! One of these vast trucks provides a high-quality mixing room for the BBC Radio 3 sound balancers, while another plays the same role for the television surround mix. Both contain Stagetec digital consoles: an Aurus in the BBC’s Sound 3 vehicle for Radio 3, and a Cantus in the Sound Alliance TV truck. The monitoring in the Sound Alliance truck is a full Dolby 5.1-specification Bowers & Wilkins 800-series system, while the Radio 3 truck has huge MusikElectronic Gethain RL901k three-way coaxial monitors, with a pair of small Dynaudio monitors for auditioning the rear channels of a surround mix. There is no centre speaker or subwoofer for an LFE channel, as the surround mix is pure 4.0.

A third, and even larger, truck from NEP Visions provides the main television production control room, with associated vision and sound mixing facilities. All of the camera, sound, data and power cabling to and from these trucks disappears down a purpose-built manhole in the road, and reappears in a room under Door 11 for onward connection to all the camera, sound and control points around the hall.

Sound & Vision

In a former life, nearly 30 years ago, I worked on the Proms as a lowly sound assistant with BBC Television OBs, but things have evolved considerably since then — for all of us! In those days the television output was mono and derived from passive splits of the microphones rigged by the BBC Radio team. Today, although most of the microphone feeds are still split and shared, it’s all digital over MADI, and TV’s requirement for a full 5.1 surround output necessitates a completely separate set of microphone arrays.

Simon Hancock checks one of the suspended KM140 choir mics.Simon Hancock checks one of the suspended KM140 choir mics.

I use the plural ‘arrays’ here because different concerts involve very different repertoire and differently sized orchestras and ensembles, ranging from huge symphony orchestras with massed choirs down to chamber orchestras, small groups, and even individual soloists. Since the majority of mics are ‘flown’ above the stage and can’t easily be adjusted during the tight turnarounds between concerts, a considerable number of different mic arrays are required to ensure something is always available in a suitable place. The result is over a dozen catenary wire slings stretching across the width of the hall, spanning from just in front of the organ right back almost to the rear of the arena area. Each sling carries multiple microphones intended to serve very specific purposes, and although not all are used at once — of course — they are all used at some point during the eight-week season.

On the BBC Radio 3 side of things, this year 16 London-based senior balancers (Studio Managers or SMs in Beeb-speak) share the mixing duties between them, along with three senior audio staff from the BBC Regions who mix the BBC National Orchestra of Wales, BBC Scottish Symphony Orchestra and BBC Philharmonic, respectively. A small team of junior audio staff are always on hand to assist in various capacities as well, of course. Naturally, different SMs have different specialisations, usually acquired because they made a good job of something and got allocated to that genre again! For example, four Radio 3 studio managers tend to do most of the BBC Symphony Orchestra work, among them Simon Hancock who was also supervising the flying rig installation and explained the setup to me. One of his colleagues, Michael Bacon, tends to look after the organ works, Paul Waton does the musicals, and Marvin Ware the amplified electronic concerts involved in the Late Night and special Proms.

This view of the stage shows the Radio Spaced Pair and Radio Tree arrays behind and above the TV Decca Tree, plus some of the Radio Curtain and conductor pair mics.This view of the stage shows the Radio Spaced Pair and Radio Tree arrays behind and above the TV Decca Tree, plus some of the Radio Curtain and conductor pair mics.The working roster for a Prom concert typically means arriving at the RAH for 1pm to rig any required stage mics and to check everything is working correctly before the start of rehearsals at 2.30pm (although some orchestras prefer to rehearse in the morning and rest in the afternoon). A default setup is stored in the Radio 3 Aurus sound console to provide a pretty reasonable starting point (see ‘Mixing The Proms’ box), into which the additional stage mics are incorporated and the mix built from there. Afternoon rehearsals are scheduled to finish around 5.30pm, allowing time for any adjustments and a meal break before the 7.30pm live broadcast which finishes around 10pm. However, sometimes the rehearsals will last only 30-45 minutes, in which case previous experience comes in very handy indeed!

