Microphone Guide - Mic Technique
Microphone Guide - Mic Technique From sE Electronics
VocalsVocal recording is often considered difficult but it is actually pretty straightforward as long as the acoustic environment is taken into consideration. For most studio work, a relatively dead environment is ideal as it allows artificial reverb to be added while mixing. Small vocal booths may give the illusion of sounding dead, but unless very well designed, may actually sound quite boxy due to a lack of low frequency absorption. A better approach may be to place the singer in a larger room and then apply localised acoustic treatment. A combination that works well is to place acoustic absorbing gobos behind and to the sides of the singer and an sE Reflexion Filter TM behind the microphone. In low rooms, an absorber placed above the singer’s head also brings about significant benefits and in smaller rooms, avoid placing the singer or microphone close to either the walls or the exact centre of the room.
A metal mesh pop screen will usually produce less in the way of tonal artifacts than a fabric screen and few singers can manage a pop-free performance without one. Place this around 50 to 75mm from the microphone with the singer’s mouth typically 150 to 250mm from the microphone. The microphone height can be adjusted so that the singer sings slightly above or below the axis of the microphone if this produces a more suitable tonality. The microphones own low cut filter may be engaged if necessary to further reduce popping and low frequency spill, although always check that this doesn’t compromise the natural sound of the voice.
The choice of microphone is entirely a function of what suits a particular singer, and the most expensive model won’t necessarily sound the best. While large diaphragm, cardioid capacitor microphones are the most common choice for studio vocals, different models sound either bright, or warm so it is necessary to match the characteristics of the microphone to the strengths and weaknesses of the singer. You may also find that a small diaphragm model sounds more natural in some cases, and if you’re after a more rounded, vintage sound, try a ribbon model. The extended high end response of the sE RNR1 ribbon microphone makes it suitable for both vintage and contemporary sounding vocals.
Acoustic GuitarAcoustic guitars, both steel and nylon strung, can be fairly quiet instruments if picked rather than strummed, so a fairly sensitive microphone with low self noise is desirable. Condenser microphones are often used as they are easily able to capture the high frequency detail of these instruments and for the most natural sound, a model with a nominally flat frequency response may be desirable. However, a microphone with a specific character can be chosen if it suits a particular instrument so the end always justifies the means. At the outset, it must be emphasised that the microphone will pick up both the direct sound from the instrument itself and sound reflections from the environment in which it is played, so some acoustic screening may be needed to control the amount of reflected sound reaching the microphone.
Most acoustic instruments, the guitar included, sound best if played in a sympathetic room where the reflected sound supports the natural tonality of the instrument. Covering the floor beneath the layer with hardboard or other reflective material if the room is normally carpeted can create a localised live environment. It may also help to play close to a reflective plaster or wood panel wall. The key to a good guitar sound is to find the best position for whichever microphone you choose to use. Great results can be achieved using large diaphragm models, small diaphragm models, cardioids and omnis. Omnis can give a very sweet sound but you may need to screen off the rear and sides of the mic if spill from other parts of the room becomes a problem. If you are fortunate enough to own an sE RNR1 ribbon microphone, you will find that this also sounds extremely good used on acoustic guitars, when ribbon microphones from other manufacturers may sound too dull in this application.
The easiest way to find the best mic position is to monitor the mic output via good quality headphones and then move the mic around the guitar as the player runs through the piece. Many engineers start out aiming at where the neck joins the body from a distance of around 350mm but you can also get results by setting up the mic 150mm or so in front of the guitar and then aiming it at the guitar bridge either from above or below the guitar. Again a mic distance of around 350mm is a good starting point but you’ll need to experiment to find the ‘sweet spot’ as every combination of player, room and instrument is different. In cases where the player moves excessively, consider using a guitar body mounting arrangement for the microphone such as the sE GM10 system which comprises an effective clamp and adjustable arm with a small high quality condenser microphone attached. Recording the guitar using a single mic avoids any mono-compatibility phase issues that might occur with spaced stereo mics, but a guitar part can be given more width and definition by mic’ing up the body as just described and then aiming another mic part way up the neck. The outputs from the two mics can then be panned apart slightly in the mix. Unless the guitar is physically small and bass-light, avoid pointing a microphone directly at the sound hole as this tends to capture a very boxy, resonant sound.
Electric GuitarThere are probably as many ways to mic up the electric guitar amplifier as there are engineers but some standard approaches have evolved. Because of the restricted frequency response of guitar speaker systems, which don’t employ tweeters, dynamic microphones have a more than adequate frequency range and can tolerate the high SPLs that occur close to the grille cloth. A general purpose cardioid or omni mic will usually give quite adequate results and now that ribbon mics are becoming more affordable, these are once again becoming popular for recording the electric guitar. Some engineers also prefer the sound of condenser microphones, usually large diaphragm models, so there’s no hard and fast rule as to which type of microphone to try. Cardioid mics don’t pick up sound from the rear as omnis and ribbon (figure-of-eight) mics do, but if they’re placed very close to the speaker grille, spill from other souces is unlikely to constitute a serious problem.
