Making the Most of... (Part 2)
Bass Guitar and how to record it.
Bass guitars have the reputation of being comparatively easy to record. There are, however, many techniques available to help you achieve exactly the bass sounds you require.
By way of an introduction, it is perhaps worth detailing a few salient facts regarding the use of bass guitars in a recording environment. Whenever a band rings up to book a session, I always enquire as to the line-up, whether they use bass guitar or bass synth (or neither) and if the answer is bass guitar, I'm usually struck by several conflicting emotions. One is pleasure, for speaking in my capacity as an engineer the bass guitar is one of the easiest instruments to record. Since a distorted bass is usually not required, it can be plugged directly into the mixing desk, thus eliminating problems such as spillage (which plagues drum kits). At the same time, the sound of the bass guitar has changed surprisingly little since it first became popular in the late fifties (when you consider the various sound fashions the guitar has passed through). Perhaps this is because everyone's idea of a good bass sound is surprisingly similar - a testament to the fact that it is an instrument that fulfils exactly the purpose for which it is intended. At any rate, it is fairly simple to approximate the sounds currently in vogue amongst the famous even on fairly basic equipment (unlike synth players who want to sound like Frankie goes to Hollywood on their Casio 202s). When you do get a good sound, bass players are usually fairly pleased, unlike guitarists for whom the sound is never exactly as they imagine it.
The second emotion is apprehension, because the glowing picture I've just painted is never quite the way it turns out. All too often, what should be a creative process becomes a rescue mission to salvage a half decent bass sound, due to the appalling standard of both instrument and playing technique. That isn't to say that there aren't a lot of excellent bass guitars around, with many excellent guitarists. It's simply that frequently, the bass seems to be neglected in comparison with other instruments. Sometimes poor amplification is used at the rehearsal stage and fails to reveal deficiencies in both instrument and the player. If the sound is dull, then the poor quality amp may be blamed - the last thing that is considered is a new and brighter set of strings. On the subject of strings, lead guitarists are often very particular about not only the gauge of the strings he uses, but also the make. Without wishing to generalise, it seems to me that the average bass guitarist would quite happily use wire netting if he happened upon some suitably sized pieces in the road! If by chance a new bright set of strings does reach over from a shop doorway and slap him in the mouth, when he winds them on and discovers his bass has lots of squeaks and buzzes that were absent before, the new strings will be blamed rather than poor playing technique.
If so far this article has not made you glance downward in a guilty fashion, then read on and I will try to explain what can be done with the humble bass.
These days this is really the only place to begin when discussing recording the bass guitar, and if you want that punchy sound so popular at the moment I am afraid that it's something which you'll have to consider. Basically a compressor is a dynamic device in which gain reduction is automatically controlled by programme level, increasing attenuation progressively as the level rises above a pre-determined point. What this means in practice is that a pre-determined level is selected (the threshold), and every time the signal rises above this threshold, the compressor starts knocking it back again. The more the signal rises, the more the compressor reduces the level (controls are usually available on the compressor to determine the rate at which the device cuts in and out once a signal has exceeded the threshold as well as the ratio of compression).
The second method relies upon the dynamics of the compressed bass. Because they have relatively sharp attack and decay times, bass guitars are fairly easy instruments to gate - more so with heavily compressed instruments because the threshold level of the noise gate can be set fairly high, with little risk of the bass accidentally triggering the gate in a quiet passage.
I will only refer to the third method in passing because it is fairly specialised and can be expensive (unless you build your own from a Tantek kit) and that's the use of dynamic filters. These devices progressively attenuate the high frequency content of a signal as it's level drops, so that hiss is not a problem during quiet or silent passages. Correctly used, a dynamic filter can be far less obtrusive than a noise gate.
Equalising a bass need not only be corrective though. Even using a professional quality guitar, judicious EQ can sometimes make an astonishing difference. Personally, I have always found that boosting frequencies from 60-100Hz, cutting those from 150-770Hz then boosting those around 7kz can give a punchy bass end and bright top end with no muddy middle frequencies to interact with other rhythm instruments (which usually occupy the same frequency bands). The amount of cut or boost depends on you of course - if you're using a graphic it helps to try and create a rounded curve if you can. With slapped bass though, a certain amount of midrange cut can be used to good effect.