The 11 Late Night Proms are, in some cases, logistically much more complex, as they tend to involve heavily amplified multi-mic setups. These are rehearsed in the morning, with the crew arriving at 7.30am to start rigging. After the rehearsal finishes at lunchtime (and the settings are stored in the console) there’s a big changeover to re-rig for the evening Prom in time for an afternoon rehearsal. The evening Prom finishes around 9.00pm allowing time for another massive reset again for the Late Night Prom, which starts around 10pm. This is the kind of scenario where the recall facilities of a digital console really come to the fore, of course.

Main Arrays

Up until about 1986, the mic arrays in the RAH tended to be based on coincident pairs, although a Jecklin Disc arrangement was also used for a while. However, by the late 1980s the fashion had moved towards the use of spaced pairs to give a more commercial style of presentation that was strongly influenced by the timbre quality achievable with DPA 4006 microphones. Coincident pairs are great for mono-compatibility, but it seems more acceptable now to risk compromising the mono listener’s experience slightly to favour the stereo audience with a fuller, richer sound.

The Radio Stereo Pair bar, with DPA 4006 (below) and Schoeps MK2H (above) omni capsules facing forwards, plus a pair of Schoeps MK4 cardioids facing back into the arena.The Radio Stereo Pair bar, with DPA 4006 (below) and Schoeps MK2H (above) omni capsules facing forwards, plus a pair of Schoeps MK4 cardioids facing back into the arena.Not everyone agrees with that approach, of course, but Simon says the choice of mic arrays has evolved for a reason, and that they are unlikely to go back to using predominantly coincident pairs now.

The minutiae of the precise positions, types and number of suspended microphones on each sling is all detailed in a large folder which is updated every year with millimetre-accurate measurements, illustrations, and detailed construction plans. It’s a fascinating record of just how the rig evolves each year. For this year’s installation, several main stereo arrays were slung at various distances from the stage, and roughly three to four metres above it. In previous years there was a further option comprising a Royer SF12 stereo ribbon in a classic Blumlein X-Y format mounted just forward of the centre of the hall, but it was rarely used and so was omitted from the rig this year.

Starting with the most distant main array from the stage, a long stereo bar carries three sets of mics. A spaced pair of DPA 4006 omni mics mounted under the bar is the array that most of the Radio 3 balancers favour to deliver the main mix. Stephen Rinker, the balancer for the BBC Philharmonic Orchestra, asked for Schoeps MK2H omni capsules to be mounted directly above; these two systems have quite distinct sound characters, affording the balancers with different tonal options. A third, more closely spaced, pair of Schoeps MK4 cardioid mics on the stereo bar faces backwards to capture the arena atmosphere and audience.

Slung a few feet in front of these spaced pairs is a form of Decca Tree; the mic spacing is smaller than the original Decca Tree design and it uses three more DPA 4006s (all with foam windshields, as they can be susceptible to rising air currents) rather than the traditional Neumann M50s. This ‘Radio Tree’ is not used that often for the main sound, but it can be useful for upstage pieces.

The Radio Tree, comprising a trio of DPA 4006 mics.The Radio Tree, comprising a trio of DPA 4006 mics.Directly above the conductor’s podium are two more stereo arrays suspended from a single catenary wire. The lower array comprises a coincident pair of DPA 4021 cardioid capsules set with a mutual angle of 100 degrees, while the upper array is a near-spaced pair of DPA 4052 omnis mounted 250mm apart and about a metre above the cardioids. Apparently the crossed cardioids are particularly useful for small ensembles and solo violin or ’cello leads, while the spaced omnis are used mainly for extra presence on the strings as a whole.

Obviously, the idea is not to use all of these separate stereo arrays at the same time! Typically, one array will be selected to provide the core of the stereo mix for each event, the choice being determined by the scale of the orchestra, the style of music, and the kind of stereo presentation required. Generally some elements of the orchestra will require some extra focus, though, most of which comes from other mics slung above the orchestra. The appropriate compensating delays (1ms per foot of separating distance) are dialled into the console to time-align these ‘accent’ mics with the main pair.

