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Basic Microphone Technique

Article from Sound International, September 1978

Freelance engineer Steve Hall offers some guidance.


If you place a good musician alone in an acoustically treated room with a beautiful-sounding instrument and a top quality microphone, the job of sound engineering is made easy. But the normal recording situation is far less perfect than this; it is this imperfection that demands an engineer with experience, received technique and, if nothing else, a good few tricks up the sleeve.

Microphones to the sound engineer are like lenses to the photographer; good pictures can be taken with a relatively cheap camera, and without the need for controlled lighting and expensive auxiliary equipment — as long as the lens is good and the photographer careful to arrange the shots. Similarly, good recordings can be made with relatively cheap tape machines, and without the need for fully-controlled acoustics and a studio full of electronic aids, as long as the microphones are good and are carefully placed. Yet many small studios seem to overlook these vital pieces of equipment as they hurry to jump into more tracks and bigger mixers. Ultimately a studio will gain its reputation on the strength of an excellent drum sound, or a cool clear vocal sound — not on the sheer number of tracks crammed on to ¼in tape.

The first problem encountered in a small studio when positioning mics is 'spill'. As soon as you get more than one mic and more than one musician in the same recording area, there will always be some degree of unwanted noise crossing between mics; some musicians can work in the sort of isolated conditions that will minimise this spill, but others will need the natural reinforcement and subtle cues from their fellow musicians that can only be achieved by playing 'for real'.

It follows then that in the quest for separation between musical sounds, the engineer will be treading a fine line between over-isolating a musician to the detriment of the performance, or over-indulging the musician to the detriment of the recorded sound. If an engineer feels that a particular sound may be improved by placing the musician in an unnatural playing position, it is up to him or her to advise but not dictate; a relaxed and natural performance will always score over the cleaner yet more mechanical one.

Many musical instruments rely on subtle and high harmonics to give flavour and brightness to the notes they produce; as a rule, acoustic instruments rely most heavily on their harmonics, so it is these instruments that require microphones with a particularly good frequency response. Of the three microphones in common use — the condenser, dynamic and ribbon mic — the condenser mic most easily handles the wide frequency response demanded by acoustic instruments; however this kind of mic does have some disadvantages: 1 It requires a power supply, 2 it can be damaged by high sound levels, 3 it can sometimes be cumbersome in size, 4 close vocal work can make it 'pop' easily, and 5 breath condensation can cause it to produce stomach-like whines and gurgles.

Dynamic mics, with their contrastingly lower output and resilient construction, are indispensable for high sound-level applications such as electric guitar amplifiers, bass drum, and bass guitar. Since much modern music demands a close-mic technique, it is this that I will be primarily considering in this article.

I would like to describe a recording which illustrates the unpredictable nature of microphone positioning: I was engineering the final touches to an LP for an American folk singer which, among other things, included sticking a tambourine on to one of the tracks; it was a particularly nice-sounding tambourine and when the artist came into the control room to hear playback, he noted that something was missing from the sound he knew so well. Since I had recorded it using one of my best mics and at a distance of about 2ft, I told him not to worry and that I could always equalise it to his specification at mixdown. He was not so sure about this 'equalising', and asked for a demonstration before we moved on to the next overdub; I demonstrated a whole variety of textures from this one take of the tambourine, yet he was not impressed — it was not the sound his ears were hearing. So with the bit between my teeth I began jumping from studio to control room, while he played continuous unaccompanied tambourine, adjusting distances, angles and location of various mics in order to produce this precious sound that he was after. Eventually I found just the right combination: he had to stand facing a corner of bare walls with an omnidirectional mic hung high over his head. Clearly the reflected sounds were playing an important part in the overall, and indeed very pleasing, sound. Although this kind of experimentation is essential to the art of recording, time, unfortunately, seldom permits this fascinating method of discovery. Nevertheless it is important to remember that the straightforward way of placing a microphone may not always be the most effective way.

Drums



The snare drum is one of the most difficult instruments to record, yet it plays a vital part in a successful backtrack; when close-miked it tends to produce a rather lifeless sound, yet to prevent it being lost in a full musical production it needs to have a fresh crisp edge. Some engineers like to use the AKG 202 or 224 dynamic mic because it is highly directional and gives a hard edge to the sound; I prefer the warmer sound of a condenser mic — I use a relatively cheap Calrec 600 — and add about 10dB of 9KHz and 5dB of 100Hz to give the snare a more substantial bottom end and a smooth top end. I find that the low frequencies help the snare to poke through a particularly complicated mix.

Try aiming a directional mic at the top rim of the snare drum and a couple of inches above so that it can equally 'see' the skin and down the side of the shell — this position will pick up both the attractive sound of the snare-wires and the full force of stick on the skin. You will notice that as the high frequency boost is applied to the snare, the hi-hat is also brought into the picture; this removes the need for a separate hi-hat mic, and can be controlled somewhat by the degree of boost applied. If the hi-hat is too loud as a result of adding enough 'boost' to achieve a lively snare sound, the problem belongs with the drummer — a good session drummer will be very light on the hi-hat and firm on the snare.