A final word. If you do like your bass bassy, then beware of equalisation before it goes on to tape - it can cause distortion as I have said. It is preferable to add it during the mixdown, when you might decide you didn't need it after all!
Dramatic equalisation can compound any noise problems, thus making some sort of noise reduction necessary. For those of you unfamiliar with noise gates, imagine a fader which opens every time the bass plays, and shuts down the instant it stops. While it is open, the signal is totally unchanged, but when it shuts no signal at all gets through. Various parameters are controllable on a noise gate in order to make it respond in accordance with the dynamics of the processed signal - ie. in the case of a bass guitar fast attack (open) and fairly fast decay (close). With the gate in operation, every time the bass plays the signal is recorded, but when each note ceases, no matter how short the interval, the gate closes and all compression and equalisation noise is cut out! Such noise is still present when the gate is open but is inaudible above the level of the bass itself.
Noise gates can also be used with the bass creatively as well as correctively. Most gates can be triggered (ie. made to open and close) from a source other than that being processed. The gate may be triggered from a bass drum for instance. Every time the bass drum plays, the bass guitar is heard through the open noise gate thus the bass drum and bass guitar sound very tight, since they play exactly at the same time every beat. A little experimentation might prove worthwhile (alternatively you can trigger another instrument from the bass guitar - causing a sustained keyboard to play in time with the bass for example).
Until fairly recently, the only effects used on the bass guitar tended to be non-audible, ie. dynamic processing devices such as compressors, gates or expanders. The reason for this lay partly in the fact that due to the frequency response of the instrument, high quality processors were required to successfully process the lower frequencies. At the same time, the sound of the bass guitar was so clearly defined in the mind of producers and engineers that tampering was frowned upon. One processor which did manage to gain some acceptance was the phaser. It was even incorporated into some bass amp designs. However, phasing can cause bass loss as it sweeps the harmonics.
As far as recording goes, the modern bass guitar has three main problem areas. The first concerns the frequencies over which the instrument is active (it has a fundamental frequency range from about 40hz to 300hz with harmonic frequencies extending some way beyond that - to about 10kHz). As the name implies though, the predominant frequencies are in the bass end region. Unfortunately these are precisely the frequencies which are prone to overload and distortion in recording situations. The second problem area is born in the fact that on many bass guitars, even some good ones, the bass strings tend to boom, whilst on the top string, especially in the higher regions not only is there little bass response, but there is often too little sustain as well. You are left with an instrument which encompasses large ranges of sustain and a wide (and therefore difficult to record) frequency response. The third contemporary problem with bass guitar lies in the current trend towards slapping the instrument. Not only is a good bass end required, but also a smooth but crisp top end. Such frequency demands usually necessitate some ancillary equalisation - a graphic or parametric for example (which I shall come to presently). This means that even larger frequency ranges are recorded on to tape, and in order to minimise risk of distortion, levels have to be kept fairly low. In addition, the technique of slapping involves frequent peaks above those normally expected from a bass guitar, thus reducing the recording level even further.
Given the ability of a compressor, you can begin to realise how this might relate to the problem areas of bass guitar recording. Firstly, the risk of any distortion caused by tape overload is removed and at the same time, a very high signal level can be made possible. With heavy compression, every time the bass level overshoots the selected threshold, the compressor pushes it down again. This means that large EQ ranges and varied playing techniques (such as modern slapped bass) can be easily recovered without fear of overshoot and without risk of compromising signal to noise levels. At the same time, when the signal level starts to drop, (ie. the note dies away) the compressor appears to keep boosting it, giving much greater sustain and smoothing out 'boomy' bass and 'plinky' treble. The use of compression in bass recording has become so universal that it is practically impossible to duplicate the sound you hear on record without using one.