Spot Mics

The suspended ‘accent’ mics start with a row of five DPA 4006 omnis (with foam windshields) called ‘the curtain’, which focus on the strings. These are all hung from a single catenary wire, and positioned about 2.5 metres above the front of the stage. To cover the back rows of the string section four DPA 4021 cardioids are suspended from another catenary sling, roughly halfway upstage. They are positioned quite low to maximise the string sound and minimise any wind and brass spill. A third swing even further upstage carries four more DPA 4021s angled towards the rear of the stage to focus on the woodwinds. There was some discussion as to whether to rig these this year, as some balancers prefer the greater flexibility of floor-mounted mics, but the TV sound team favour the flown mics.

Several concerts involve large choirs, and since 2009, more slings have been rigged towards the back of the stage to carry a number of chorus mics — four slings in total being needed to allow the mic positions to follow the curves of the upper and lower choir risers. These mics are mostly Schoeps MK4 cardioids, but there are also six Neumann KM184s for the upper choirs, and four Schoeps MK8 figure-8 capsules for the TV sound coverage (see below).

The TV ‘Schrub’ array before the mic cables are attached. The OCT mic trio comprises the two side-facing hypercardioid capsules and the closest centre side-address cardioid mic. The more distant cardioid forms a separate trio with the two downward-facing cardioids.The TV ‘Schrub’ array before the mic cables are attached. The OCT mic trio comprises the two side-facing hypercardioid capsules and the closest centre side-address cardioid mic. The more distant cardioid forms a separate trio with the two downward-facing cardioids.Two DPA 4006 and two Schoeps MK2H omnis are suspended directly from the roof in front of the organ to give a good spread of sound; some balancers also use these mics to add a sense of acoustic space sometimes, although that role is normally fulfilled by another pair of DPA omni mics on a sling towards the back of the hall. These are referred to as the ‘arena space’, and they are angled straight upwards. Another sling at the rear of the hall carries a pair of Schoeps MK21 wide-cardioid capsules facing forwards on a long stereo bar, and these are used to provide the rear channels in the experimental 4.0 surround stream.

The cables from the suspended sling mics are tie-wrapped to the catenary wires and run back to whichever side is closest, where they are connected to permanent stage boxes and cabled back to a room directly below Door 11, next to the BBC Compound. These mic-cable runs can be several hundred metres in some cases. Microphones on the stage floor stands are cabled to the nearest convenient stage box, there being eight of the BBC’s traditional seven-way units positioned across the stage width, with two at the front, three spread across the middle, and three more across the back. All of the mic lines eventually reach one of two Stagetec Nexus racks containing remote-controlled mic preamps and A-D converters, where the signals are digitised and sent over fibre-optic cables to the OB trucks. The TV-specific microphones are routed via two more separate Nexus rack boxes, and this affords the whole Proms project a great deal of failure-resilience, as the Radio and TV systems effectively serve as independent backups for each other.

Television Sound

Andy Payne, a former BBC TV OBs Sound Supervisor (and now freelance balancer with the Sound Alliance) specialises in classical music work, and has mixed most of the TV Proms broadcasts for more than a decade. When surround sound was first introduced to the Proms in 2005, separate surround and stereo mixes were created in different trucks by different balancers, specifically to ensure that the all-important stereo mix wasn’t compromised. Obviously, it’s too expensive and impractical to work that way in the long term, and Andy and his colleagues have gained enough experience now to generate only a live, 5.1 surround mix.

The stereo output required for the standard-definition broadcast is derived from a static downmix of the 5.1 signal within the OB truck, which Andy checks regularly, while the stereo downmix for HD viewers is derived at home courtesy of the transmitted metadata controlling the Dolby Digital decoder in the TV set. Naturally, the same downmix parameters (which, in essence, control the relative contributions of centre and surround channels in the stereo mix) are used in the OB truck and the transmitted Dolby Digital metadata.

