A consistent sound in your lower frequency range is really important to your Sunday morning mix. The human ears perceives higher frequencies louder than low frequencies but the audience is quick to notice when a low frequency sticks out and rumbles them in their seat. Basses can be very finicky instruments and often times the neck of particular bass will have dead areas as well as resonate areas. Your bassist may play an open A on the second string and it feels full and powerful then when he moves up the neck to play a D on the fifth fret it feels empty. The opposite problem is just as bad: one note on the neck resonates in the room and sticks out compared with the rest of notes on the bass. Using compression with a problem instrument like this can be a life-saver. Using compression on a good sounding instrument can take it from good to great. Lets take a look at a few situations and approaches to applying compression to the bass guitar.
The Ideal
For most material performed on Sunday morning the ideal situation is a bass player that has a confident and consistent touch. Compression in this scenario will usually be a minimalist approach. You only need to enhance what's already there - you're adding the glue that holds the low-end together. Lets break down what happens when a bass string is played.
The initial transient is loud and full and then the sound begins to decay slowly. Depending on the song and performance this natural decay of the note varies. One of the goals in compressing a bass is an effort to make that note decay slower so that the bass is heard and felt longer than it naturally would be. For this intent we will use a ratio of 6:1 with a slow attack. You'll want to set the attack so that the compression begins just after the initial pluck of the bass. While the bassist is playing, adjust with the threshold slowly and you should hear the bass getting fuller and “longer” as you lower the threshold. Careful not to go to far because at certain point you will be compressing too much and the bass will actually begin to sound smaller and less dynamic. This type of “crushing” sound is not good in this situation. Watch your meters - you want to see your gain reduction meter engaging just after the initial pluck of the string. In this way the compressor is helping the bass sustain for longer until the next pluck of the string, creating a fuller sound.
I typically start with the release to the slowest setting then I adjust for the performance. I like to see the gain reduction just beginning to let off before the next hit. This whole process is more art than science. Start your attack, release and threshold at given point, then adjust and experiment.
A Blue Stripe 1176 has a bit more grit and will even break up a bit when pushed
A Problem With The Bass
If I'm trying to fix an uneven bass sound, then I really have to be attentive to the performance. Sometimes you might have only one or two notes that stick out so keep the performance material as your context. If you ask your bassist to play all by himself and the player begin to perform a slap bass part that has no relation to the songs being played that Sunday morning, you are doing very little to help your mix. Work on the bass sound while the band is rehearsing so you can hear what your changes are doing to your Sunday mix. Typically I'll ask the bass and drums to play a chorus section over and over until I'm happy.
I like a higher ratio in this problem situation and 10:1 is a good place to start. Use a medium attack and release time. This is so that the compressor will only start once the frequency begins to stick out. If the compressor kicks in too soon then you will compress notes that are not the problem. Set the threshold so that the compressor is just barley engaging during normal performance, maybe 1 or 2 dB. You should notice that once the problem note is played that signal increases and the compression kicks in to reduce the problem frequency.
A Problem With the Player
Suppose you have a young bass player who plays pretty hard at times, or maybe they play with a pick all of the time. In both of cases you are going to have a very dynamic sound with a lot of attack. When a bass is played hard all of the time, you'll often find that the sound “bottoms out” and bass lacks low end. In this case, instead of trying to enhance the sustain of the instrument the goal is to reduce the initial transient being played. A fix for this situation is to use a faster attack and release time so that the compressor engages right away knocking down those fast transients. The ratio will be need to be adjusted according to how hard the performance is. Start out at 4:1, use your ears and adjust accordingly. Be careful to set the threshold properly. For a picked bass you want to see the compressor engaging right away. For a dynamic player it should engage when a note is played particularly hard. If your compressor is kicking in on lighter touches by the bass player, then the threshold is probably set too extreme and you should back it off a bit. When this technique is properly used there should be less of an edge on the bass it should sit better in the mix.
Typically I’ll ask the bass and drums to play a chorus section over and over until I’m happy.
Compression for Character
The techniques described thus far have to do with using compression to enhance or fix the bass. If you are mixing with plug-ins or if you have multiple options of outboard compressors, then you can approach bass compression with a bit a of a different mindset. In the same way that certain effect pedals are found by a guitar player to be favorable with a given guitar and amp combination, with experimentation you will find that a given compressor will have qualities that relate well with a bass guitar.
A Blue Stripe 1176 has a bit more grit and will even break up a bit when pushed. In this way some people like that sound to give the bass a bit of overdrive. A LA-2A compressor has a round, warm tone that can suit a bass guitar well. This is a classic sound that you've heard on countless records.
You may not have those tools at your disposal but you may have a few different outboard compressors to pick from. Use the techniques described above with the understanding that one compressor may be a better for the bass guitar than another. The best thing to do is experiment and let your ears be the judge.
When working on these techniques keep in mind that compression is rarely a “set it and forget it” situation. One bass setting is not a magic setting for all basses at all times. So don't approach compression on bass as a one size fits all solution. When in doubt, remember that less is more. The only thing worse than a bad bass sound is compressing it till it has no life left in it.