When using a single mic, a position close to the grille cloth is the normal starting point but it is important to try different positions across the face of the speaker as you get a different tone when mic’ing the centre as you do when mic’ing close to the edge. At the SPLs guitar amps generate, microphone sensitivity and noise are unlikely to cause problems — the most important thing ‘spec-wise’ is to choose a mic that can handle a high SPL without clipping. Try all the mics you can as the most obvious choices may not always produce the best results. While the single mic approach can produce great results, it is not uncommon to see engineers putting up both ribbon and dynamic mics close to the speaker grille, and where the room has a sympathetic ambience, a condenser mic a couple of metres back. The outputs from the various mics can then be combined and mixed to give the desired sound. If the guitar is played in the control room with the amp in the live room, it is also possible to mic the guitar strings directly using a capacitor mic and then mix a little of that in with the mic’ed amp sound to add definition.
Drums and PercussionDepending on the kit, how well it is tuned and how well it is played, drums can either be a joy to work with or the source of much frustration. A good sound starts with a good sounding kit, and though that sounds obvious, there are many examples of engineers trying to fix the sound of a bad sounding kit using EQ and compression. A good-sounding kit will have the correct heads fitted for the type of music and will be well maintained to avoid squeaks and rattles. Good tuning and correct damping is paramount. Drums often sound best in a slightly live environment, but in the smaller studio you may be better off trying to exclude wall and ceiling reflections and then add ambience when you mix using a suitable reverb device or plug-in.
Top-league studios have large drum rooms with high ceilings, so in the smaller studio, getting rid of ceiling reflections that might otherwise leak into the overheads is a priority. You could stick acoustic foam to the ceiling but a less permanent solution is to use sE Instrument Reflexion Filters TM on the drum overheads. Acoustic foam panels may be hung on the walls to control excessive small room liveness but don’t be tempted to use carpet as that will only make the room sound more boxy. The close drum mics are less of a problem as they pick up relatively little room sound.
Kick drums are easier to mic in the context of rock and pop music if they either have the front head removed, or are fitted with a front head into which a hole has been cut to allow some flexibility in positioning the kick mic inside the drum shell. A wooden or plastic bass drum beater gives a harder, more defined sound than softer beaters and it is usual to damp the kick drum using a folded blanket placed inside the shell so as to prevent the batter head from ringing too long. The snare drum may be damped using duct-tape or materials such as Moon Gel but damping is not normally applied to the lower snare head as this prevents the snares from vibrating properly. The same approach can be taken with the toms, which may either be double or single headed.
Drum Mic’ing OptionsFor some styles of music, such as jazz, the entire kit can be recorded using just one or two microphones set up between one and 1.5 metres from the ground and placed a couple of metres in front of the kit. These will capture the live sound (and stereo imaging if a spaced pair is used) of the kit as it sounds in the room, but for this to work well the room has to augment the sound of the kit rather than simply muddy it. While condenser mics are the usual choice for room mics, a high quality ribbon mic (or stereo pair) such as the sE RNR1 placed a couple of metres in front of the kit can sound wonderful in a good room. Even with this purist approach, the snare and kick drums often benefit from having their own close mics that can be mixed in to give them more definition. With such a setup, the two front mics may be moved to above the kit so as to better capture the sound from the cymbals and toms, though in good sounding rooms, the use of both room mics and overheads often yields the best results.
Some engineers are very careful to ensure the two mics are the same distance from the snare drum so as to avoid “comb filtering” effects should the track be played back in mono. Snare mics are often simple dynamic models whereas the kick mic could be a large diaphragm condenser mic or a specialist dynamic model with an extended bass response. As long as you choose a model with a high SPL handling capability, you won’t damage anything while experimenting. A typical snare mic position would be 50mm above the rim and aimed towards the centre of the drum head, while the kick mic is often placed just inside the drum shell aimed somewhere between the beater and the drum shell. Every kit is different so some experimentation is invariable necessary to get the best result. A more sophisticated approach would be to set up a second large diaphragm condenser mic a metre or so in front of the kick drum, and then balance that with the mic inside the shell.
Overheads may be set up as a coincident pair or spaced at around two metres from the floor. A coincident pair would normally be based on two cardioid condenser mics with their capsules close together and their axis pointed to either side of the drum kit but where spaced mics are used, any of the main pickup patterns can be used. Many professional engineers also like the sound of ribbon mics as overheads as they give a smoother, more rounded sound to the cymbals. Whatever mic type or pattern is used, in low rooms, some form of acoustic absorber between the mic and ceiling is desirable.
Tom mics are set up similarly to the snare mic, and may be either dynamic or capacitor models. Both snare and tom mics should be positioned so they point away from adjacent drums (and hi-hats) where possible so as to minimise spill. In pop music recording, drums are invariably mic’ed individually as well as by means of overheads and perhaps more distant room mics.
Typically the overheads and room mics establish the essential character of the sound, then the close mics are brought in to add focus and to fine-tune the balance. Separate hi-hat mics can be used where the overheads aren’t giving them enough prominence and are generally condenser models. Positioning the hi-hat mic 200 mm or so from the side of the hi-hat cymbals, either just above or just below the cymbals, ensures it doesn’t get hit by a blast of air every time the hi-hats are closed. Other percussion such as congas, djembes and so on may be mic’ed from overhead in either mono or stereo using capacitor microphones. The further the mic is raised above the drum, the more room ambience will be captured along with the direct sound. As with the drum kit, a naturally live environment often produces the most pleasing sound.