If you don't have a multitrack but you're keen to start experimenting with recording, good results can be achieved with just a couple of mics and a domestic cassette deck. Paul White shows you how to be a stereo MC...
I must have been about ten years old when I first started experimenting with tape recording, and in those pre‑cassette days, all that you could get your hands on were clumsy open‑reel machines that recorded in mono only, and had the bandwidth of a dictaphone. Trying to get around the limitations of the equipment was a constant challenge, whereas today you can buy a hi‑fi cassette deck with mic inputs for less than £100, and use it to make surprisingly professional‑sounding recordings.
The first thing to realise about music recording is that it is very similar to photography — you can only photograph what is there, but the end result varies enormously depending on camera angles, lighting and choice of lenses. It's the same with recording music: the raw material is the musical performance, but you can capture that performance in different ways, depending on the type of microphones you use, where you position them, and the type of acoustic environment in which you choose to record.
In the early days of recording, everything was mixed down to mono in one take, but these days we've got used to stereo, where two different signals are recorded, then played back over two loudspeakers to approximate the original event. At its simplest, this means using just two microphones. This may sound limiting, but it's actually a very accurate way to record acoustic performances, and many of the best classical recordings are made this way.
The downside is pretty obvious too — the performers have to get the whole song right in one go, and the balance you capture on tape is the balance you're stuck with. Nevertheless, most early pop music was recorded much like this (but in mono) — though the luckier artistes could dub their vocals on after recording the backing track.
Pop music is pretty far removed from the way instruments actually sound in a real space, but just about any modern synth can provide a range of good stock sounds, complete with effects, which can be recorded to provide a 'produced' sound. If you have a decent instrument amp, you can use these in exactly the same way as you would an acoustic instrument. However, it's 'real, acoustic' music that benefits the most from the simple, direct‑to‑stereo approach, where the quality of the end result is limited only by your recorder and your choice of microphones.
No matter how much we come to rely on samplers and sequencers, using microphones is absolutely central to making a good recording.
Various types of microphone may be employed, from the famously cheap Tandy PZM (see the box on these elsewhere in this article) up to a battery‑powered, back‑electret model — the AKG C1000S, or the attractively‑priced Audio Technica ATM33a (see review in SOS January '96) are just two examples. Professional recordings tend to be made using more expensive capacitor mics, but these invariably require phantom powering, and phantom power isn't available on hi‑fi cassette decks. There are several different ways of setting up your microphones, depending on what type of mic is available and the circumstances of the recording.
Basic Stereo Mic Techniques
We've covered parts of classic stereo mic techniques in SOS on numerous occasions in the past, but in this article I'm going to recap on the basics (which I haven't covered since the August '92 edition of Recording Musician), before suggesting where each method might be useful.
- THE COINCIDENT PAIR
Also known as 'XY', this is a coincident mic configuration traditionally involving two cardioid or figure‑of‑eight microphones mounted at right angles to each other, as shown in Figure 1. In practice, figure‑of‑eight mics tend to be used only in specialist applications, so for the sake of this article, I'll concentrate on the far more common cardioid or unidirectional mic. Because cardioid mics pick up sound mainly from in front, angling the mics as shown means that one mic will pick up sounds predominantly from the left of the soundstage, while the other will pick up sounds mainly from the right. To make a stereo recording, the output from the left‑hand mic is recorded onto the left‑hand track of the tape recorder, and the right‑hand microphone onto the right‑hand track.
This configuration is called a 'coincident pair', because the two microphones are mounted as closely as possible to each other, so that the sound being captured arrives at both microphones at exactly the same time, regardless of the direction it's coming from. This would only be strictly true if the two mics occupied exactly the same point in space, but for all practical purposes, mounting them next to each other is close enough for most applications. Coincident miking is favoured by many broadcast establishments, because the signals from the two microphones can be added together to form a mono signal without phase cancellations causing tonal problems. The stereo image produced by the coincident pair is not as dramatic as can be achieved using other methods, but the benefit of good mono compatibility should not be undervalued. If you're recording something that may need to be played on radio or TV, then mono compatibility is supremely important, because of the number of mono sets around.
A further benefit of the coincident cardioid setup is that, because the mics favour the sound directly in front of them, the room acoustics are less likely to interfere with the recording, and unwanted sounds from behind the microphones will be attenuated.
If using PZM mics, the equivalent of the coincident setup is to have one mic fixed to each side of a board around 1 metre square (close to the centre, but not exactly at the centre), and to aim the edge of the board at the performers.
- THE SPACED PAIR
A more spacious stereo image can be achieved using spaced microphones, which may either be cardioids (unidirectional) or omnis (non‑directional), and for the purpose of this article, the Tandy PZM can be included in the omni camp, even though it only picks up sound in one hemisphere. The mics are spaced apart according to the width and distance of the event being recorded, and pointed directly at the performers. (Figure 2 shows how this is arranged.) The distance between the two microphones is usually chosen to be similar to the distance between the microphones and the performers, though some experimentation is invariably needed to get the best results. Another advantage of spaced stereo mics is that you can cheat a bit to get the balance right, by moving one of the mics forward if instruments at that side of the soundstage are insufficiently loud.
While spaced mics produce the widest stereo image, they can suffer from mono compatibility problems, so if it is important that the recording sounds good on a mono system, make a test recording and then play the tape back over a mono system — or revert to the coincident miking method.