The emphasis on maintaining the best possible downmix is because of the recognition that the larger part of the audience will actually be listening in stereo, regardless of whether they are watching the SD or HD broadcasts. Indeed, it is this ‘stereo priority’ requirement that has guided the development of the various mic arrays and mixing techniques currently in use, and consequently the need for completely separate main arrays from the Radio 3 provision.

One of the Stagetec Nexus mic preamp/MADI racks.One of the Stagetec Nexus mic preamp/MADI racks.It should be remembered that the TV and radio balancers are trying to achieve different things. The stereo Radio 3 mix traditionally has a glorious width and scale, and emphasises the character and spaciousness of the RAH. On the TV side, all those close-up television images inevitably demand a more focused sound than might be acceptable for radio. Moreover, in the early days of surround TV Andy found that a great surround mix didn’t always translate into a good stereo downmix, the latter often losing the sense of width and air. Fundamentally, he couldn’t find a way of making the stereo downmix work convincingly when the surround sound was built using the existing spaced-mic arrays favoured by Radio 3. Andy suggests that was because there are too many delay paths between the various Radio 3 mic arrays. For example, the Radio 3 ‘Arena Space’ omnis work very well in stereo, but when they were used for the rear channels of the surround mix, they produced pools of sound that didn’t join up nicely, and when folded down to stereo the delayed direct orchestra sound they inevitably captured resulted in unpleasant comb-filtering effects.

The Trees They Do Grow High

Careful experimentation over several years led to a clear preference for a full-size Decca Tree as the main TV array, not least because it naturally lends itself to the front LCR arrangement of a surround balance. It was also found that the optimum position was rather closer to the orchestra than the Radio 3 Tree, primarily because the TV mix needs more focus and clarity to balance the extra rear-channel ambience. A pair of omni outriggers either side of the TV Decca Tree are used to increase the sense of spaciousness for the stereo downmix, and this also helps to allow the Tree to be placed a little closer to the orchestra than normal.

Three Schoeps MK2H omni capsules form the TV Tree, each fitted with custom-made acoustic pressure equalisation (APE) spheres made from dense nylon. The outriggers are also fitted with these spheres, which are roughly two inches in diameter. The microphone diaphragm sits flush with the surface to mimic the arrangement employed in the Neumann M50 — the mic Decca used in the original Tree array. The effect of these APE spheres is to give some directionality at high frequencies, which turns out to be an important element for the stereo imaging. The three Tree microphones are supported from their own mic cables from a thin tubular metal wire frame attached to the catenary sling, but held in position relative to each other by a very thin vestigial wire frame which is invisible to the TV cameras.

The rear-channel problem was solved by employing a ‘Hamasaki Square’ comprising four Sennheiser MKH30 figure-8 mics positioned at the corners of a large virtual square located several metres behind and above the Radio 3 spaced-omni array. These figure-8 mics are oriented sideways with their nulls facing the stage, so that they capture only reflected and ambient sound. With nothing direct from the stage at all this arrangement completely avoids any comb-filtering problems in the stereo downmix. Stylistically, the TV surround sound mix needs quite a lot of energy in the rear channels, but Andy doesn’t want this to be music from the stage! The Hamasaki Square array picks up a lot of ambient sound and audience reaction, and it folds very nicely into stereo.

Out Of Sight

It seemed to me that the TV Tree and Hamasaki Square arrays are noticeably more elegant and camera-friendly than the old-school stereo bars and Decca Tree frames used in the Radio 3 installation. Not that the main stereo arrays get caught in shot very often, but as Andy points out, any flown hardware can be quite intrusive to the cameras, and any further additions need to be handled as sympathetically as possible. Of course, it’s also difficult to change things radically when the Radio 3 coverage is shared between 10 SMs, all with their own ideas and preferences; Andy only has to argue with himself about how to cover things for TV!

