Studio monitors are loudspeakers in speaker enclosures specifically designed for professional audio production applications, such as recording studios, filmmaking, television studios, radio studios and project or home studios, where accurate audio reproduction is crucial. Among audio engineers, the term monitor implies that the speaker is designed to produce relatively flat (linear) phase and frequency responses. In other words, a studio monitor exhibits minimal emphasis or de-emphasis of sound frequencies. It's meant to provide an accurate reproduction of the tonal qualities of the source audio ("uncolored" and "transparent" are synonyms), with no relative phase shift of particular frequencies—meaning or distortion in sound-stage perspective for stereo recordings.
Beyond stereo sound-stage requirements, a linear phase response helps impulse response remain true to source without encountering "smearing". An unqualified reference to a monitor often refers to a near-field (compact or close-field) design. This is a speaker small enough to sit on a stand or desk in proximity to the listener, so that most of the sound that the listener hears is coming directly from the speaker, rather than reflecting off walls and ceilings (and thus picking up coloration and reverberation from the room). Monitor speakers may include more than one type of driver (e.g., a tweeter and a woofer) or, for monitoring low-frequency sounds, such as bass drum, additional subwoofer cabinets may be used.
There are studio monitors designed for mid-field or far-field use as well. These are larger monitors with approximately 12 inch or larger woofers, suited to the bigger studio environment. They extend the width of the sweet spot, allowing "accurate stereo imaging for multiple persons". They tend to be used in film scoring environments, where simulation of larger sized areas like theaters is important.
Also, studio monitors are made in a more physically robust manner than home hi-fi loudspeakers; whereas home hi-fi loudspeakers often only have to reproduce compressed commercial recordings, studio monitors have to cope with the high volumes and sudden sound bursts that may happen in the studio when playing back unmastered mixes.
Uses
Broadcasting and recording organisations employ audio engineers who use loudspeakers to assess the aesthetic merits of the programme and to tailor the balance by audio mixing and mastering to achieve the desired result. Loudspeakers are also required at various points in the audio processing chain to enable engineers to ensure that the programme is reasonably free from technical defects, such as audible distortion or background noise."The Development of High-Quality Monitoring Loudspeakers: A Review of Progress" (Expanded Version of I.EoE. Paper Read on 23 April 1958). Report No. L-041 (1958/31), The British Broadcasting Corporation
The engineer may mix programming that will sound pleasing on the widest range of playback systems used by regular listeners (i.e. high-end audio, low-quality radios in clock radios and "boom boxes", in club PA systems, in a car stereo or a home stereo). While some broadcasters like the BBC generally believe in using monitors of "the highest practicable standard of performance", some audio engineers argue that monitoring should be carried out with loudspeakers of mediocre technical quality to be representative of the regular systems end-users are likely to be listening with; or that some technical defects are apparent only with high-grade reproducing equipment and therefore can be ignored. However, as a public broadcaster dealing with a lot of live material, the BBC holds the view that studio monitors should be "as free as possible from avoidable defects". It is argued that real life low-grade sound systems are so different that it would be impossible to compensate for the characteristics of every type of system available; technical faults must not be apparent to even a minority of listeners while remaining undetected by the operating staff. It is further argued that, because of technical progress in the science of sound transmission, equipment in the studio originating the programme should have a higher standard of performance than the equipment employed in reproducing it, since the former has a longer life.
In fact, most professional audio production studios have several sets of monitors spanning the range of playback systems in the market. This may include a sampling of large, expensive speakers as may be used in movie theatres, hi-fi style speakers, car speakers, portable music systems, PC speakers and consumer-grade headphones.
Amplification: Studio monitors may be "active" (including one or more internal power amplifier(s)), or passive (requiring an external power amplifier). Active models are usually bi-amplified, which means that the input sound signal is divided into two parts by an active crossover for low and high frequency components. Both parts are amplified using separate low- and high-frequency amplifiers, and then the low-frequency part is routed to a woofer and the high-frequency part is routed to a tweeter or horn. Bi-amplification is done so that a cleaner overall sound reproduction can be obtained, since signals are easier to process before power amplification. Consumer loudspeakers may or may not have these various design goals.
History 1920s and 1930s In the early years of the recording industry in the 1920s and 1930s, studio monitors were used primarily to check for noise interference and obvious technical problems rather than for making artistic evaluations of the performance and recording. Musicians were recorded live and the producer judged the performance on this basis, relying on simple tried-and-true microphone techniques to ensure that it had been adequately captured; playback through monitors was used simply to check that no obvious technical flaws had spoiled the original recording.