For the rest of the kit, directional dynamic mics are quite suitable; use your better quality ones for the cymbals. Point your mics at the centre of the tom tom skins from just over the edge of the rims and an inch or two above. The cymbals can be miked up at a greater distance — about 8in over and to the rear to avoid flying sticks and lashing cymbals. A mic placed too close will pick up unwanted mechanical hums from this large area of metal. For bass drum, most engineers prefer the AKG D12 — I use the D25, an older version of this mic. A bass drum puts out very high sound pressures, and this dynamic mic can not only handle these, but also avoids overloading the mixer, thanks to its low output; however, there are many different makes of dynamic mic that would be equally as suitable if only given a try.

Having positioned your mics carefully around the kit you will find that much of the sound quality now depends on the tuning, damping, condition and quality of skins. And finally, remember when you are struggling with the position of mics, faders and amount of eq to rectify a rather lifeless drum sound: it takes a good drummer to produce a balanced and solid sound.

If you are short of mics, a drum kit may be recorded to good effect using only two or three mics — one on the bass drum and a stereo pair above the kit; a fourth one on the snare is helpful. A closer sound can be achieved by placing the mics down between the toms and cymbals.

Congas can be miked up as for tom toms, but when working with only one mic on a pair of drums, as with bongos, it should be placed slightly closer to the lower skin in order to achieve an equal balance.

Vocals



The most severe quality test on a microphone is the human voice; it therefore follows that your vocal mic should be chosen with great care. My favourite is the Neumann U47, one that has been around for some 30 years. It is a condenser mic and so handles well the complicated pattern of harmonics and overtones found in the human voice. It also has two other characteristics that make it especially good for vocal work. It has a large valve inside and so warms up to a friendly working temperature — which in turn prevents moisture from a close vocal forming on the rather sensitive microphone head. The U47 also has a polarity switch to change the field of pick-up from unidirectional to omni-directional: in this second position close vocal work can be carried out without the need of a pop-shield (I find that a shield can degrade the vocal sound). I quite like the AKG C414 mic for backing vocals since its slightly exaggerated frequency response contributes well to the nice bright edge necessary for this kind of work.

When recording vocal tracks there are certain rather tricky problems to overcome. Well-disciplined singers will produce only small fluctuations on your record meter between their highest and lowest notes, yet a more modestly gifted singer may hardly make the needle flicker on low notes but send the needles straight into the red without warning on the highs. Since many singers are treading a delicate path between either catching the right take or losing it completely, it is the engineer's responsibility to catch every serious take come what may — regardless of any great inconsistencies of levels; the engineer must be poised ready to 'parry' a singer's sudden loud bursts, yet be ready to push the fader back up for quiet passages — an old technique known as 'riding the level'. Of course that marvellous piece of electronics the compressor/limiter will handle this task; but where there are large changes of level, the limiter will noticeably degrade the vocal sound. A small amount of compression can be helpful to iron out small inconsistencies, but the large ones should be handled by riding the level on the mixer and by the vocalist moving into the mic to compensate for soft notes. Thus an otherwise unusable vocal sound can finish up as a smooth, clear and easily-mixable track.

This leads me to a general point. Many engineers preach the religion of recording all sound on to their master tape without using any equalisation — known as 'recording flat'. This, they claim, leaves open the most options for equalisation at the final mixing stage. Other engineers preach the opposite and suggest that a producer with a clear and confident vision of the final product will be committed to finished sounds on each instrument as it is recorded.

In a small studio, I prefer working with the second method for two reasons: firstly, I believe it is easier to measure the effect of each successive overdub on a backing-track if the quality and texture of this track substantially resembles the finished article; secondly, where 2-, 4- or 8-track recordings rely heavily on the use of sound-on-sound, track bouncing or submixing to extend track facilities, and where there is no noise reduction, it is essential to record on to the master with the full amount of eq that will be needed on mixdown. Also, without the use of a high quality noise reduction system, if a track requires heavy high-frequency boost off-tape, hiss will also be boosted. For this reason alone it is advisable to apply any eq necessary at the recording stage of a session.

There is another important consideration to take into account at this stage of a session. Be sure that as many of the inconsistencies of level and quality are ironed out as and when they occur; the final mixdown stage of a session is a very creative part of the finished product and so should not be cluttered up with rectifying mistakes or compensating for changes in level or equalisation.

Strings



An exciting cello sound can be achieved by placing a mic below the bridge near the left-hand 'f' hole; and again, as the mic is moved back, the less fruity and more natural the sound. But beware cellists who insist that the best sound can be produced by their contact pickup. As a rule most acoustic instruments are far more rich and have more interesting overtones than a pickup will handle. For special effects, or for live work, the acoustic and magnetic pickups are essentials, however.

Violins can be miked up to good effect from above at a distance of about 3ft. A rather thin 'tizzy' effect will result if this instrument is too closely miked.

And now for a general word of warning: if you are placing microphones around an instrument in preparation for a stereo recording, give a quick listen to it in mono before committing it to tape; multi-miking can cause serious 'phase' problems if mics are positioned close together and out of parallel with each other — these problems are most noticeable in mono, where a loss of bass or a mushy treble may be observed.


