|Getting Rid of Problem Vocal Pops (Plosives)
Written by Bill Gibson - © 2005, Cengage Learning. Reprinted with Permission.
This article is an excerpt from the following book: The S.M.A.R.T. Guide to Recording Great Audio Tracks in a Small Studio.
Sometimes even using a good wind screen won't eliminate all pops—or you might have opted to keep a take for musical reasons, in spite of a plosive problem. Try the following three techniques along with, or instead of, a wind screen.
1. Move the mic slightly above or below the singer's mouth. This will get the air moving past the diaphragm instead of moving directly at it. There might be a slight sound difference, which could be either detrimental or beneficial, but this is typically a good way to avoid pops.
2. Point the mic at an angle to the vocalist. This position, like the previous suggestion, allows the air to move past the capsule instead of at it.
3. Move the mic very close to the vocalist (closer than two inches). The movement of air doesn't reach its peak energy until it's gone more than an inch or so from the singer's mouth, so you might be able to position the mic at a point before the air achieves maximum flow, therefore avoiding pops. Positioning the vocalist close to the microphone works best on moving-coil microphones. Condenser mics suffer from close proximity to the singer because the moisture from the vocalist has an adverse effect on the sound and operational status of the mic.
Sometimes, if you've tracked the vocals with the bass or drums turned up artificially high in the monitor mix, a plosive problem can go unnoticed until mixdown, when you begin isolating parts. It might be possible to bring the original vocalist back into the studio to repair
the track, but you might not get the same sound or emotional impact that you got on the original take.
One simple solution is equalization. The pop that happens as a result of the strong plosive is heavy in bass frequencies, usually below 100 Hz. If you're quick with the EQ controls you can often turn down the lows at the precise word or part of a word where the problem exists. This technique is very effective and especially useful when you only have one or two problem spots to focus on.
Electronic Plosive Repair
Sometimes simply turning down the lows at the problem spot makes the vocals sound thin and unnatural. Or maybe there are too many complex spots to fix. If you're having big problems like these, electronic plosive repair is definitely worth a try. (This technique will also get you used to using processors creatively and efficiently.)
This kind of repair requires the use of an equalizer and a compressor/ limiter with external triggering capability. Follow this procedure:
1. Plug the output of the problem vocal track into a mult in the patch bay or use a simple Y cord to split the output of the track.
2. Patch one output of the mult or one side of the Y cord into the input of the compressor/limiter, then patch the output of the compressor/limiter into a line input of your mixer's channel line in, fader in, and so on.
3. Patch another output of the mult or the other side of the Y into the equalizer input. Outboard graphic or parametric equalizers work best for this technique because they typically have the greatest ability to zero in on a problem frequency.
4. Plug the output of the equalizer into the input of the compressor labeled external input, external, key input, or key. We already have the vocal track patched through the main ins and outs of the compressor. In normal operation, the compressor/limiter turns up and down in response to the audio signal coming into the main input. We're setting the compressor up so that it will turn up and down in response to the signal that comes into the external input. When the internal/external switch is on internal, the processor works normally, responding to the signal that comes into the main input. When the internal/external switch is on external, the processor responds to whatever signal is coming into the external or key input.
5. Set the equalizer so that the bass frequencies are boosted. If you can listen to the output of the equalizer, adjust the EQ so the plosives are as obnoxious as they can be.
6. Set the internal/external switch to external or push the key button. By pressing the external or key button, we're telling the processor to respond to the signal we've patched into the external or key input, instead of the signal that's actually running through the main ins and outs. Because the equalized signal has accentuated the plosive problems, we can adjust the processor controls so that the VCA (voltage controlled amplifier) only turns down when the plosives occur. This gives us an automatic pop remover.
7. Set the ratio control to about 7:1.
8. Set the attack time to fast.
9. Set the release time to medium-fast.
Play the section of the tune that contains the problem plosive and adjust the threshold control so that gain reduction is indicated on the gain reduction LEDs every time the plosive occurs. We want gain reduction to occur only when the problem plosives happen. This might take some fine adjusting of the threshold, but because the trigger is responding to the external input that contains the equalized version of the track, and the equalized version of the track has highly exaggerated plosive problems, it's almost always possible to successfully repair problem plosives using this technique.
If there's a problem, readjust the EQ Turn more bass up, turn a different bass frequency up, or turn the highs and mids way down. You can get the compressor set so that the only time the gain reduction LEDs show gain reduction is when the plosives occur. When you adjust the equalizer that is patched into the external input, you're not affecting the tone quality of the track. The main input and output of the compressor are not being equalized by this technique.
You're just sending an exaggerated EQ to the VCA to trick the unit into responding when you want it to instead of when it would normally.
Once these adjustments are completed, the compressor should automatically turn the track down every time a problem plosive occurs. The rest of the track should be left unaffected by the processor.
If you own a compressor that has a side chain insert (sends and returns or ins and outs other than the main inputs and outputs), you can de-pop a vocal track with fewer steps. You only need to have an equalizer; it's not necessary to use a mult or a Y chord. The side chain output is a separate send of the signal that's coming into the compressor.
Follow this procedure if your compressor/limiter has a side chain.
1. Plug the output of the problem track into the main input of the compressor.
2. Plug the main output of the compressor into a line input of the mixer. (This is the patch for normal compressor use.)
3. Plug the side chain output (send out) into the input of the equalizer.
4. Plug the output of the equalizer into the side chain input (return) of the compressor.
5. Set the internal/external switch to external or key.
6. Adjust the equalizer that's patched into the side chain to boost the problem frequencies.
7. Adjust the ratio, attack time, and release time to the desired settings (probably about 7:1 ratio with fast attack and medium-fast release).
8. Adjust the threshold so the gain reduction LEDs only indicate gain reduction when the problem plosives happen.
For more information, see The S.M.A.R.T. Guide to Recording Great Audio Tracks in a Small Studio.
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