The Recording
A good recording always starts with a good performance, and for the best sound, the room you choose must have a suitable ambience. Although it may sound obvious, all tuning and maintenance problems should be sorted out before the session starts. Choirs sound better in reverberant rooms or halls, as do classical string quartets and similar ensembles, but if you can't use a local hall, a domestic room with the carpet rolled up, or with hardboard covering the floor, can also sound pretty good.
Most instruments benefit from a live environment, especially if you're not able to add reverb after the event, but you don't need as much reverberation as you would for classical work. An acoustic guitar should sound fine with just a single sheet of hardboard beneath the player, to reflect back some of the sound that would normally be absorbed by the carpet. If you have one particularly nice‑sounding room in the house, exploit it.
Before starting to record, always clean the tape machine, use a new tape for important recordings, and set the recording levels as high as possible, while still leaving a little leeway for any louder‑than‑expected sounds during the performance.
When you're making a live recording, there are two main aspects to balancing the sounds; one is the obvious balance between instruments, but the other is the ratio between the direct sound of the instruments and the ambient, reverberant sound of the room. If you are recording several acoustic musicians playing together and one is louder than the others, your only recourse is to change the position of the musicians relative to the microphones, so that the loudest players are the most distant. The players will probably want to maintain eye contact, so you may end up with the musicians set up in a quite different way to the one they would choose for live performance. Having said that, they'll still need to be spread out from left to right to produce the required stereo image. A useful tip is to keep any bass instruments or rhythmic percussion close to the centre of the soundstage.
It can be tricky balancing the voice of a singer who is also playing an instrument, because you don't have the option of moving one away from the other. If you're working with a solo singer/guitarist, the balance between the voice and the guitar can be fine‑tuned to some extent, by changing the height of the mics so that they point more at the voice or the instrument, as necessary. After each position change, it's best to make a test recording to check balance. If there's more than one singer/player, the changes that can be made by moving the mics are more subtle, so the performers will have to meet you half way by setting their own natural balance. Whenever you move the mics to redress a balance problem, you're likely to upset the stereo image in some way, but in practice, it's better to have a perfect balance than an idealistic stereo spread.
More About Ambience
As intimated earlier, the degree and type of room reverberation affects your mic positions — the closer you get to the musicians, the more direct sound you'll pick up, which means that the room ambience will be less significant. Miking at a greater distance will obviously give a more reverberant sound, but the performance may lose intimacy and clarity if you mike from too far away. In most situations, unless you come across a really good‑sounding room, it's best to err on the side of too little reverb. If, after recording, you feel that more ambience would sound good, you can always copy the tape via a stereo reverb unit.
When working with ensembles, listen to the musicians run through their performance and move around the room to see if you can identify 'sweet spots' that seem to sound better than elsewhere. The larger the room, the more likely you are to find that different locations sound very different, and moving too close to walls or corners will cause an unnatural lift in bass. If you find a spot where the music sounds good, it should also sound good to a microphone, and if you have a good set of headphones, plug these into your recorder so you can listen to the sound as it's being recorded.
When adjusting the mics to vary the amount of room ambience you pick up, don't forget floor reflections, especially in buildings with solid floors and no carpets. Ideally, the microphones should be higher than the musicians, looking down towards them; this way, you'll avoid picking up strong sound reflections from the floor. If you're recording a live concert, you'll also have to find a position that doesn't pick up too much audience noise, which can be a bit of a compromise. Again, you can use height to your advantage, which will help avoid picking up individual audience members who are seated closest to the mics. Anyone who has tried to record a school play will have come across this problem, and it helps if you have a pair of boom stands that can be extended up to eight feet or more.
Summary
You can pick up a lot of valuable experience from trying out these simple mic techniques, and no matter how much we come to rely on samplers and sequencers, using microphones is absolutely central to making a good recording. Saying that mic techniques are no longer relevant is rather like saying a photographer can forget about using his camera, because the end result can just as easily be achieved by cutting out postcards and gluing the bits onto a piece of cardboard.
Small musical ensembles, ideally without an audience, are probably the easiest place to start, then after you've gained a little experience, you could try your hand at recording the local drama group, school play or local orchestra, where you may even find the opportunity for a financial return. By substituting a DAT or even a DCC machine for your cassette deck, professional‑quality recordings can be made with only a little care and experience, and all the techniques discussed here are also applicable to collecting material for creating stereo samples.
The Angle Of Dangle
When working with coincident mics it's important to consider the angle between the two microphones, because if it is too great, you may end up with a stereo image that is all left and right, with very little in the centre. This is what engineers call the 'hole in the middle' effect. On the other hand, if the angle is too small, the sound may have little stereo width.
My own quick solution is to direct the mics at an imaginary point midway between the centre of the stage and the performers at the edges of the ensemble. This will usually leave your mics set up at an angle between 70 and 110 degrees — and it's probably as well not to go too far outside these limits. Every recording is different, so you'll have to modify your initial mic positions based on your own judgement.
Little Buggers: The PZM Mic
Low‑cost PZM mics such as those built for Tandy represent a cost‑effective way to get into stereo recording. Unlike conventional microphones, PZMs have a hemispherical pickup pattern, and must be mounted on a flat surface of around 1 metre square or greater, because the microphone works by combining direct and reflected sound.
The surface on which the PZM is mounted must be of a significant size compared to the wavelength of the lowest frequency to be picked up, otherwise the bass response will suffer. PZMs can be taped to walls, placed on floors or tables, or fixed to movable boards. To record a solo performer singing and playing the acoustic guitar, good results can be achieved by placing two PZM mics on a large coffee table a couple of feet in front of the performer, spaced apart by two or three feet. Figure 3 shows pair of PZM microphones set up in this way.