Checking the alignment of the Radio Tree.Checking the alignment of the Radio Tree.Working closely with Steve Higgs of Origin Audio to design, construct, and fly the arrays, Andy’s approach is based on the fact that slim, vertical, matt-grey mic cables are almost invisible on camera, while the traditional steel catenary slings tend to catch the backlights and are far more obvious. Consequently, the TV sound slings are rigged rather higher than the Radio 3 slings to keep them out of shot, and the mics are dropped further from them on slim grey Schoeps cables which have Kevlar cores and so can be used to suspend the mic arrays quite safely. The capsules are held in the correct relative positions by vestigial wire frames which, again, are almost invisible to the cameras.

Another good example of this approach is an array positioned almost directly over the conductor a few metres in front of the TV Tree, known as the ‘Schrub’. This ‘mini-tree’ of Schoeps mics combines two three-mic arrays. The first is an Optimised Cardioid Triangle (OCT), which comprises an MK4VXS centre cardioid capsule positioned just 80mm in front of two MK41 super-cardioid side-facing capsules. This array is used to help ‘grip’ the strings if needed, while retaining good imaging. The second mic trio is a triangular arrangement of MK4VXS cardioid capsules, which is useful for drawing out the front-desk string solos, as well as for smaller ensembles.

I mentioned earlier the Radio 3 choir slings which position mics relatively close to the choir to minimise orchestral spill; the down side of this technique is that a lot of mics are needed to prevent individual voices standing out. In contrast, Andy prefers a more distant technique using just four mics, with each ‘seeing’ a much larger body of singers. To minimise spill from the orchestra he uses Schoeps MK8 figure-8 capsules positioned with their nulls aimed at the orchestra below. To help cover the outer edges of the upper choirs, a pair of Schoeps CMIT-5U gun mics are also used, suspended on 1.5m drop arms from the sides of the lighting truss. This technique would be quite impractical with most interference-tube gun mics because of their notoriously poor off-axis coloration, but the CMIT is unusually clean off-axis, and it works surprisingly well in this application.

The balance obtained by the Decca Tree and Hamasaki Square is usually pretty good, apparently, but is normally supplemented with the shared Radio 3 woodwind sling mics and some on-stage mics. Again, Andy generally prefers a more distant ‘zone mic’ approach rather than the close spot mics favoured by the Radio 3 balancers, although this inevitably means picking up more off-axis sound. Off-axis coloration is something of which Andy is very aware, and his solution is to employ omni and figure-8 capsules wherever possible, as they tend to suffer less from off-axis coloration than cardioid mics.

Most of the televised Proms are pre-recorded, and on those occasions Andy mixes the in-vision presentation elements as well as the orchestral sound. However, for the live or ‘as-live’ (meaning delayed) programmes, the programme presentation aspects are handled in the TV production OB truck by a second sound supervisor, in a conceptually similar arrangement to the Radio 3 Loggia operation (see ‘Loggia Operation’ box).

Summing Up

It is fascinating to compare and contrast the Radio 3 stereo and surround mixes with the television 5.1 and stereo mixes. All are superb in their own way, of course, but also deliberately very different for the reasons explained above. If you get the chance to listen to a few Proms concerts I urge you to do so as they represent the state of the art in live classical broadcasting today.

Thanks to Simon Tindall, Simon Hancock, Andy Payne, and all of the sound crew working in the RAH, for their assistance in preparing this article.

Promenade History

The Promenade Concerts started in August 1895 and were conceived by Robert Newman, the manager of the Queen’s Hall in London. Newman was concerned that audiences always dwindled in the late Summer period, and he invented the Promenade Concerts as a way of drawing in new audiences and revenue. His aim was to run nightly concerts through which he could “train the public by easy stages”, starting with popular light music, and then “gradually raise the standard” until he had created “a public for classical and modern music”. Mr. Robert Newman’s Promenade Concerts, as they were known, lasted around three hours. To attract the widest possible audience, ticket prices were 80 percent lower than normal and smoking and refreshments were permitted during the concerts!

