Music Technology Handouts: Sound balancing: 2

Sound balancing: 2

When you have studied this section of Music Technology Handouts you should know about..

good recording acoustics
good stage layout
good control room location
recording chamber music
recording early music
recording woodwind
recording solo instruments
recording a singer with piano

Introduction

The coincident pair system and the space microphone system can both be applied to recording ensembles that are internally balanced.

Recording "classical" music: General points

The fundamental requirement is a good acoustic, that is one which is free from noise and which has suitable reverberation. A typical reverberation time is 1.5 to 2.5 seconds. There should be an even decay of all frequencies, (although a slight increase in the decay time of lower frequencies is acceptable).

The second requirement for a satisfactory recording session is a good layout of the performers so that clarity and separation of the parts can be achieved. If the orchestra or choir is large it helps to have some sort of staging, terracing or even a balcony to assist in separating the sections.

Thirdly, a suitable room is required for use as a control room. Sometimes a double or triple glazed room looks out on the auditorium but often there will be no visual contact between the hall and the control room. A closed circuit television, (C.C.T.V.) can be helpful or an audio assistant may be equipped with talkback and stationed in the hall.

Often the control room is set up in a dressing room, a greenroom or even a corner of a corridor. The acoustic may be brighter than is ideal but can be improved with heavy curtains and blankets. Like the hall itself, the control room should be free of ambient noise, e.g. traffic sounds. Otherwise it is impossible to tell whether noise is being picked up by the mics. in the hall or heard directly in the control room. The sound engineer will have to make a mental adjustment to the listening conditions in the improvised control room. This adjustment may be assisted by listening to a familiar pre-recorded tape. Try to choose a room with good, level access; you will have much equipment to carry in. The building layout will probably be unfamiliar so make sure you can find your way out quickly in case of fire. Remember, visibility may be zero.

Having located a suitable hall and having chosen a room for use as a control room; the next requirement is to choose the microphones. This is largely a matter of personal choice, (and a matter of what is available). Capacitor, (condenser) mics. give a quieter sound.

Recording: Chamber music, (e.g. string quartet)

This sort of music is relatively quiet therefore a low level of ambient noise is essential. If the hall is too reverberent, a harsh tone may result. Churches are often unsuitable for this reason. Wood panelling seems to help produce the type of warm tone that is required. Some situations result in so-called "wolf" notes, i.e. notes that sound particularly loud. These result from room resonances and it may be necessary to reposition a musician or use acoustic screens to overcome this problem. Individual mics. are not required as the enemble is internally balanced. A cluster of 3 omnidirectional mics. placed in front of the musicians and about 3 metres high would be a likely starting arrangement. The artistes may need to be spaced out more than usual to give clear stereo positioning.

Diagram

For chamber music that includes a piano, (e.g. a piano quintet) the other instruments can be placed on the "dead side" of the piano. This reduces the amount of sound from the piano that is picked up by the mics. covering the other instruments, i.e. "spillage" is reduced.

Diagram

Recording: Early music instruments

These are instruments of ancient origin and tend to lack "volume". When early music instruments are played in a group the internal balance tends to be rather poor. The balance can generally be improved in the mixing process. Since the instruments are rather quiet the music tends to be of a quiet, intimate nature. Little reverberation is therefore required. An overall stereo image can be formed with a trio of omnidirectional, ("omni") mics. Spot mics can be added for individual instruments. Some instruments are so quiet that much gain is required in the mic. channel. This can exaggerate instrument (and player) noises. If the instrument has a limited frequency range, this can be turned to advantage and filtering can be used to reduce the extraneous noises. Each instrument should be listened to, through the mixer, to determine what adjustments are necessary. Sometimes a player can help by modifying his or her playing technique.

Recording: Woodwind ensembles

Spaced mics. or a coincident pair may be used for the overall stereo effect. Spot mics. for wind instruments are placed lower than for strings. The sound from clarinets and oboes comes from the flared end of the instruments so their mics. need to be fairly low and angled upwards. The bassoon directs sound upwards and to the (audience) left; so its mic. can be angled downwards. All these instruments produce a good level of sound and do not require close mic. placement. Some mics. can produce a harsh, nasal tone especially with the clarinet. This may be desired in some kinds of music but not with "classical" ensembles. A mellow sound may be achieved by using a ribbon mic. Some dynamic mics. give a mellow tone but most have a peak in the mid-frequency region that makes the sound over-bright. The sound of the side-blown flute is projected horizontally at the height of the hole in the head of the instrument.

Recorders are quieter than orchestral woodwind and mics. should be placed closer.

Recording: Solo instruments

With solo players there is no difficulty with sound spilling over from adjacent instruments, so there are fewer restrictions on placement or types of mics. used. A coincident pair or spaced mics. are equally suitable. If omnidirectional spaced mics. are used there is no need to angle them outwards; they can be mounted about 20 cm apart facing the same direction. The source of the sound should be on the axes of the mics. Directional mics. are only necessary in difficult acoustic conditions. The hall or studio acoustic should be chosen to suit the type of performance, e.g. a small, less reverberent hall for a harpsichord; a larger, reverberent hall for a romantic piano recital. The classical guitar can be difficult to record because the mics. need to be close to the instrument where finger noises, particularly "whistles" on the lower, wound strings become obtrusive. A warm sounding mic. is essential. It may need to be positioned to the side or even over the shoulder of the player.
The piano can also be difficult to record well.

Mic. positions can depend on:

the instrument
the acoustic
the player
the music being performed.

Diagram

Recording: Singing with piano accompaniment

The coincident pair and spot mic. combination is useful for operatic type solos. For more intimate music a spaced pair may be used, similar to the arrangement used with the piano quintet.

Diagram

The actual position of the vocal mic. will depend on the relative levels of the voice and piano. This arrangement can be used in a studio recording but would not be suitable for a public recital. For public performance it is necessary to position the singer to the (audience) right of the piano and use directional mics. to achieve separation.

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