Paul White shows how you can explore classic mic techniques using basic equipment.
Paul White shows how you can explore a wide range of classic stereo recording techniques using a basic stereo cassette deck with mic inputs and a pair of inexpensive microphones.
The simplest way to make a home recording is to use two microphones to record a complete live performance directly onto a stereo cassette or open reel recorder. This may sound unsophisticated, but in fact it's just about the most accurate way of recording anything. All the best classical recordings are made this way, because, by using just a single stereo pair of microphones, what we record closely approaches what an individual would actually experience when listening to a live performance.
Of course there are drawbacks — the performers have to get the whole song right and the balance between the instruments can't be changed after the recording has been made. Even so, many early records were made in exactly this way, with no added effects and no patching up of mistakes afterwards.
In the case of acoustic music, such as piano or guitar recitals, choirs, chamber music or even folk bands, the direct to stereo approach using a single stereo microphone pair can yield excellent results, even when recorded onto a domestic hi-fi cassette recorder. Various types of microphones may be employed, though the pair used should ideally be the same type and model, and there are several different ways of setting them up.
Coincident Pair: Probably the most popular method of stereo recording is the so-called coincident microphone technique (also known as 'XY' in some circles). This method involves mounting two cardioid or unidirectional microphones at right angles to each other, as shown in Figure 1. 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. The system gets its name because the two microphones are mounted as closely as possible to each other, so that the sound being recorded arrives at both microphones at exactly the same time. This system is favoured by many broadcast establishments, because the signals from the two microphones can be added together to form a mono signal if required. However, the stereo image it produces, while satisfactory, is not dramatic.
Spaced Pair: A somewhat more dramatic stereo image can be created by using spaced microphones; these may either be cardioids (unidirectional) or omnis (non-directional). These 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.) Note that the distance between the microphones is similar to the distance between the microphones and the performers, though some experimentation is invariably needed to get the best results.
PZMs: Tandy's PZM (Pressure Zone Microphone) mics, at around £30 each, represent an ideal way to get into stereo recording, though they are unorthodox in both their appearance and their usage. Unlike most other microphones, PZMs have a hemispherical pickup pattern and must be mounted on a flat surface of around 1 metre square in order to realise their full bass potential. That's because the microphone works by combining direct and reflected sound, and the surface on which it is mounted must be of a significant size compared to the wavelength of the lowest frequency to be picked up.
The microphones can be taped to walls, placed on floors or tables, or fixed to movable boards. To record a solo performer who is, for example, singing and playing the acoustic guitar, it is sufficient to place two PZM mics on a coffee table half a metre or so in front of the performer and spaced apart by a similar distance. Figure 3 shows a PZM microphone and a suitable mounting arrangement.
Given the modest equipment requirements, it is well worth exploring basic stereo techniques before spending more money on a multitrack system. The microphones will always be useful, and if you have to buy a decent cassette deck especially for the purpose, it can still be used in your multitrack studio in the future for mastering or producing cassette copies.
The most important thing to get right is the actual sound of the musicians, so you need to have them playing in an acoustically sympathetic room with all tuning and maintenance problems taken care of before the session starts. Choirs sound better in reverberant rooms or halls, as do string quartets and similar ensembles. Most other instruments also need a live environment to sound their best, but a shorter reverberation time is more normal. For example, to record an acoustic guitar, it may be sufficient to place a sheet of hardboard beneath the player to reflect back some of the sound that would normally be absorbed by the carpet. For home recording, it is worth checking out different rooms to find the one with the best sound, and if you can roll up the carpet in your recording room, so much the better.
If you are recording several 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 ones are further away. Of course there may be some element of compromise involved, because the players will probably want to maintain eye contact with each other to help them with their performance. They'll also need to be spread out from left to right to produce the required stereo picture. As a rule, keep any bass instruments or rhythmic percussion dose to the centre.
In the case of a singer/guitarist, the balance between the voice and the guitar can usually be fine-tuned by changing the height of the microphones so that they favour either the voice or the instrument, as necessary. After each position change, make a short test recording to check balance and overall sound quality.
The amount of reverberation that the room contributes to the recording will be dictated largely by the distance of the microphones from the performers — the closer you get, the more direct sound you'll pick up, relative to the room ambience. Conversely, working at a greater distance will give a more reverberant sound but the performance may lose intimacy.
Unless the room has a good live sound, you'll invariably be better off miking fairly close to the instruments to exclude the room sound. If, after recording, you feel that more ambience would have benefited the performance, you can always copy the tape via a stereo reverb unit to add a little artificial ambience — but take care not to overdo it.
In finalising the microphone positions when working with ensembles, listen to the musicians run through their performance with your eyes closed, so you can concentrate on the the sound being produced. Check out different places in the room and see if you can identify 'sweet' spots that seem to sound better than elsewhere, especially if you're recording in a large room or concert hall. Ultimately, if you can find a spot where the performance sounds good to you, it should also sound good to a microphone. If you have access to a good set of headphones, you can plug these into your recorder to check the sound that's actually being recorded.
Aside from the microphone distance from the performers, you also have to decide how far from the floor to position the mics. 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 that might adversely colour the sound of your recording.
If you're recording a live concert, you'll also have to find a position that doesn't pick up too much audience noise. Some audience noise will add to the atmosphere of the recording, but the last thing you want is to pick up the conversation of the people sitting closest to the mics. Again you can use height to your advantage and you may even be able to suspend the microphones from the ceiling, to avoid your stands obstructing the audience's view.
You'll also need to consider the angle between coincident microphones, because if it is too large you may end up with a stereo image that is all left and right with very little in the centre. Conversely, if the angle is too small, the sound will be narrow, almost like mono. As a rule, the mics should point roughly between the centre of the stage and the performers at the outside of the group; any angle between 70 and 110 degrees should produce satisfactory results. Likewise, the distance and spacing of spaced microphones will need to be adjusted to suit the prevailing circumstances. Every recording is different, so don't be afraid to use your ears and move the mics about until you're happy with the result.
There is a lot to be learned from applying these simple, stereo miking techniques; though more and more pop music is being produced electronically, the correct usage of microphones is at the heart of recording — even with the inexpensive Tandy PZM mics, exceptionally good results can be achieved. You might care to experiment further by recording drama, live sound effects or outdoor 'scenes' in addition to musical performances. All of the equipment necessary can be utilised if you decide to progress to a more sophisticated recording setup, and the experience gained will be very valuable.
Small musical ensembles are probably the easiest to start with, acoustic duos or small folk bands being ideal. After you've gained a little experience, you could try your hand at something a little more ambitious, such as recording the local drama group, school orchestra or play. It's also interesting to try out solo recordings of unusual instruments, so if you have a strong ethnic community in your area, see what you can find; it doesn't all have to be acoustic guitar and vocals — tablas and sitars are just as much fun!