Checking the length of cable drops from the catenary to the capsule.Checking the length of cable drops from the catenary to the capsule.A little-known conductor, Henry Wood, was appointed for the entire season to help keep costs down, and he continued in that role for 49 years up until his death in 1944 at the age of 75. Wood gradually evolved the Proms’ repertoire into the form it broadly follows today, with an emphasis on promoting a wide range of composers’ works as well as supporting young talent. Although Newman’s pioneering role has largely been forgotten, Sir Henry Wood’s name has become inseparable from the Proms festival.

The BBC became involved with the Proms in 1927 following the withdrawal of music publisher Chappell & Co as the event’s main financial supporter. For the following three years the BBC broadcasts featured “Sir Henry Wood and the Queen’s Hall Orchestra”, but after the BBC’s Director of Music Adrian Boult formed the BBC Symphony Orchestra in 1930 — the first permanently salaried orchestra in London — the Proms always featured the BBC SO.

For their first 50 years, the Proms were based at the Queen’s Hall, then London’s principal symphony concert venue. The QH, which opened in 1893, was located in Langham Place, adjacent to the All Souls Church, on a site now occupied by the Saint George’s Hotel, just a few hundred metres from the junction of Regent and Oxford Streets. At the outbreak of World War Two, the BBC SO was moved to Bristol as a contingency to minimise disruption to music broadcasts, and the BBC withdrew its support of the Proms at the same time. Not perturbed, Henry Wood continued the 1940 Proms festival with the London Symphony Orchestra, backed by the Royal Philharmonic Society. Unfortunately, the intensity of German bombing over London eventually forced the Queen’s Hall to close just four weeks into the season, curtailing the Proms. Despite some bomb damage in December 1940, and again in April 1941, the Queen’s Hall continued to host classical concerts, but sadly, in May of that year an incendiary bomb reduced the hall to a smouldering ruin overnight. All that survived was a bronze bust of Sir Henry Wood.

The TV Decca Tree outriggers before installation, fitted with custom acoustic spheres.The TV Decca Tree outriggers before installation, fitted with custom acoustic spheres.The only other hall in London able to accommodate a full symphony orchestra at that time was the Royal Albert Hall, and so that’s where Wood relocated for the 1941 season. The BBC SO returned to London in 1942 and the BBC renewed its support of the Proms, which have continued at the RAH ever since. That bronze bust of Sir Henry Wood spends each Proms season installed on a podium in front of the organ loft in the RAH — I watched it being put carefully into position and bolted down during my visit.

A Government committee considered rebuilding the Queen’s Hall in 1954, but it was decided that doing so would detract from the audiences and funding of other concert halls around London, specifically the Royal Festival Hall, which opened in 1951 as the new premier symphony orchestra venue in London.

Slings & Roundabouts

Slinging microphones above the public is not a trivial exercise from a health and safety perspective, falling under the ‘Lifting Operations and Lifting Equipment Regulations 1998’, otherwise known as LOLER. This legislation basically says that all equipment must be fit for purpose, and installed by competent people in a safe manner. In practice, that means that the catenary wire must be steel cable, not rope, and that the cable, shackles and fittings must all be suitably rated for the loads involved.

The wire slings employed for the Proms are all custom-made for use in specific positions within the RAH, and comprise 5mm steel cable with professionally swaged thimbles at the ends. Several also have karabiner links within them at strategic positions to facilitate the hanging of short wire links to support stereo bars and the like.

Each catenary sling is checked and assembled on the Arena floor, with every mic and cable being carefully tested and auditioned before rigging using a Yamaha 01V96. Where microphone capsules have strong, non-detachable cables, they are hung directly from the catenary wire, secured with plastic tie-wraps or, in the case of the Schoeps mics, with bespoke cable clamps. The clips on XLR connectors are not deemed to be adequately secure on their own to suspend microphones above the public, so additional methods are employed such as 1mm safety wires screwed directly to the mic body, or secured with jubilee clips.

