With more consumers than ever listening through less-than-ideal speakers in less-than-ideal environments, dialog clarity is increasingly a major concern for audio post engineers. In this article, Freddy Vinehill-Cliffe from Nugen Audio offers some suggestions for maintaining dialog clarity in a reverb-heavy mix, with specific reference to Nugen’s new reverb plug-in, Paragon.
Nugen Audio Paragon Unveiled
2020 has been an exciting year for new breakthroughs in reverb technology. Back in October, we at Nugen Audio unveiled Paragon, a true convolution reverb, which uses state of the art de-composition and re-synthesis to offer authentic Impulse Responses with never before seen levels of flexibility. A few weeks before that, iZotope announced their Neoverb “smart” reverb, geared more towards music production than audio post.
Reverb Offers A Sense Of Space
Reverb is certainly one of the most common methods for bringing a sense of space, atmosphere or excitement to a mix, but things might become more complicated when we consider another of the audio post industry’s recent preoccupations: dialog, or more specifically, dialog clarity. With the advent of streaming, and consumers listening through less-than-ideal speakers in less-than-ideal environments, it is arguably more important than ever to consider the dialog clarity in a mix. So important to some, in fact, that since 2018 Netflix’s Sound Mix Specifications & Best Practices document has used a dialog-gated value rather than an integrated value for its loudness target, alongside restrictions on LRA (loudness range) and dialog-gated LRA. So then, how do we incorporate reverb into a mix - an effect that, by definition, makes audio less clearly defined - without disrupting the clarity and consistency of our dialog?
Realistic Or Real Life?
In real life, of course, sound reverberates in all directions, so if an engineer wants to create a realistic sense of space then presumably they should apply reverb indiscriminately across the entire surround field. This is true up to a point; completely dry voices within a beautifully constructed reverb-filled audio space would sound confusing and out of place, but there are ways of ‘situating’ centre-channel dialog in a created world without losing out on important transient detail. The ideal situation is a centre channel with only subtle reverb - or perhaps no reverb at all in an especially busy mix - but where the dry dialog is still sent to more prominent reverb effects in the rest of the surround field. You could, perhaps, use some clever routing of buses to send the dry dialog to your surround reverb channels, and bypass centre reverb altogether. You could control the clarity for each channel by using several different reverb plug-ins, each with a different size and decay time - one for the centre channel, and for each stereo pair across the surround field. Mixing in 7.1.2 that would be one mono reverb and four stereo reverbs in total.
Now, here’s where I try to sell you something.
Paragon - All In One Reverb For Immersive Audio
This same logic can be applied to practically any combination of reverb plug-ins, but Paragon essentially has these functions built-in, all within one instance of one plug-in. The ‘crosstalk’ parameter controls the amount of cross-pollination between each reverb channel. A global crosstalk slider on the main GUI controls the overall percentage for crosstalk between all channels, and below that there are simple on/off controls for crosstalk ‘in’ and crosstalk ‘out’ for the centre channel, the LFE channel, and the sides. Simply put, crosstalk ‘in’ controls how much of the dry audio from other channels is allowed into each reverb channel, and crosstalk ‘out’ controls how much dry audio is sent to other reverb channels.
By default, crosstalk ‘in’ is disabled for the centre channel, and crosstalk ‘out’ is enabled - this means that dialog in the centre channel is sent to reverb in all surround channels, but the centre channel reverb does not receive any dry audio from other channels. Effectively, this still gives the impression that the centre channel audio is situated in the same surround space as everything else, but without causing the same kind of “blurring” effect, you might encounter with all audio reverberating in all directions.
Beyond these simple controls on the main GUI, Paragon’s I/O panel allows the user to set individual percentages for both crosstalk ‘in’ and ‘out’ for every channel. So even in an unusual mix where dialog might not be panned centre throughout, it is possible to set up any individual channel to send but not receive reverb crosstalk. There are also similar controls to set up individual pre-delay and decay times for each channel.
Tweak The Impulse Response
Further to this, Paragon’s IR panel allows the user to adjust the frequency-specific decay time of reverb Impulse Responses, via an EQ-style interface. With Paragon’s unique re-synthesis method, this gives you the ability to extend or reduce the reverb time for discrete frequency bands, without adjusting the amplitude of those frequencies, and without affecting the reverb time of other frequencies or disrupting the innate character of the Impulse Response. With this feature, you could improve dialog clarity even further by reducing the decay time specifically for fundamental frequencies where dialog sits, without reducing the decay time for other frequencies. You could even compensate for the shorter decay time in some frequency bands by extending the decay time in other bands.
For more NUGEN-specific tips and tricks, please check out the Nugen Audio YouTube channel or the Learning section on the Nugen Audio website.
Not Got Paragon?
If you don’t own Paragon yet, no problem, Paragon, along with all other NUGEN Audio plug-ins, has a free, 15-day, fully-featured trial.