Would You Rather Delay Your Reverbs or Reverb Your Delays?

I am a firm believer that setting up a small reverb, a longer reverb, and a time-synced delay can cover 90% of the mix process. I always set these up as send and return effects within my DAW mixer, because I am old school and it makes the most sense to me. It also makes me limit myself to a couple of virtual spaces, which makes my mixes gel a bit better and sound more natural.
I was working with a class I was teaching and had them setting up their own Pro Tools templates to start this process on their own. I showed them my basic template for beginning a project, which looks like this:

Figure 1: Some audio tracks, some virtual instrument tracks, and a few effects.

One of my students piped up with, “Why do you have sends on your delay aux input?” I had been harping at them about having sends going back to the aux input it was on and the potential for feedback, and he delightedly thought he had caught me in a mistake. When I said it was so I could apply some reverb to my delay returns, the student looked at me like I had two heads.
Let’s take a brief aside and talk about how we use time-based effects in a mix. Reverbs are intended to add a sense of space, but they are also an excellent way to control the front-to-back balance of something in the sound field. If a track has more reverb on it, we tend to perceive it as farther away, and if it has less reverb, then it seems closer. It is the way our brain is used to decoding audio.
Of course, a reverb is just a large collection of delays grouped together until we cannot hear individual echoes, so we can get a similar positioning impact from delays. They give us a sense of placement and depth but with a more distinct wash of sound.
Reverb on Delay
Because delay can become a part of the sound (think of the wash of delays that U2’s Edge uses so often), there are times when it makes sense to put some additional reverb on a delayed signal to push it back a bit farther in the mix. My basic mix philosophy starts with a small room that I run nearly everything in the mix through. While tempo and style will dictate the size of this room, it is typically between 300ms and 500ms of reverb time. I even run a little bit of the kick drum and bass through this small reverb. It just helps put everything in the same space and makes the tracks feel more connected.
I might choose to use this small room to impact the frequency content of the delay signal. I can always use the tonal controls in the delay to roll some of the top and bottom out of the signal, but I may want that energy to help light up the longer reverb should I choose to also route this delay signal to my second reverb.
You can accomplish this effect by putting two plug-ins in line in your DAW, as they almost all process audio sequentially by default. The downside of this is that it is wasteful from a processing standpoint to dedicate a reverb to a track, and you are applying reverb to the entire signal, not just the delay portion of the sound. While this is a subtle distinction, it can make a difference if you are applying it across multiple tracks. Nothing builds up faster than mud in a mix.
Setting up a couple of sends on your delay return in your mixer allows you to apply reverb to just the processed output of your delays. This can make the core sound of your vocal or guitar come to the front of the mix, while everything else sits behind it, giving it a sense of depth.
Delaying Your Reverbs
Nearly every reverb plug-in made has a control called pre-delay. The idea behind this control is exactly what it sounds like, although the words “pre” and “delay” together are an oxymoron. If something is “pre,” it comes before, and if it is “delayed,” then it comes after. Pre-delay, in reference to reverb, means a delay that is used before the reverb starts. In the early days of recording, this was accomplished by sending the Reverb Send to a tape machine as a delay and then sending the output from that to the echo chamber or plate. The purpose was to push the start of the reverb back away from the original start of the audio that was triggering it. The sound at the beginning of the processed audio is complex and fairly nonlinear. Most reverbs refer to these as “early reflections,” and it is the last part of the reverb sound where individual echoes are still discernible.
Because this part of the reverb is so distinctive, having it start at the same time as the signal it is processing can be very distracting and can take away clarity pretty quickly. Pre-delay pushes these reflections back far enough that they don’t get in the way of the signal you are trying to improve with a little reverb. Dream Verb from UA (which comes with all Universal Audio interfaces) does a great job of graphically representing the way pre-delay interacts with the early reflections and wash of diffuse reverb, which are separate portions of the sound of a reverb.

Figure 2: Reflections with almost no delay.

You can see the first yellow line in the reflections box happens almost immediately and will sound as a distinct repetition that is almost on top of my actual signal. This can rob transients of impact and make the signal seem smeared and messy. Applying just a little bit of pre-delay to the reverb allows that first reflection to come in a little later and will considerably clean up the sound.

Figure 3: Even 5ms of pre-delay moves the first reflection out in time and cleans up your sound.

However, when you have spent a lot of time mixing in the box, you get very used to aligning your timing by the tempo of the song you are working on. Delays almost always have a “sync” button to allow you to choose your delay time in musical note values. Reverbs don’t have a way to time align your pre-delay to the tempo of the song, but there is a simple way to address this issue.

Figure 4: The Rob Papen RP-Delay (on the left) precedes the Universal Audio Dreamverb (right).

Simply put a delay plug-in that does have tempo sync above your reverb in the mixer in your DAW. I like Rob Papen’s excellent RP-Delay, but you can use your favorite. Set the delay to a fully wet output, turn on its delay to sync mode, and set it to a quarter-note. I generally try not to use any filtering on this delay plug-in so I get a clean signal going to the input of the reverb. In your reverb plug-in, turn your pre-delay amount as low as possible. Now as you change the tempo of your song, the initial reflection will land on the quarter-note beat no matter what tempo it is at. Please note that this technique is intended for a send and return application of the delay/reverb combination.
Dual Mono Reverbs
Frank Filipetti taught me my favorite reverb trick. It requires a little different approach to routing to your reverb. There are times when the more reverb you add to a mix, the smaller it seems. This seems contradictory, but it comes from having highly correlated material in the left and right channels. This similar material tends to make your mix collapse toward mono.
To minimize this correlation, instead of choosing one stereo reverb, instantiate two MONO reverbs on two different aux returns and pan them hard left and right. Set them to slightly different presets. Then use a single stereo aux send to feed those two aux inputs. Pan the output of your aux the same as the track it is on, or reverse the panning placement for something different. This approach guarantees that the reverb in the left and right channel is similar, but not the same, and it will keep the mix from losing its stereo width. Strange that two mono reverbs would sound more stereo than stereo — but they will. You can see an example of this in Pro Tools with Softube’s TSAR-1 reverb in figure 5.

Figure 5: True dual mono reverb.

There are almost countless delay and reverb plug-ins, so give your Sweetwater Sales Engineer a call at (800) 222-4700 to make sure you find the one that best suits your production needs.
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