The BBC Proms rigging manual detailing the two conductor pair mic arrays.The BBC Proms rigging manual detailing the two conductor pair mic arrays.Preamp bodies and mic cables are tie-wrapped to the catenary wire, with a few short cable loops left at the mic end to permit adjustments once the rig is flown. Stereo bars and other mounting hardware all have secondary safety wires attached so that, should they spontaneously collapse, nothing can fall on the audience below. Where relevant, ensuring that the mic capsules face the correct direction is taken care of either by rotatable capsules or stiff coiled-wire ‘pig’s tails’.

When a catenary has been assembled and is ready for slinging, the whole rigging team carry it on to the stage, being careful not to damage the dangling microphone capsules in the process. Ropes are then lowered from the high-circle mounting points, attached to each side of the sling, and hauled back up. This is the most dangerous phase of the installation, so there are always two people on each side doing the hauling, both with their hands permanently on the rope until the sling is safely shackled to the mounts.

A close-up of a catenary sling attachment, showing the 5mm catenary wire passing through the Techni-Grip 50 clutch which is fixed to the mounting rail via two quick-link shackles.A close-up of a catenary sling attachment, showing the 5mm catenary wire passing through the Techni-Grip 50 clutch which is fixed to the mounting rail via two quick-link shackles.When I was involved in rigging the RAH decades ago the catenary thimbles were shackled to a chain, and the chain wrapped around a rigging bar fixed to the wall. Tensioning the cable and adjusting its height was done by deciding which chain link to slip the quick-link shackle through, which was difficult and time-consuming. The current setup is much more elegant, using Techni-Grip Type 50 cable clutches. The Techni-Grip mechanism allows the catenary cable to be pulled through easily in one direction, but it can only be released in the other by manually pushing the clutch collar inwards. This makes adjusting the cable tension and height very quick and easy, and once positioned correctly, the clutch collar is screwed down to prevent any further movement. The eye nut on the Techni-Grip is secured to an eye bolt on wall-mounted rigging bars with quick-link shackles in the usual way, and the surplus catenary cable is also secured to the mounting bar with a padlock as a safety backup.

Aligning the mics across the stage is made easier with a small masking-tape flag attached to the centre of the catenary cable. By taking in or releasing cable from each side, the centre of the sling can be aligned with the centre-line of the stage to ensure the attached mics are positioned correctly across the stage width. The precise height of the mics above the stage is then checked with an extendable pole, and adjusted by taking in or releasing cable equally on both sides.

Loggia Operation

In addition to crafting the music mix in the OB truck, most of the classical SM team work on the live broadcast programme mix from a Loggia box just off the left-hand side of the stage. This role is multi-faceted, as it includes recording interviews with artists during the day, and editing that material using a SADiE DAW for subsequent play-out within the programme during the intervals. This can be quite a full-on job, and Simon explained that the separation of the music-mixing and programme-presentation roles is a rare, but welcome, luxury. Although a similar arrangement is employed for broadcasts from the Royal Opera House, the music balancer normally has to handle the presentation side of things too, which includes liaising with and taking cues from Broadcasting House, greatly increasing the workload.

A Yamaha DM1000 console in the Loggia. A UPS unit is visible under the desk on the left, with an audio interface for the playout laptop above. Various communications units and a Reidel talkback panel can also be seen.A Yamaha DM1000 console in the Loggia. A UPS unit is visible under the desk on the left, with an audio interface for the playout laptop above. Various communications units and a Reidel talkback panel can also be seen.Inside the cramped Loggia, a Yamaha DM1000 digital console is used to generate the Radio 3 broadcast output, combining the presenters’ mics with the stereo orchestral mix from the OB truck, and any pre-recorded programme segments during the intervals. Monitoring tends to be done on Sennheiser HD600 headphones, partly to exclude the direct hall sound, but also because the wall-mounted Genelec speakers tend to sound boxy in the cramped space. The pre-recorded interval items are stored on a server at the RAH (which is tied into the audio servers at Broadcasting House), and played out from a laptop using CoolPlay, a very basic audio playlist application written especially for BBC News, which is ideal for organising and playing programme inserts.