As a result, early monitors tended to be basic loudspeaker cabinets. The state-of-the-art loudspeakers of the era were massive horn-loaded systems which were mostly used in cinemas. High-end loudspeaker design grew out of the demands of the motion picture industry and most of the early loudspeaker pioneers worked in Los Angeles where they attempted to solve the problems of cinema sound. Stereophonic sound was in its infancy, having been pioneered in Britain by an engineer who worked for EMI. Designing monitors for recording studios was not a major priority.
1940s and 1950s The first high-quality loudspeaker developed expressly as a studio monitor was the Altec Lansing Duplex 604 in 1944. This innovative driver has historically been regarded as growing out of the work of James Bullough Lansing who had previously supplied the drivers for the Shearer Horn in 1936, a speaker that had rapidly become the industry standard in motion-picture sound. He had also designed the smaller Iconic and this was widely employed at the time as a motion-picture studio monitor. The 604 was a relatively compact coaxial design and within a few years it became the industry standard in the United States, a position it maintained in its various incarnations (the 604 went through eleven model-changes) over the next 25 years. It was common in US studios throughout the 1950s and 60s and remained in continuous production until 1998.
In the UK, Tannoy introduced its own coaxial design, the Dual Concentric, and this assumed the same reference role in Europe as the Altec 604 held in the US. The British Broadcasting Corporation researchers conducted evaluations on as many speakers as they could obtain in around 1948, but found commercial loudspeaker makers had little to offer that met their requirements. The BBC needed speakers that worked well with program material within real professional and domestic settings environments, and not just fulfil technical measurements such as frequency-response, distortion, monitors in anechoic chambers. Above all, the BBC required monitors to sound balanced, be neutral in tone, and lack colouration.Seydor, Paul. "The BBC Monitor". The Absolute Sound's Illustrated History of High-End Audio p.306 Monitor usage in the industry was highly conservative, with almost monopolistic reliance on industry "standards", in spite of the sonic failings of these aging designs. The Altec 604 had a notoriously ragged frequency response but almost all U.S. studios continued to use it because virtually every producer and engineer knew its sound intimately and were practiced at listening through its sonic limitations.
Recording through unfamiliar monitors, no matter how technically advanced, was hazardous because engineers unfamiliar with their sonic signatures could make poor production decisions and it was financially unviable to give production staff expensive studio time to familiarize themselves with new monitors. As a result, pretty well every U.S. studio had a set of 604's and every European studio a Tannoy Dual Concentric or two. However, in 1959, at the height of its industry dominance, Altec made the mistake of replacing the 604 with the 605A Duplex, a design widely regarded as inferior to its predecessor. There was a backlash from some record companies and studios and this allowed Altec's competitor, JBL (a company originally started by 604 designer James B. Lansing), to make inroads into the pro monitor market.
Capitol Records replaced their Altecs with JBL D50 Monitors and a few years later their UK affiliate, EMI, also made the move to JBL's. Although Altec re-introduced the 604 as the "E" version Super Duplex in response to the criticism, they now had a major industry rival to contend with. Over the next decade most of the developments in studio monitor design originated from JBL.
As the public broadcaster in the UK, the BBC had the determinant role in defining industry standards. Its renowned research departments invested considerable resources in determining studio monitor suited to their different broadcasting needs, and also created their own models from first principles. A 1958 research paper identified the sound goal, in a monaural system:It is assumed that the ideal to be aimed at in the design of a sound reproducing system is realism, i.e. that the listener should be able to imagine himself to be in the presence of the original source of sound.
There is, of course, scope for legitimate experiment in the processing of the reproduced signals in an endeavour to improve on nature, however, realism, or as near an approach to it as may be possible, ought surely to be regarded as the normal condition and avoidable departures from this state, while justified upon occasion, should not be allowed to become a permanent feature of the system. In designing a loudspeaker, the BBC established the compromise that had to be established between size, weight and cost considerations. Two-way designs were preferred due to the inherently simpler crossover network, but were subject to the limitations of speaker driver technology at the time – there were few high-frequency units available at the time that functioned down to 1.5 kHz, meaning that the woofer must operate in a predictable manner up to about 2 kHz."The Design of the Studio Monitoring Loudspeakers Types LS5/5 and LS5/6". Report No. PH13 (1967/57), November 1967, The British Broadcasting Corporation The BBC developed a two-way studio monitor in 1959, the LS5/1, using a 58mm Celestion tweeter and 380mm Goodmans bass unit, but continually had problems with consistency of the bass units. The successful testing of a 305mm bass cone made with new thermoplastics led to development and deployment of the LS5/5 and LS5/6 monitors that occupied only 60% volume of its predecessor.