The context
Sound application for live music did not evolve from a history with a high demand for realism or fidelity, and this should be approached with 'in context'. It is essential to understand the history behind sound for live production, to go beyond the separate mono PA trend the entertainment industry trapped itself in.
Sports are the largest of spectacle events. The collective energy and roar of crowds in large reverberant stadiums and auditoriums, drives the adrenaline of excitement, similar to addiction. The majority of audiences go to see (not listen to) sport and live musical productions, including opera, as spectacle events. Traditionally, entrepreneurs see lighting and image as important, not sound fidelity. Sound budgets are often limited to 10% of production cost.
Not all performers express interest in how they are heard by an audience. This they believe should be managed by others. However, stage monitoring is understandably a performers prime concern. The separate mono PA of limited fidelity has become the simplest cost alternative, for audiences to hear live music productions.
Above is an example of technology reaching the limit of what can be technically achieved from a line-source PA system, for sport and live music productions.
The speaker stacks are spread around the stadium or auditorium, as close as possible to the audience. Technical emphasis is not on dynamic fidelity or realism, but for the whole audience to hear sound almost at the same level through out the venue. In its own direction, this latest technology (line-array) has been an astounding technical achievement, enabling sound to be heard equivalently, throughout large reverberant environments.
But live music productions are pre-mixed and compressed, often only heard in mono, from each nearest speaker stack. The result for music, bears little or no resemblance to how the production would sound directly, up close or on the stage. The sound system acts as a barrier, separating the performance from the audience. Sometimes the audience only see the performance on large video projection.
Above is a pic of the 1970s Greatful Dead sound system, that represents the alternate (opposite) principal, of each instrument and voice being amplified and heard from, separate, stage sound systems. The audience experience startling dynamic clarity, similar to being up close, or on stage, with the musicians.
In the early 1970s there were a handful of innovative sound companies, including Lenard Audio, that were developing variations of this principle . This direction was not adopted by the entertainment industry, it was seen as too difficult to implement. It is essential to understand the history, behind sound, for live music production, to go beyond the separate mono PA trend, the entertainment industry trapped itself in.
Historical Context
In each generation, a percentage of rebellious youth culture, is symbolised by aggressive, loud, harsh, distorted noise. Rock music evolved from Blues, the music of the streets. Most musos' of the 50s were poor. PAs and guitar amps were made to a budget. Not all technical principles of sound system design were well thought out.
In 1964 The Beatles toured the world, using their Vox 30 Watt, instrument amps. They often used small house PAs, consisting of 12in speakers in columns, driven by 100 Watt amps (if they were lucky). The screaming audience completely drowned them out. In many cases the band was not heard at all. They never did concert tours again. This sent a strong message to entrepreneurs that sound quality had no effect on audience attendance. Prior to this period bands only had small amps and simple lighting, often with only a single spot. Instruments were the main drive and vocals were separate.
The majority of PAs in the early 60s consisted of columns of 12in speakers. (seen in the background of the pic on the right) Bands often did 3 gigs a night, traveling in unregistered Kombis or transit vans; this restricted PAs to two 4 x 12in columns, similar to the size of instrument amps. Few bands operated as an efficient business. Large horn-loaded PA systems were economically out of reach.
The Transition
Then came the transition period of the PA, which began to dominate as the main system, with both instruments and voices adapted within it. But the result was a compressed sound, devoid of dynamic expression, fidelity and realism. PA's were at an impasse. For a PA to be effective it had to be at least 4 times the scale of the instrument amps, and fully active to achieve fidelity. Many bands believed that venues should assume responsibility for sound, but this did not evolve.
Many early sound system manufacturers, were conservative, from a previous generation of the 40s and 50s, influenced by religious, country or jazz music. In the early 60s, many manufacturers were horrified, by the sex-crazed, drug-driven, anti-war/religious, rock-musos', who drove their sound systems into hard distortion. When these sound systems were first designed, it was inconceivable they would be used this way. The technical limitations of these systems, characterised their sound, enabling them to distort easily, exactly what many 60s rock musos' wanted.
The ironic humour, was that some manufacturers reacted by making warranties void, if sound systems were driven at full power. Other (well known brand) manufacturers threatened to cut off retailers, who sold their sound systems to bands that played 'music of the devil'. The parody of this historical contradiction has been rewritten, to fit mythical beliefs, that brilliant designers, created these systems for what 60s and 70s rock bands' wanted.
Many hard rock and pop bands were musically unprofessional, driven by stage theatrics, copying 'heavy rock and metal' trends, in the styles of the Stones, Sex Pistols, Black Sabbath, Led Zeppelin etc. The drug image of many bands, assisted their promotion, with full support of record companies and media exposure. This later evolved into branches of rap and techno. This drug culture also dominated the new emerging live sound re-enforcement industry.
