The voice as an instrument is one of the most challenging to record satisfactorily due to the large dynamic range and the number of variables that affect the sound before it reaches the microphone. There are a number of things that the recording engineer can do to ensure that the voice is recorded a manner which produces a good raw sound which can be manipulated, if necessary, at mixdown.
The first factor, and often the most overlooked, is the acoustics of a room. Sound will reflect off walls, floors and ceilings in a room, and therefore some of these reflections will reach the mic at some point, albeit momentarily later than the original sound. This will have a massive influence on the recorded sound. A small /boxy room will often produce a boxy sounding vocal and this is common on many home recordings. Some smaller rooms with many hard surfaces will also produce ‘flutter echo’s’. This hard ‘metallic’ sound is very unpleasant and can ruin a vocal take. Many places in your home are likely to have a flutter echo, most commonly stair wells and box rooms. An easy way to identify this is to click your fingers or clap your hands and listen out for a ‘metallic’ ringing after the initial impulse.
As most home studio vocals will be recorded using a mic with a cardoid polar pattern, there are a few things that can be done to improve the sound of the room. As cardoid mics reject sound from the rear of the mic, the front side of the mic is where the mic will pick up the most unwanted room reflections. Bearing this in mind, it makes sense to ensure that the wall behind the vocalist is treated in some way to absorb as many reflections as possible. Acoustic tiles are widely available although somewhat expensive and also require permanent or semi-permanent installation – not ideal if you live in rented accommodation or record in your living room! The most inexpensive way to achieve a somewhat similar goal is to hang a duvet/blanket/sleeping bag etc behind the vocalist. Obviously you want as much coverage as possible on the surface behind the vocalist, and also above head height is important. In a worst case scenario you could place your vocalist in front of your curtains (they should be drawn as glass is, obviously, highly reflective).
The positioning of the vocalist/mic in the room is also important. As you want to cut out reflections into the mic, the vocalist should be placed away from any walls/surfaces. However you also want to ensure that the vocalist/mic is not dead centre in the room as this is where standing waves will be most prominent. An ideal position would be a few feet away from the centre of the room. The best way to determine the optimal mic position is by making some test recordings with the mic/vocalist in different positions in the room. Listening back to the recordings should help you identify the ‘sweet spot’ in your room.
It goes without saying that you want to record vocals in a room that is relatively quiet – sensitive microphones will certainly pick up the fans in your computer, the rumbling of traffic outside and a radio being played loudly elsewhere in the building.
The majority of professional vocal recordings are made with capacitor/condenser microphones rather than their dynamic counterparts. Capacitor mics offer many tonal advantages over dynamic microphones and are particularly suited to recording vocals due to their improved high frequency response. There are occasions when a dynamic mic may be more suitable – if a band are after a recording that reflects their live performances it is not unknown for the vocal to be recorded with a dynamic microphone such as the Shure SM58.
In practice a capacitor mic will usually be preferable for the majority of vocal recordings. The nearest thing to an industry standard in the professional market is the Neumann U87 although this is out of reach for the majority of amateur engineers. The last few years however has seen a flood of Chinese-made capacitor microphones into the market, many available at under £/$100. There are also other established American, Australian and European brands who now offer mics as low as £/$150.
As mentioned earlier, it is usually preferable to pick a microphone with a cardioid polar pattern as this rejects sound from the rear of the mic therefore eliminating most of the unwanted sounds reflecting from the rear wall. If you are working in an acoustically ideal environment then it is possible that you may want use a microphone that shows off the acoustics of your room a bit more – omni-directional microphones are typically used for this purpose.
Cardioid mics do exhibit some unique behavior, and the most well known is the ‘Proximity Effect’. When using a cardioid microphone at close range, less than 3 or 4 inches for instance, the low frequencies will be exaggerated and this is what is known as the proximity effect. This can be used to your advantage if recording a vocalist with a ‘thin’ sounding voice – moving the vocalist closer to the mic will increase the low frequency content of the signal. This effect can also be used when recording spoken word for voice overs etc. Usually a distance of between 6 and 10 inches will produce optimal results without coloration from the proximity effect.
The use of a shockmount is a good idea to prevent mechanical vibrations reaching the microphone – most of these come from low frequencies being transmitted through the mic stand and into the microphone. Generic shockmounts are available now which should fit most mics and are much more affordable than many manufacturers proprietary designs.
A pop-shield is another worthwhile purchase if you intend to record a lot of vocals. A pop shield prevents ‘plosives’ (such as P and B sounds) which manifest with a low frequency burst of energy. A pop shield is best positioned at least 1 inch from mic. The positioning of the shield can also prevent the vocalist getting too near to the mic and triggering the proximity effect. Budget pop shields can be had for as little as £/$10, although if you can’t stretch to this then there is always the coat-hanger and pair of tights method which is as popular as ever in home studios.
When setting the gain on your mixer, try to ensure that the average level of the vocal is around the 0dB mark – this should leave enough headroom for louder passages without distorting.
If you are recording onto a digital medium it is imperative that you leave enough headroom to allow for louder bursts. Unlike analogue, digital is unforgiving to clipping and a take can be rendered unusable by digital distortion. Recording at 24-bit is preferable for dynamic sources such as the human voice as you can afford to leave more headroom due to the increased dynamic range. A small amount of compression before your recorder (commonly from a channel strip or hardware compressor) can help prevent the signal from overloading your recorder but it must be carefully applied as any changes made to the sound during the recording process can not be undone at a later time. For more information on the Recording Chain click here.
Finally, the vocalist must be happy with their headphone mix. A little reverb in the headphones can aid tuning, and creating the right mix between vocal and backing track can help coax the required performance out of the vocalist. Too little of the vocalist in the headphones might cause the singer to push too hard and this can cause problems with timbre and sometimes pitching. Too much of the vocalist in the headphones may cause the singer to perform too timidly and not achieve the desired results.