In general, the amount of equalisation needed when recording a bass guitar increases in inverse proportion to the quality of the instrument and/or the playing.
Boosting higher frequencies on the desk (or via a graphic or parametric) can help, but unwanted noise will also be boosted. Such increases are barely tolerable at the best of times, but if a compressor is used, they can increase to ridiculous levels. So what can you do about it?
I've found that three methods help to combat this. Firstly, if you're correcting the equalisation via an external processor, you can practically cut every frequency above 12kHz if you're desperate. It sounds a bit drastic when listened to in isolation, but within a multitrack mix it can be difficult to notice. Obviously the amount of high end cut you make depends upon the scope of your equaliser. On a 31-band graphic, for example, you can cut 10kHz, 12.5kHz, 16kHz and 20kHz, rolling off as much or as little as is required of each. On a 10-band graphic though, you only have a choice of 8kHz or 16kHz. With parametrics you don't have this problem to the same extent, and the results are dependent on the frequencies the device will reach and the bandwidth of cut or boost available.
A modern alternative is flanging, but it is almost impossible to flange the bass with any subtlety. It simply sounds as though the EQ was not properly adjusted! Deep flange, created by using longer delays (of the order of 16ms), can make a bass sound amazing but can become tedious if overused.
Chorus is at the moment my favourite effect to use on bass. Even a cheap chorus pedal can open up the sound, making it richer and more vibrant. Beware of overuse (ie. making the chorus too deep) as the pitch wavering effect can be quite sickening. A variation on this theme is shifting the pitch of the bass down an octave and blending it with the original signal. If you don't have a harmoniser, then cheap octiviser pedals are available. This effect can be very effective, particularly when played in the upper registers, but is best used on odd phrases rather than on the whole bass track. Alternatively try recording another bass line an octave below the main one to get some idea of the sound.
Echo is not usually used on the bass except for special effects as it tends to complicate and muddy the sound. Reverb however, especially with a very short decay time can give a warm ambient sound, on fretless basses in particular.
Whether you decide to direct inject the bass or mike up an amp and cab largely depends upon the sound required. Other factors such as the quality of the instrument itself do play a part. Plugging directly into the desk will give a much clearer signal but can be a disadvantage if a lot of string noise (high frequency) is produced during playing. New strings are particularly prone to this.
Bass cabs tend to have fairly limited frequency response, and much of the string noise disappears into the general colouration introduced by the amp and cab. A graphic equaliser can perform a similar job if direct injection is required. The problem involved in miking up bass cabs is that they are often prone to buzzes, mains hum or speaker rattle which are very noticeable, even in the mix. Some engineers compromise by recording the amp and cab as well as direct injecting using a splitter box. Personally, I prefer the extra seperation gained from direct injection. Unless you are DIing the bass via an effects pedal (or unless the bass is active) the mixer input impedance may well be too low for correct matching, resulting in treble bass or a generally dull sound, if this is found to be the case, try an active DI box, a pre-amp type pedal, or use the line output from your amplifier if it isn't too noisy.
It is worth pointing out that many effects such as flanging, phasing or chorus are primarily audible in the upper frequency bands and direct injecting preserves these upper frequencies whereas amping can attenuate them. If playing the bass through an effects box therefore, direct injecting the instrument is usually preferable.
A list of suggested settings follows. Don't stick faithfully to them; it is worth experimenting. After all, that is the only way that new techniques are developed and new sounds created. Don't forget the golden rule of bass playing; if all else fails and you still can't get the sound you want - plug in a synth!
Compressor - Ratio 15:1, Attack 0.5ms, Release 0.5s.
Noise Gate - Attack 0.03ms, Release 1s.
Equalisation Boost - 63-120Hz, 4-6.3kHz, Cut 250-630Hz.
Phasing - Deep to Medium Speed (Experiment).
Flanging - Delay 16ms, Width 60%, Speed 1kHz.
Chorus - Delay 20ms, Width 10% Speed 1kHz.
Reverb Delay Time - 0.25s.