Most concert sound systems consisted of horizontal clusters of ugly black boxes (adapted from cinemas) that produced harsh, distorted, unintelligible sound. This image also included the entourage of, multi set of keys, stoned, roadie sound engineers. Through ignorance they placed speakers facing directly forward, against side walls, which increased room reflections, lobeing, and comb-filter distortion. They have gigantic mixing consuls, with racks of effects, which they place in the middle of audiences, with desk-lights on themselves. There favourite effect is to add compression to everything. Many roadies' wanted to be musos', and therefore, make their favoured instrument or singer loudest, and turned off who they dislike. The bands constantly complain about their on-stage monitoring, but take little interest in how they are heard by the audience.
By the late 60s, fusion music, including a % of pop, rock and R&B, performed with a high level of music skill, also became popular. Santana, Frank Zapper, Chick Corea, Herby Handcock, Eagles, Yes and the Motown label, etc, to name a few. This music inspired the development of full fidelity, large-scale, active PAs. But music of high technical skill (including classical) has limited support from media and record companies. Considered too complex for mainstream audience enjoyment.
By the late 70s the world had changed. The era of the 60s which created free love, and the greatest diversity of music ever known, had come to a close. The 80s became known as the era of entrepreneurial greed. A plethora of questionable audio recording engineering schools flourished. Media editorial became advertorial, particularly in audio journal's. Many major brand name sound systems, were made cheap as possible, but became expensive to purchase. Brand names became marketed as having magical powers (especially cables). Model-number junkies, dominated the industry.
Ceiling Clusters
By the 80s, moving sound systems from the floor to the ceiling became the trend. This gave extra floor space for staging. Reverberation and echoes from walls and ceiling is multiplied if the speaker systems are incorrectly placed, which most were - and still are. Organising speakers into semi-cylindrical vertical clusters has the potential to reduce some problems previously described. Fidelity improves if sound appears from a single source. But there is a maximum size clusters can be arranged, before distortion becomes excessive.
Above is a typical performance graph, of popular (passive) speaker cabinets used in clusters. Some expensive (active) speaker cabinets, were designed for cluster arrangements, minimising lobeing between speakers. Some clusters were spread through-out the auditorium, others were placed in centre position above stage (above right). On stage instrument amps became smaller, and fold-back monitoring increased in complexity. The modern trend was for the audience not to hear sound form the stage. All sound dominates from the ceiling cluster systems. The PA now behaves as a barrier, separating audience from performance.
Most performances are mixed in mono. The irresponsible trend of using excessive compression for recording, also dominated live music. Compression changes the character of voices and instruments away from sounding natural. Without hearing direct sound from the stage (comparison), it is difficult, if not impossible, to know if a performance is mimed. In some events entire orchestras mime.
The development of full fidelity, large-scale active PAs, inspired by fusion music in the late 60s early 70s, was left incomplete. It became too difficult to innovate new designs, in what had become a technically illiterate industry, dominated by commercial interest promoting hard rock, techno, and vacuous teeny pop. The emerging IT industry consumed the best technical people. The live sound re-enforcement industry was left to flounder for the next 20 years. Loud harsh distorted sound remained the primary symbol of live music.
Line Source Systems
1990s. The application of line-source systems allowed entrepreneurs to market to larger and larger events. Originally line-source speaker systems were confined to small columns, seen in churches, gymnasiums, schools, etc. Application limited to announcements and background music.
Line-source sound systems, for large venues, had been understood since the 50s. But the limited efficiency, of a large line-source, compared to the higher efficiency, of a well designed, full exponential horn system, was not acceptable at that time. Especially for cinemas.
Why the change?
(1) Large power amps became readily available, and cheap.
(2) Technical problems, of rigging, and component alignment, were solved.
(3) Passive social acceptance over 2 generations of listening to limited fidelity.
The theoretical advantage of a line-source system, is that the whole audience can hear the sound equally. Sound appears to remain at a similar level, as the distance from the line-source increases. The inverse square law is reduced, and horizontal directivity improved. Line-source systems are the best solution, for large difficult reverberant environments (sport stadiums etc). But many line source systems are being marketed as the best solution for every imaginable application. They are not the best solution in excellent acoustical environments, where fidelity is the major requirement. These reasons are explained on the previous page 'Horn Systems'.
Live Sound Problems
Mixing a whole band or orchestra through a PA system, distorts and colours the performance by the system limitations, inter-modulating and inter-cluttering the instruments and voices, sometimes into an un-intelligible mess.
