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These evaluations must be of the recording itself, not of the recording through the monitor system, if the recordist is to be in control of the recording process, and if the recording is to have the same sound relationships in another (neutral) listening environment.
The most desirable monitoring system is transparent; the loudspeakers reproduce the sound in the control room without distorting the sound quality. This seems to be almost an impossibility. Many complexities are present in the selection of an approach to monitoring. The immediate considerations for the monitoring process itself are:
• Loudspeaker and control room interaction
• Effective listening zone
• Sound field: near field versus room monitoring
• Monitoring levels
• Stereo/mono compatibility
The control room itself will distort the sound emanating from the loudspeakers. The acoustics of the control room can cause radical changes in the frequency response and time information of the sound. Ideally, any listening room would have a constant acoustical absorption over the operating range of the loudspeakers, and would appropriately diffuse the sound from the loudspeakers to create a desirable blend of direct and reflected sound at the mixing/listening position.
Non-parallel walls; non-parallel floor and ceiling; acoustical treatments to absorb, reflect and diffuse sound where needed; careful selection, placement and installation of loudspeakers; and a sufficient volume (dimensions of the room) will minimize the influence of the control room on the sound coming from the loudspeakers.
The room should absorb and reflect all frequencies equally well, should produce very short decay times that are at substantially lower levels than the direct sound from the loudspeakers. The room should not produce resonance frequencies, and should not produce reflections that arrive at the listening position at a similar amplitude as, or within a small time-window (2 - 5 ms) of, the direct sound.
As needed, rooms may be tuned for uniform amplitudes of all frequencies by room equalizers, and tuned for the control of reflections (time) with diffusers, traps, and sound absorption materials. The ideal control room has been designed to include very specific acoustical treatments, and in such a way that room equalization is not needed.
Designers of recording studios have widely divergent opinions on the most desirable acoustical properties of control rooms. Conflicting information and opinions are common. The objective of all designers is very similar, however: it is to produce a listening environment that is most suitable for the listening of reproduced sound.
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Figure 5-2. Loudspeakers as Part of the Control Room, and the Effective Listening Zone. (click on image for full size)
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Loudspeaker placement is part of the design of control rooms. Ideally, the loudspeaker should be a part of the wall, mounted within the wall itself so the front of the loudspeaker is flush with the face of the wall. This negates the usual boost of low frequencies that results when a loudspeaker is placed near walls, ceiling, and floors (and especially in corners). Placement away from side walls by four feet and from the front wall by about three feet will minimize the boost of low frequencies, that occurs when the omni-directional low frequencies reflect off the wall surfaces, and combine with the direct sound from the speaker.
The loudspeakers should be aligned on the same vertical plane, usually at ear-height for a seated person, or slightly higher. It is important that the meter bridge of the console not be in the path between the loudspeakers and the mix position, and that strong reflections off the console are minimized. The loudspeakers should be aligned symmetrically with the side walls.
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The effective listening zone is that area where the sound is accurately perceived, as it is reproduced through the two loudspeakers interacting with the control room. In a control room, the mix position and/or the producer's seat are located in the effective listening zone. The size of the effective listening zone is usually quite small in most control rooms; it is an area that is equidistant from the two loudspeakers, is roughly the same distance from each speaker as the speakers are from each other, and few strong reflections arrive at this area. Angling of the loudspeakers (60° to 90° with respect to each other) towards the listening zone increases the size of the effective listening zone, given complementary room acoustics.
For accurate spatial perception, it is vital that the effective listening zone be carefully evaluated. The listener must be located almost exactly between the two loudspeakers (depending on the acoustics of the control room), and the volume level must be the same at each speaker when identical signals are applied to each channel. The control room should be virtually transparent in the listening zone.
The effective listening zone of the control room is in relation to the studio monitor speakers. This is the monitoring system that provides the most accurate information of the qualities of the recording being made. The studio-quality loudspeakers are of high quality and are carefully engineered. They are designed to provide non-distorted, detailed sound, while working within the acoustic characteristics of the control room.
Most people who purchase the recording will have playback (monitoring) systems of somewhat (to significantly) less quality than the recording studio. The sound of the recording in the audience's listening environment (the individual's home, automobile, etc.) will be different from that of the recording control room. It is common for recordists to use several sets of monitor speakers to obtain an idea of how their project will sound over home-quality playback systems.
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