The presenters use Beyerdynamic DT770 Pro headphones and have a choice of microphones, with the favoured option being DPA 4006 omni mics fitted with two foam windshields. Alternatives include Neumann KMS105s and Sennheiser MD211s. Standard practice for live broadcasts requires main and spare microphones to be available for the host presenter and guest.

Should there be a problem with the digital link carrying the music mix from the OB truck, the Loggia desk also receives an analogue backup, plus a feed of the TV sound mix and direct splits from some of the main stereo mic arrays in the hall which can be used in an emergency. A feed from the RAH’s PA system is also available as an alternative backup mix for the heavily amplified shows. A Reidel talkback system allows direct communications with pretty much anyone and everyone on-site and in the BBC Compound, and even to the Royal College of Music across the road behind the hall, where many of the interval features are recorded.

The Radio 3 Stagetec Aurus digital console. A sliding score shelf covers two control sections on the left side of the desk. Geithain RL901K monitors peer over the console.The Radio 3 Stagetec Aurus digital console. A sliding score shelf covers two control sections on the left side of the desk. Geithain RL901K monitors peer over the console.The broadcast output is sent back to Broadcasting House as linear, 16-bit audio via a 2Mbps E1 data circuit using an APT Worldnet codec. This is the standard technology used for most Radio 3 concerts in Greater London, with permanent E1 circuits also installed at the South Bank, Cadogan Hall, Wigmore Hall, the Royal Opera House and the Barbican. The same data stream also carries a 7.5kHz ‘four-wire’ (send/receive) coordination circuit for communications. In previous years a backup music circuit was provided via ISDN, but it’s now via an IP stream on a 25Mbps broadband connection.

Mixing The Proms

Simon Hancock’s approach to mixing the Proms starts with the default setup previously stored in the Aurus console, which is intended to give a decent sound straight off using the spaced omni mic array, with contributions from most of the flown accent mics preset to sensible starting levels and with the correct panning and alignment delays dialled in. This default setup doesn’t include any stage mics, of course, but it makes setting up pretty quick, maximising the time available to fine-tune the mix.

A defiant Sir Henry Wood inspects the rubble of Queen’s Hall after its destruction by German bombs.A defiant Sir Henry Wood inspects the rubble of Queen’s Hall after its destruction by German bombs.The Aurus console is set up with all of the main stereo arrays on fader layer B, and all the flown and stage mics on layer A. The reason is that once a main array has been selected it doesn’t normally need to be adjusted and can therefore be on a hidden fader layer (it’s normally allocated to its own stereo group anyway). In contrast, the individual spot and flown accent mics are adjusted continuously and so must be accessible at all times. Despite several ‘space’ and ‘ambience’ mics being flown in the hall, a four-input Lexicon 960 digital reverb is also available on the desk and used to fill out the mix, since the RAH becomes surprisingly dry with a full audience! Where needed, dynamic management is mostly applied through careful fader control following and anticipating the score, but Simon usually sets up a little compression on the desk output just to catch any errant peaks. Typically, he sets a ratio of 1.6:1 with a threshold of -10dBFS, so it really is very gentle!

For the experimental 4.0 radio surround mix, the normal stereo mix is used for the front channels, and the MK21 and DPA4006 ‘arena space’ mics are used to create the rear channels. A separate feed presenter mic signal is routed to the front of the surround mix for Proms where there is on-stage presentation. This experimental streamed surround mix is very different in approach and style to the full 5.1 TV surround mix, and was arrived at by experimenting with multitrack recordings from previous Proms seasons.

On The AirRegarding the stage spot mics, for the First Night Prom Simon was planning on supplementing the flown rig with around 15 stage mics comprising two brass mics, a horn mic, a couple on the harps, two timpani mics, four mics for the solo singers, and possibly some bass mics — although he says bass is not usually a problem and often there is too much in the RAH rather than too little. He also added two extra chorus mics on stands because, although the back of the stage and upper choirs are well covered by the slung mics, the mid choirs can be a bit left out.

Published November 2014