- Lobeing distortion (wave-length distance between speakers of horizontal stacks)
- Comb-filter distortion (path-length differences between left and right speaker stacks)
- Inter-modulation distortion (passive speaker systems and cheap speakers)
- Reverberation and echoes from walls and ceiling.
- Mixing everything in mono.
- Incorrect use of compression limiting.
- Excessive numbers of mics, especially on drums.
(1) Lobeing distortion is heard as peaking and dipping of mid and high frequencies, around each speaker stack. The problem is caused by speakers being stacked horizontally, separated by more than wave-length distances, at different frequencies, between speaker components. The greater the number of speaker cabinets, the worse the problem becomes. As the frequency rises, the wave-lengths get shorter, increasing the problem, causing the overall hi-frequency energy and intelligibility to decrease.
(2) Comb-filter distortion is heard as phase colouration and cancellations in the music . The primary cause is path-length differences between the left and right speaker stacks. Sound travels at approx 344 meters per sec (1ft per milli-sec). Sound to the audience arrives at different times from each speaker stack, and this causes cancellations throughout the frequency spectrum. The cancellations increase as the frequency rises, causing the overall hi-frequency energy and intelligibility to decrease. This problem is exaggerated when both speaker stacks are mixed in mono. Also the further speaker stacks are from each other, the worse the problem becomes.
(3) Reverberation. Echo is reflected off walls and ceiling, which appear as secondary multiple sound sources. Reverberation and echoes decrease intelligibility and hi-frequency energy. This problem is exaggerated when speaker stacks are faced into or forward against side walls.
(4) Compression-limiting should only be used as a production effect, scored and rehearsed with the musical arrangement. Compression-limiting should never be used on the on the sound system as a whole. A negative example is when a small low fidelity sound system is turned up very loud and then compress-limited, solely to ovoid peak amplifier distortion and protect cheap speakers. Another negative example is the wrong teaching at questionable audio schools. Students are taught to put compression-limiting on everything. This behaviour was only appropriate in the past, when recorded music was compression-limited to fit within the small dynamic range of AM radio TV broadcasting. Continuous compression-limiting in live performances causes the music to sound flat and lifeless.
Note. Combination of all the above, multiplies the problem, decreasing intelligibility and hi-frequency energy. Increasing the number of speaker cabinets, also increases the problems, so much so, that in many cases, acoustical cancellations are so great, overall sound energy to the audience decreases.
Live Sound Basic Applications
(A) Concert Production
The musicians and artists should be autonomous on stage, in balance with each other first. An opera singer can perform without a sound system to an audience of thousands (in a good acoustical environment). Live production is exciting, because of the spontaneous and dynamic expression of the performance. Excessive sound amplification restricts natural expression and reduces audience enjoyment.
The speaker system should have focused directivity to the audience across the whole musical range, shifting the apparent acoustical centre forward by 6db. The overall power level can also be amplified by 6db for expression and detail. The combination of system directivity and increased power should give approx (+10db) double loudness and presence, with full fidelity and realism. Wherever possible mixing should be from the centre in stereo, where sound from left and right intersects, and at a distance no further back than where the direct sound from the speakers becomes equal to the reflected reverberant energy of the room (critical distance).
Apparent acoustical center. The first objective is to shift the apparent acoustical center of the performance into the audience. The performance should acoustically appear to come from half the distance than it actually is. The performance should not appear to come from the left and right speaker stacks, but from a sound field that is projected into the audience by the speaker stacks. This may appear difficult but it can be achieved, except in excessive reverberant environment. Each separate left and right speaker stack must be capable of reproducing equally the full fidelity and dynamic power of the performance, without distortion or the use of compression limiting. This means that the acoustical gain of the sound system must be capable of unity with the performance.
Unity acoustical gain means that the sound system must be capable of reproducing the same dynamic sound energy (per unit area) as the stage performance (or greater). In theory each speaker stack should be capable of an unrestricted dynamic power response, enabling it to acoustically mirror the stage performance, one to one. Acoustical gain above unity is used for special effect, to make an instrument or voice appear to stand out from the performance. In extremely large venues where it is not possible for all the audience to be within reasonable proximity of the stage, then the added speaker systems should be identical, and positioned to minimise overlap.
Cross monitoring is the most effective means by which performers can hear themselves. The monitoring system should replicate as close as possible the main system, enabling the performers to hear themselves similarly with their audience. A wedge monitor should only be used where it is not possible for a performer to hear cross monitoring.
(B) Stage production High-energy
The above drawing represents the alternate principal, of each instrument and voice being amplified and heard from, separate stage sound systems. If well done, the audience can experience startling dynamic clarity, as being up close or on stage with the musicians. This direction requires a high level of production skill, performed by professional musicians.
