Sound Reinforcement
Almost every complaint an event receives about its sound is a planning failure rather than a mixing failure. By the time an engineer has his hands on the console the outcome has largely been decided: by where the stage was pointed, by which boxes were hired, and above all by what was written in the licence application eleven months earlier. MGH therefore treats sound reinforcement as an environmental and regulatory discipline that happens to produce music, and we would rather have the argument with a client in October than with an environmental health officer on the Saturday night.
MGH provides sound reinforcement and environmental compliance support for public events. Personnel identities, storage locations, staffing and event assignments are withheld.
Array and delay design
Every system begins as a prediction, not a hire list. Site survey data, stage position and the licensed audience footprint are modelled to give coverage across the listening plane, and we design to a tolerance of ±2.5 dB broadband across 90 per cent of the ticketed area, measured at 1.7 m. A main hang will hold its specified level to roughly 62 m before the arithmetic stops flattering it; beyond that, adding cabinets at the stage buys distance at the cost of everything the neighbours hear.
The crossover point is unromantic and easy to calculate. Once the required throw exceeds about 70 m, a delay ring is cheaper than the four to six further cabinets per side needed to reach the back. It is cheaper in hire, cheaper in rigging, and very much cheaper in off-site level, because a delay tower radiates its energy into the crowd rather than over the boundary. Rings are typically spaced at 58 m, timed to the main hang with an additional 12 ms of Haas offset so that the image stays on the stage.
Noise propagation and licensing support
MGH prepares the noise chapter of the event management plan and, where the works warrant it, submits prior consent under section 61 of the Environmental Protection Act on the client's behalf. Propagation is modelled to the agreed monitoring positions under worst-case downwind conditions, since a 3 m/s tailwind will reliably return 4-6 dB that a calm-day prediction promised you had lost.
| Notional position | Description | Agreed limit |
|---|---|---|
| MP1 | Boundary of Ashfield Lane, 780 m from stage | 65 dB(A) LAeq,15min |
| MP2 | Rear garden, Glebe Cottages | 63 dB(A) LAeq,15min |
| MP3 | Village hall car park, downwind sector | 55 dB(A) after 23:00 |
Attended monitoring is carried out by a competent person from 16:00 until curfew, with readings logged at 15-minute intervals against wind speed, direction and observed source. The curfew is a hard stop, not a target: main stage music ceases at 23:00, ancillary areas at 00:30. The signed monitoring log is delivered to the local authority by 10:00 the following morning, whether or not anybody has asked for it.
A standing position. MGH has, on eleven occasions since 1996, been asked by a client to exceed an agreed noise limit for the duration of a headline set. On each occasion we have declined, and on each occasion we have declined in writing, with a copy to the licence holder. We expect to go on doing so. Clients who find this inconvenient are respectfully invited to discuss it before contract rather than at 22:40.
NETLINK™ radio talkgroups
Production communications are supplied as a managed service rather than a box of hired handsets. A standard NETLINK™ deployment provides 16 talkgroups: production, stage, monitors, rigging, transport, medical, stewarding and a dedicated incident group. Site coverage is achieved by a licensed repeater on the highest available structure and, where the ground demands it, one or two fill sites surveyed the previous month. Frequencies are licensed for the event dates in MGH's own name. The incident talkgroup is patched directly into the GOLDCELL™ event control room, so that a sound problem which becomes a crowd problem does not first have to become a telephone call.
RF co-ordination
Radio microphones, in-ear monitors, talkback and the security radio plan share one spectrum and one co-ordinator. MGH produces a channel plan for the whole site, runs a third-order intermodulation study across all users, and publishes the result as a single frequency register that no department may depart from without asking. At our largest engagement we co-ordinated 214 simultaneous channels across eight stages, four broadcast trucks and the stewarding network, with two hours of pre-show sweeps and a spare-channel reserve of 11 per cent held back for the day itself.
Typical system designs
| Audience | Array configuration | Delay positions | Control positions | Crew |
|---|---|---|---|---|
| 2,000 | 8 boxes per side, ground-stacked sub array | None | 1 (front of house at 24 m) | 4 |
| 12,000 | 14 per side flown, 4 out-fill, 16 subs in cardioid arc | 1 ring, 2 towers at 58 m | 2 (FOH and monitors) | 9 |
| 68,000 | 18 per side flown, 12 side-hang, 8 front-fill, 32 subs | 3 rings, 10 towers to 174 m | 4 (FOH, monitors, RF, noise) | 22 |
Worked examples, including the 2002 Ashfield deployment and the Braithwaite Park Proms broadcast, appear in our case studies. A printed system brochure is posted by first class post on request; to discuss a licence application, an existing s.61 notice or an RF plan, please contact us or telephone Production on +44 (0)1582 496 200.
Page last updated 27 January 2003.
