Combining Reverb with Other Effects

This is an excerpt from Kim Lajoie’s guide, ‘Using Reverb in the Mix’, available on his blog for composers, producers and audio engineers. 

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Even the basic reverb processors provide a great deal of tonal variety and a broad range of ambience possibilities. These possibilities expand enormously when you consider using two or more reverbs in a mix. If you want to push your reverb even further though, you should consider combining your revert z        zb in series with other effects. This is often easy with plugins and many hardware reverb processors offer multiple ‘engines’, where one engine can be configured for reverb and the other can be set to another kind of effect.

Usually when reverb is combined with other effects, it is done in series. That is, the reverb and the other effect form a chain (either effect->reverb or reverb->effect). This chain is used in place of a single reverb processor in a mix.

EQ

EQ is the most common and useful effect that is paired with reverb. In fact, it is so common that many reverb processors include some basic EQ that is accessible right alongside the reverb adjustments. This usually takes the form of high and low cut filters, and sometimes shelving filters. While most reverb processors include some basic onboard EQ, having a more sophisticated EQ on hand can greatly open up the tonal possibilities.

Generally, you can approach EQing reverb as three bands:

Lows: Reduce or cut the lows to cut down on mud and boom. This can sometimes really help clean up a mix and is often useful when the mix needs to have a precise and clear sound. The reverb processor’s onboard low-cut filter can sometimes be too blunt if you need to reduce the lows, but not eliminate them entirely. A shelf or broad bell shape will give you more control and power to shape the sound of the reverb. On the other hand, increasing the lows is sometimes useful for heavy dark ambience (especially unnatural-sounding ambience) and for special effects. Try running a kick drum through a low-heavy reverb…

Mids: Reducing the mids of a reverb can thin it out, sometimes helping it fit in the mix. It can also help give you a very “hi-fi” sound. This can be useful after you’re happy with the general shape and sound of a reverb, but find it is reducing the clarity of the lead vocal. On the other hand, boosting the mids a little can increase thickness and body in the reverb. This can be useful for bringing the reverb a little more forward in the mix without changing the overall balance too much.

Highs: Reducing the highs can go a long way to cleaning up sibilance in vocals (“s” and “t”) if the reverb is catching too much of it. Reducing or cutting the highs can also make the reverb become less noticeable overall, which may sometimes help it sit better in the mix. Boosting the highs can work well when you want to emphasize the reverb and make it more noticeable without muddying the mix.

It doesn’t matter which order you use the EQ and reverb (either EQ->reverb or reverb->EQ), because they’re both gain-linear. That means they behave the same way for quiet signals as they do for loud signals. For hardware workflows, you already have a capable EQ available if you return your reverb to a regular mixing desk channel instead of a stripped back aux return or stereo input channel. For DAWs, your effects bus should allow you to insert the EQ plugin of your choice directly before or after the reverb plugin.

Delay

Delay is also so commonly used that a basic delay is included in almost every reverb processor in the form of pre-delay. This places a short 100% wet delay with no feedback in series with the reverb engine, so that the whole reverb tail is shifted back in time. But that’s just scratching the surface of what you can do with delay.

With more sophisticated delays, you can create multiple copies of the reverb tail. This is particularly useful for making a lackluster reverb sound more dense and lush. This is especially effective when the delay taps or echoes are panned (for example, with a ping-pong delay). Delays that get darker as they feedback can extend the reverb tail in a very natural-sounding way.

Generally, the order of the processors doesn’t matter (delay->reverb or reverb->delay) because delay is usually gain-linear. Having said that, weird and interesting things can happen if you use a delay with some non-linear process in the feedback path (such as tape-style saturation). For these situations, the order does matter, and you’ll have to decide whether you add a clean reverb to the saturated delays, or you saturated the delayed reverb tail. Try it both ways and listen to the difference.

Compression

Unlike EQ and (most) delays, compression is definitely not gain-linear. That means it behaves differently depending on the level of the input sound. For this reason, the order of processors (compression->reverb vs. reverb->compression) makes a significant difference in sound.

It might be helpful to look at this as a choice between “reverbing the compression” (sound->compressor->reverb) or “compressing the reverb” (sound->reverb->compressor).

If you add the reverb after compression, the result will be close to the regular conventional sound of the reverb. The difference will be that the reverb will not respond (as strongly) to the dynamics in the source sound. This will be most noticeable with a very dynamic recording where the dry sound remains quite dynamic, but the signal sent to the reverb is strongly compressed. This will mean that the quieter sections will be quite wet, whereas the louder sections will be drier (because the compressor automatically turns down the louder audio going into the reverb). This approach can be useful if the reverb is ‘catching’ louder phrases or sections in a distracting way. It might be interesting to experiment with parallel processing here – perhaps to have a longer brighter reverb fed by a heavily compressed version of a vocal, combined with a shorter darker reverb fed by an uncompressed version of the vocal.

By doing it the other way – “compressing the reverb”, you are directly altering the dynamic response of the reverb itself. This is not a common process, but may be useful for achieving special effects or unnatural ambiences. For example, smooth deep compression on a long reverb tail may lengthen the reverb tail or make it sound “deeper”. More aggressive compression can create a very unnatural pumping effect that emphasizes the reverb without washing out the original sound.

De-essing

De-essing is sometimes used with reverb as a kind of automated tone control. It can be useful if your vocal needs a relatively bright reverb, but the reverb is ‘catching’ the sibilance in a distracting way. By using a de-esser->reverb chain, the signal being sent to the reverb will have the sibilance turned down, meaning they’ll be much drier and less distracting. Because the signal coming out of the de-esser is being processed 100% wet, you can actually get away with a lot heavier de-easing than you normally would when processing the main vocal channel. In turn, this allows you to use a brighter reverb than would otherwise work in the mix.

Like compression, de-essing is not gain-linear. Because of the way it works, it’s most effective to set up a dedicated chain for processing a vocal channel. This way, other instruments won’t interfere with the sibilance detection of the de-esser. It’s also important to consider the order of the processors. The most natural sound will usually be produced by a de-esser->reverb chain, where the de-esser works on the dry vocal sound and the reverb processes the de-essed sound. If, on the other hand, you use a reverb->de-esser chain, the de-esser will actually be processing the reverb tail, not the dry vocal. This will result in an unnatural modification of the decay of the reverb, which may be interesting for special effects.

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Chorus / detuning

Like delays, chorus and detuning processors are useful for thickening the reverb tail and making lackluster reverb processors sound more dense and lush. Unlike delays, the order of using chorus/detuning with reverb matters. Using a chorus/detune->reverb chain will result in a thick sound with a regular reverb tail. On the other hand, using a reverb->chorus/detune chain will result in a much more ‘processed’ sound because the reverb tail itself is being modified.

Overall, combining chorus or detuning with reverb tends to thicken the reverb in an unnatural way. Stay away from this approach if you’re mixing live performances, but feel free to experiment if your sound tends toward the electronic and unreal. ◊