Acoustic Piano



The acoustic piano can pose many problems for the engineer; most standard upright and grand pianos are at a great disadvantage in the recording studio since for a piano to record well it needs to produce certain high overtones, known in the piano trade as 'breath', that contribute greatly to the bright edge so often associated with good German pianos. Some studios try to create this edge by doping the hammers, but this is ruinous to a good piano and produces more of a honky-tonk sound. However, the use of heavy treble eq can go some way to achieving an attractive sound. You will need to use your best mics on this instrument since it tends to be rather sparing with the high frequencies it puts out.

Try placing directional mics in the more obvious places — near the treble hammers, near the bass bridge, where the strings cross over the frame holes; you will find with experimentation the best spot to place one, two or three mics simultaneously in order to produce a mono or stereo effect. And, like the acoustic guitar, the distance away from the sound board of the piano will dictate the degree of 'naturalness' of the sound. To achieve a hard, cutting sound, try cutting the eq sharply around 400Hz and boosting around 9KHz. Be aware, though, that while you are heavily boosting high frequencies on the piano, you will also be exaggerating the pick-up of other local high frequency sounds, such as the click of a plectrum or the whisper of a guide vocalist — or even unwanted instruments leaking from a pianist's earphones. And if you have any distortion in any of your equipment that normally stays hidden, you can be sure that it will show when recording a piano; this instrument can have a very transparent sound and will reveal most of the problems and shortcomings of a studio system.

Brass



When recording brass instruments, don't just stick a mic up towards the flare of the horn. Many of the more interesting harmonics emanate from the keying area and the mouthpiece so, when close-miking, try to find a mid point between the flare and the keys.

Acoustic guitar



The acoustic guitar can produce a recorded sound that can vary from small and mellow to large and rich with exciting overtones and colouration. When using an acoustic guitar to augment a reasonably full production, the sound should not contain too much of the colourations that can sound so attractive in solo recordings; these overtones can cloud over a carefully-placed hi-hat or delicate percussion, and the low colourations can quickly muddy-up the bass guitar or the left-hand of a piano. For solo or heavily acoustic tracks, a condenser mic will flatter an acoustic guitar; for overdubbing on to a track full of other instruments, a dynamic mic is sometimes preferable since it tends to extract a more usable middle sound from the guitar.

For a mono recording use a directional mic and place it quite close to the sound-hole, pointing in towards the end-pin. This angling of the mic reduces the boominess associated with close-miking an acoustic guitar. For a stereo effect place two mics parallel to each other directly facing the guitar at a distance of about 1ft — the closer the mics are to the instrument and the wider they are apart, the greater the stereo effect — the further away they are the more natural the sound. A rather sensational stereo effect can be produced by placing one mic as for 'mono', and another mic directly facing it but behind the guitar; the rear mic will need to be quite a sensitive one since the guitar is rather quiet at the back — the closer this mic can get the better.

Electric Instruments



There are two main methods of recording an electric instrument. The first way is to plug it straight into the mixer or tape machine by using a special matching and isolating transformer (Direct Injection); the second way is to plug the instrument into its respective amplifier and place a mic in front of it. It is more a matter of taste, convenience and fashion as to the exact way in which these instruments are recorded.

Electric guitar: some of the raunchiest and heaviest sounds can be achieved by using quite a small studio amplifier, however some amps used in the studio can be very powerful. A dynamic mic will happily cope with this. My favourite mic for electric guitar is a Beyer M260 ribbon mic which has the characteristic of boosting the low-mid frequencies at close range; this can be very helpful to thicken up the sound of thin strings played high. If the studio set-up permits, a second distant ambient mic can be positioned for a guitar amp and mixed into the final mono or stereo picture to add a live quality to the performance. Electric guitars can sometimes be DI'd to obtain a glassy sound that can be attractive for certain rhythm work.

Electric bass can be recorded in the same way as guitar, but is more often than not DI'd to achieve a pure and smooth bottom end; sometimes the bass is simultaneously plugged into an amp and the two sounds mixed together to finish up with a combination of the purer tone and the harder texture that the amp and DI can give. It may seem a contradiction, but some of the best bass sounds are achieved by recording with much of the lower bass frequencies removed.

Electric keyboards are often DI'd to catch some of the interesting high harmonic distortion that accompanies many of the better known electric pianos. Synthesisers are happiest DI'd since clearly some of the very high textures found in this instrument would be lost through many a stage amp. Where a live feel is important, playing electric instruments through their stage amps turned up loud is the only way to record — microphone spill and all.

As already mentioned, and with particular regard to electric instruments, the name of the game is experimentation. The way in which we hear and understand musical sound is an inexact science — consequently there are no hard and fast rules concerning microphone positioning. It can sometimes be a matter of trial-and-error and ultimately just believing your own ears. However, an engineer is often working against the clock with the musicians, so it is essential that there should be a repetoire of 'safe' techniques and mic positions to cope with the more commonly-found recording situations.


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Publisher: Sound International - Link House Publications

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Sound International - Sep 1978

Donated & scanned by: Mike Gorman

Feature by Steve Hall

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