Television, film, and 5.1
Despite the television and film industries both working to 5.1 formats, the underlying concepts are quite different. The top left photograph shows a small, stereo mixing room at Sodinor, in Vigo, Spain. This room, built to a Non-Environment concept, is used for the recording of voices, and also stereo mixing for television. The actors' lectern is visible at the far side of the room. A cardioid microphone facing the actor will not pick up the reflexions from the front wall because it faces the deep, rear-wall 'trap', yet the front-wall reflexions will greatly help the actors to have a sense of some acoustic life when they are working. (Voice-over actors do not usually use headphones.) Even for film, much dialogue is recorded in this way.
The Sodinor 5.1 mixing room is built to a generally similar overall concept to the stereo room, but is somewhat larger so that it can accommodate the 5.1 loudspeaker system. A priority of this room is still to function well for stereo mixes, because the bulk of the television work continues to be two-channel. This room can also accommodate a lectern for the recording of voices. However, there are still considerable regional and national preferences around the world as to whether it is better for the actors to be in the control rooms, or in separate studios. Many people feel that the work is quicker with the actor, script checker and recording engineer all in the same room. However, the Sodinor voice-over room provides another option for the clients in the same complex. Here, the actors can work in a room which has been optimised for the recording of 'clean' voices. The recording equipment is in an adjacent 'control booth'.
Soundub 14, in Barcelona, is a room that was designed for mixing in Dolby Digital 5.1, but it also had five loudspeakers behind the screen to accommodate mixing for the '7.1' Sony Dynamic Digital Sound (SDDS) format. This is not to be confused with the new, Dolby 7.1, which is a very different system, but it seems that various new cinema formats will soon be calling for five loudspeakers behind the screen in the fashion of SDDS, as shown. (The LFE loudspeaker drivers are McCauley 6174s. The principal loudspeakers are Reflexion Arts 234s.)
Somewhat in-between the above rooms is the Foley studio of Cinemar Films, seen at the bottom left. This is a room built to Dolby Digital specifications (although it is too small to be licenced to mix feature films), which is used for the pre-mixing of 'stems' and also for the recording of 'Foleys' (named after the first specialist in this line of work, Jack Foley, at Universal Films). When films are dubbed into other languages, the incidental sounds, such as footsteps, will be lost with the original dialogue tracks. In the photograph, with the Cinemar room still under construction, the different surfaces can be seen on the floor, including a container for water, so that the 'Foley' actors can synchronise new footsteps to the original picture, to be re-mixed into the new, foreign language soundtracks.
The frontal loudspeaker layout for a typical mixing (dubbing) theatre for film soundtracks is shown in the top-right photograph. The mono, '.1' (LFE) channel is fed through the two low-frequency loudspeakers, on the floor, which are asymmetrically mounted to reduce the build up of room modes at very low frequencies. There is also a photograph of the rear half of the room, showing the typical layout of surround loudspeakers, which can be switched between two, three or four channels, for 5.1, 6.1 and 7.1 soundtracks, respectively. The mid-frequency decay-time of the room is in the order of 200 milliseconds. The next photograph shows the same room during its fitting out phase, with all the acoustic work enclosed in fabric.
In so many of the studios where actors' voices are involved, the air quality must be maintained during the whole working day with a comfortable balance of temperature and humidity. This usually requires good ventilation, with the temperature being controlled in a way that does not dry the air - and hence the actors' voices. Shown at the right are the ventilation system components. The rectangular metal boxes contain the replaceable filter elements. The air then passes to the circular, in-line fans, and then through the green-painted water batteries before passing into the room via a suitable length of acoustic ducting, which acts as a silencer. Inside the room, the system produces no perceptible noise whatsoever. The thinner, black pipes, going to the water batteries are from the water pumps. The temperature of the water can be controlled, which, in conjunction with the rate of air flow can control the temperature of the room. Essentially, by using a high flow-rate for the water, and large heat exchangers, the water temperature need rarely be more than 10º different from the desired air temperature in the room, and so does not tend to dry the air as much as with the more typical, compact, heat controlling systems.