When it comes to the use of reverb, whether it be for music production or audio post, there are no hard and fast rules. If it sounds as though it works, and you feel that it supports the creative intent of the project, then go for it. Having said that, there are several factors to think about when considering how and when to apply reverb. One such factor is the question of whether to use mono, stereo or surround reverbs. In this article we’ll look at the potential pros and cons of each, and I’ll include examples of my own experiences in applying reverb to dialogue.

Mono

There are several cases in which you may wish to apply mono reverbs to dialogue. One such case is when intercutting lavalier microphones with boom mics. Ideally, you’d stick with the boom wherever possible, but occasionally you’ll need to use the lavs, such as when trying to minimise noises from props, or perhaps when someone is too far off mic from the boom. Cutting between lav and boom mics poses a few challenges, with perhaps the most obvious being the EQ. Before you get to adding any reverb, the tonal balance will need to be adjusted on the lav mics in order to better match it to that of the boom. This is something for another article, but it can either be done manually by ear or using EQ matching tools such as those found in Fabfilter’s Pro Q3 or iZotope’s Dialogue Match plug-ins. Once the EQ is sorted, you’re likely to find that, due to the close proximity of the lav mics to the actors, they pick up audibly less reverb and reflections than the boom. The solution to this is to add just a hint of reverb.

Mono reverbs on lav mics can really help to fit them into the mix more naturally. The goal here is to be fairly subtle and to choose settings which sound as close as possible to the original room acoustic. Some of my personal favourite reverbs to use in audio post are the ones from LiquidSonics and so I’ll be using some of them as examples in this article. In the case of mono reverb on dialogue, I often start with a preset and take it from there. Cinematic Rooms includes a range of very convincing room reverbs, but the ones I find myself using time and again are those which replicate small or medium sized domestic rooms. By keeping this type of reverb mono, you can convincingly place the sound into a scene without it sounding too close up or dry. Often, subtlety really is key. It might be that the reverb is only really apparent when you mute it. Bringing it back should add enough reflections to make the dialogue sound natural within the space, without it sounding like it’s been overdone.

From what we’ve said so far, you can probably also see the benefits of using mono reverbs in this way for ADR. Whether you’re mixing in stereo or surround, a mono dialogue reverb is a useful tool to help the audio from the lavs, along with any ADR, sit convincingly in the scene in a way which blends perfectly with the sound from the boom.

Stereo and LCR

Stereo reverbs on dialogue may be less commonly used than their mono counterparts, but they do have their uses. Once again, there are no absolute rules on this, but there are some things worth trying out. If you have a very wide shot in a scene and a character is talking loudly, or shouting, a stereo reverb can help to open up the sound and give it the width to match the picture. In a stereo mix, this obviously makes a lot of sense, but in a surround mix, stereo reverb on dialogue can make it sound detached from the dialogue if there’s no reverb in the centre channel. A good solution to this is to use an LCR reverb instead. Not all manufacturer’s reverbs support an LCR channel count, but again this is one of the things I like about LiquidSonics. I use three of their plug-ins on a regular basis. As well as the aforementioned Cinematic Rooms, I also use Seventh Heaven, a highly accurate Bricasti M7 simulation, and HD Cart, an emulation of the Lexicon 480L HD expansion cartridge. All of these support the Left, Centre, Right configuration and the benefit of using this on dialogue is that it allows you to go wide with the reverb, while also incorporating some of it into the centre channel but not causing a potential distraction by having it spill into the surrounds. This has uses when you want the sound to remain front focused. I really treat my application of reverb on a project by project basis, but Seventh Heaven is excellent when I want a rich, expansive sound for environments which are perhaps rather more reverberant than typical small to mediums rooms.

Surround

We’ve looked at some examples of when mono, stereo and LCR reverbs can come in handy on dialogue, but what about surround? Well, this is something you have to be a little more careful with. There’s always a risk of going overboard by applying too much reverb, or having it sound disconnected from the dialogue by using settings which just don’t quite match the location depicted on screen. I would say that surround reverbs for dialogue need to be used selectively and applied with care. Typically, I use surround reverbs either for cases where a voice is heard from a distance or off screen towards the back of the room, or when I want to convey a sense of scale to a location. Churches are good examples. I recently worked on a scene where a priest is reciting verses from the bible. It starts with a wide shot, filmed from the back of the church. The priest is stood by the altar at the far end of the church. The mix was 7.1 so this was a prime opportunity to utilise Cinematic Rooms in a surround configuration. Starting with the ‘Large Hall’ preset, I was able to get a great sounding church reverb with just small tweaks to the pre-delay and reverb time settings. On the wide shot, this worked great, but the scene then cuts to a much closer shot. In order to match the reverb to this, I dropped the send level going to the reverb and then, using the Surround Editing Planes feature in Cinematic Rooms, automated the reverb time on the front and centre channel to be slightly shorter to give a sense of a much closer perspective. The ability to do this is one of my favourite features of the plug-in, and it proved to be a great option for that particular scene.

Liquidsonics surround reverbs, which include Cinematic Rooms, Seventh Heaven Professional, Lustrous Plates Surround, Tai Chi and HD Cart, all support channel counts up to 9.1.6 for Dolby Atmos. I’ve used HD Cart recently for a dream sequence where the character experiences some surreal visions. Using the ‘2x Slap+Chorus’ preset in surround, I was able to get the effect I was after.

It’s quite rare that dialogue deviates away from the screen in terms of how it’s panned. Every so often though, I’ll work on a production where the scene warrants it. There was a scene where a number of characters were moving quickly in circles around the main character, chanting and laughing as they did so. It was shot from the perspective of the main character at the centre of the circle, who was stationary as the others moved around him. In this case, the director wanted to create a sense of disorientation with the sound. This was a good excuse to pan the dialogue around the room as the characters moved. One thing to think about, should you ever need to do this, is where the reverb will sit in relation to where the dialogue originates. By this I mean, do you want reverb to be present in all channels, irrespective of the panning of the dialogue, or do you want the reverb to more accurately reflect how the reflections in the room would sound as the sound source moves? Cinematic Rooms has a great feature called Crossfeed. This is a set of controls which let you set the level, delay and rolloff of the crossfeed reverb so that reverb in other channels sound further away or at different levels to the channels closest to the sound. This is a very effective way of simulating how sound propagates in real acoustic spaces, where the reverb responds to the sound’s location in the room. In essence, crossfeed is a form of pan tracking for the reverb. It’s great for sound effects but can be handy on occasions for panned dialogue too.

Final Thoughts

The workflows described above are some of my own suggestions about how reverb can be applied to dialogue using different channel counts. As stated, none of this should be considered a rule or anything which you need to stick to in any way. Rather, they’re things which I’ve find to be effective throughout the course of my own work. I’m a big advocate of Liquidsonics reverbs, so it made sense to use them in my various examples.

I have no doubt that there will be some differences of opinion in what people consider to be effective ways to use reverb on dialogue. Let us know your own preferred workflows in the comments below.