The stage instrument systems are independent as well as being interconnected, to act as cross-monitoring for each others instruments and vocals. The cross-monitoring into each instrument system is approx -6db below what each instrument system is primarily used for. An example being that vocals can appear from the guitar and key-board systems, but at approx -6db below the level that the instrument system is primarily used for.
This procedure gives an automatic bal lance for each musician to hear themselves, in proportion with the other instruments. The bass guitar and bass drum (kick) including other information below 100Hz from other instruments, is all reproduced through the dual bass instrument system.
The vocals and percussion are reproduced through the high powered 3 way active 'stereo system' on either side of the stage. The vocal-percussion speaker system does not need to produce sub-bass (below 60Hz). The vocal-percussion system can also be used for special effects. The system should be spaced as close as practical (left-right) to minimise time alignment difficulties in stereo imaging, and to avoid short percussive delays being heard by the musicians. Depending on the inward angling of the vocal-percussive system this can also provide cross-monitoring for the performers at the front of the stage.
Club Venues
(A) Many club venues are acoustic nightmares with inadequate stage space or access. The obsession to fill the venue with sound only creates further problems with echo and reverberation. Some stages are reverberant boxes, and the moment microphones are turned on they feedback. Often this problem is compounded by the use of wedge monitors, reflecting sound from the low stage ceiling and rear stage wall. The band could spend a few extra minutes set up time, to put anything against the rear stage wall to provide acoustical absorption, instrument cases, boxes, old curtains etc (forget the looks).
A band that can hear themselves without feedback and are comfortable, will perform better (cook). If the band 'cooks' the audience will have a more enjoyable time, regardless of the acoustic problems. Therefore it is more important for the sound system to be best for the band, if a choice has to made. Also not all the audience want to be deafened, and many prefer to sit in quieter spaces if available.
One good but rarely used solution is to put the sound system in front, but cross facing back to the stage. The band and the audience nearest the stage now hear the main sound system. The monitoring system is faced outward from the same position, to the audience at the back of the venue. There are many variations of this method, all that matters is to think creatively.
(B) Dance clubs (pre-recorded music) often have the same acoustic problems as live music clubs. One of the best solutions is to create an intense sound field in the center of the room. By facing the sound system inward from 4 positions keeps the sound field concentrated and minimises echo reflections from walls.
Most dance music is percussive, and sounds best in non-reverberant environments. Also it is important not to have the speaker stacks too far from each other. Time alignment of the percussive notes between the speakers can become a mess, if speakers are too far apart. Sound travels at 344m/sec (1ft/milli-sec).
Arranging speakers in an internal quad arrangement allows people to move in and out of the sound field as they wish. The most important benefit of quad systems is the ability to create exciting dynamic musical arrangements within a 3D three dimensional field.
Problem Venues
Long narrow reverberant venues are a curse. One must face defeat, not waste time and accept that no action of thought about placing a stereo sound system anywhere in the room will enable it to work. The simplest solution is a bulldozer, but the show must go on. The only thing that can be done is not to make the problem worse. Remember the golden rule intelligibility improves if sound comes from a single point source'.
The golden rule for problem venues. Intelligibility improves if sound comes from a single source. Also microphone feedback problems are reduced. It is only through habit that we place speaker systems on both sides of a stage. Avoid the use of wedge monitors in difficult environments. Another application where a single speaker stack is more effective is when a band is placed in a corner of a room. The speakers should be vertically stacked in an helix array. The bottom speaker is faced away from the band whereas the top speaker is faced across the band to act as cross monitoring.
I visited my old aunt in a small outback country town. It was their annual show. During the day was the competition for the blue ribbons for the best farm animals and local produce. Most exciting was the apple pie competition, which my aunt lost to a 16-year-old girl. At night were the sideshows, ferris wheels, and dodgem cars. The distorted noise from all the speakers brought tears to my eyes and transported me back to my childhood.
My first trip to a city was to a large department store. We crowded into a lift, where a little man sat on a stool controlling a leaver. There was silence except for the vomitus melody 'Never on Sunday'. My claustrophobic aunt trembled and held onto me. But to be trapped, unable to reach the speaker is what obsessed me. Later we went to a matinee 'Casablanca'. The projector whirred in the background, the sprocket slipped and the sound periodically went out of sync, but Bogey always had control.
Many years later at a rock festival, a group was smashing their guitars on stage and setting them alight. The lead singer was screaming into a microphone and the drummer was hacking at the speakers with an axe. A stoned (multiple set of keys) roadie mixed from the middle of the audience with a desk-light on himself, surrounded by groupies. The crowd went wild with excitement.
In each generation the rebelliousness of youth culture is symbolised by loud harsh distorted noise. I pray there must be a place in heaven where all these past experiences can remain intact and not need to be repeated.