Multiband Compressor For Vocals

[Ariane Delbrune]

Onceyou've set your threshold so that gain-reduction is triggering reliably just on the transients, you can then refine the compression ratio to rein them in to taste. I'll regularly use ratios upwards of 5:1 here, and you may need gain-reduction values of 12dB or more in extreme cases to smooth extra-prickly recordings, especially if you're generally boosting the brightness of your guitar or drum kit for mixing purposes. This might seem like over-processing, but in practice the speed of the gain reduction is so quick that it won't be anything like as audible as you'd expect. A critical setting in this scenario, however, is the crossover point between the compressed band and the remainder of the spectrum: set it too high and you won't be able to reduce the subjective spikiness enough, because some of each transient will be making its way past the compression; set it too low, and gain-pumping artifacts from the heavy processing are more likely to impinge on the main body of the instrument's timbre.

One trick here is to mute the processed band for setup purposes, because that makes it easier to check whether it's catching all the offending sibilance, and then to narrow the processed band's frequency bandwidth as far as you can without letting any harsh 's' frequencies through. If you're careful with this part of the setup, you're less likely to get unmusical lisping or gain-pumping artifacts with the processing once you unmute the processing band. Mind you, it's rare in my experience to find an over-sibilant vocal that you can process satisfactorily with set-and-forget processing, even when you're using multiband processing like this, so I normally end up automating the processing threshold occasionally to make sure the band's gain-reduction remains in the sweet spot.

In both these events, a fairly narrow-band compression setup targeted at the most harsh-sounding region has a lot to recommend it. In a sense, the processing is very similar to a de-essing scheme, and the only real challenge is homing in with sufficient accuracy on the offending frequency range. I find spectrum analysers quite good as diagnosis tools here, but if you don't have anything sufficiently high-resolution on hand, then a narrow EQ band swept through the mid-range spectrum can also help. (That said, I'd recommend using a cut rather than a boost, because almost every mid-range frequency can start sounding harsh if you boost it with enough EQ, so it's easy to end up chasing your tail that way!)

In some cases, particularly with vocals, more than one frequency region may be contributing abrasive moments, in which case you may need to use two bands of processing to get sufficient tonal smoothing without unacceptable loss of presence to the vocal tone as a whole. Bear in mind, though, that you may not be able to get enough control in that scenario unless your particular multiband processor has reasonably steep crossover slopes between its bands. (I'd be looking for something upwards of 18dB/octave for that kind of forensic work.)

Another common situation where I often reach for LF-specific compression is when dealing with upright bass and electric bass-amp recordings. Miking either of those instruments in a project studio environment can result in your capturing a room resonance around the 70Hz region (corresponding to typical domestic ceiling heights of 2-2.5 metres). This resonance will respond differently to notes of different pitches and durations, resulting in low-frequency level inconsistencies. With upright basses, there may be an additional resonance around that region from the instrument's main cavity air resonance. Setting a multiband compressor's low-frequency band to control the bass spectrum below about 100Hz can help rein in the low-end of any notes which happen to excite the unwanted resonance.

Just because the bands are there, doesn't mean you have to use them all. It's best to identify the specific problem you're trying to solve, and then use as few bands as possible to reach the desired result.

Even with DI'd bass, though, I've sometimes had problems with up-tempo songs where the player taps their right-hand fingers on the strings while playing (to maintain their sense of rhythm during performance), thereby generating powerful sub-bass thuds that can potentially overpower the kick-drum in the balance. Again, a low-frequency compression setting can help address this at mixdown, ducking the sub-bass thuds while leaving the fundamentals of the proper bass notes comparatively unscathed.

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I've been trying to nail down some "go to" settings for the multi-band compressor in Audition, applied specifically to my VO tracks. I know that this is largely subjective, but I'd love some foundational settings that I can build on. I have done a bit of research on this, and most of what I find is more for vocals and not so much narration. I'm sure that my frequency levels are not correct for most voice ranges. I also find that I'm making a lot of my voices more harsh rather than just having a good presence.

With the proper use of EQ you can shape the vocal to perfection. You can help the vocal to cut through the mixwhilst improving the tone. As the vocal is often the most important element ina song, a well-mixed vocal can make a significant difference to the end mix.

For this reason, multiband compression isthe perfect tool for further shaping the tone of a vocal part. With multibandcompression, you can reduce and control certain elements of the tone only whenthe issue appears. EQ, on the other hand, is static and affects the wholetrack.

This increase in volume usually representsa room resonance. Leave the EQ band where it is and lower the gain to apply a2-5dB narrow cut. Bypass the EQ to check the difference and you should noticethat the vocal sounds cleaner and clearer with the cut engaged.

I normally find at least one resonancebetween 300Hz and 1kHz to cut. You might also find some nasty resonances in theupper mid range worth cutting. Apply the same process again but sweep between1kHz and 6kHz.

I recommend applying compression to the vocals after yoursurgical EQ plugin, and then using a second EQ to apply subtle tonalcorrections. This time, try to avoid sweeping around with a strong boost.Instead, think about how you want the vocal to sound.

Load up a professional track in a DAW or another audio player and compare the track to your mix. Consider how the vocal sounds different, whether the vocal needs more air and brightness or if it soundmuddy and undefined.

High-end studio microphones sound muchbrighter than most affordable microphones. This silky top end makes the vocalsound expensive and bright. You can replicate this character of sound byusing an analogue modelling EQ to boost the top end.

Now that you've shaped the general toneof the vocal, have a break before coming back to listen to the entire track again.Turn the monitor off or close your eyes. Listen out for any tonalinconsistencies, or moments where the vocal starts to sound muddy,sibilant or thin.

The first step is to find the offendingfrequencies. Loop the section where the problem appears and use the sameboost-and-sweep technique to find the frequency range where the problem occurs.As before, you will notice an increase in volume when you find the bad range.

One compressor is hard enough to get your head around. Strapping a stack of them together is almost cruel on us poor producers. How are you really supposed to use multiband compression, and what can it really do for your tracks?

The most common application of multiband compression in a production context is probably creating conformity in an uneven recording. This might be a bass instrument which loses bass in higher notes, or a vocal recording where the singer struggles with mic technique and drifts away from the mic occasionally.

By aggressively compressing the lower frequencies while still allowing higher frequencies dynamic range, we can achieve a consistently present low end, while mids and highs can continue their more expressive dynamism. Bass frequencies can be compressed more aggressively since we like to perceive them as a thick blanket of sound. The articulation in bass sounds comes from the low-mids, mids and higher frequencies.

With vocals, we can compress the mids more aggressively than the lows and highs, which may help to bring out the vocal itself, even when the vocal is quieter. By choosing to apply much less compression to bass and highs, we avoid squeezing muddy lows and noisy highs when the midrange compressor needs to work harder to bring out the vocal itself.

Mixed In Key Studio Edition tells me in seconds that the original track is in C Minor, and has a predominant notation profile of C, D and G. Other notes are present, but I can be confident that a bass drum that registers in either C, D or G will sound in tune.

By using softer ratio and threshold, we are making the compression effect a lot more subtle. It means the ducking will be almost transparent, but should help the vocal lift itself from the sub mix, which is always a good thing!.

To solve this, we can of course use a traditional compressor to tame the spike. But the degree to which we may need to squash the spike sweep might also crush the bass frequencies more than intended. A multiband compressor can save the day here.

For the most part I believe basic compression does the job. Optical compressors or compressors with low ratios, low thresholds and soft knees for some more transparent level controls, hard knee, higher ratio,VCAs and FETs for more aggressive control and shaping. Generally speaking.

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