Mixing Revealed  
Surround Reverbs for Pro Tools
By Rich Tozzoli

Surround sound is everywhere. From million-selling music DVDs to video games to television broadcasts, surround sound is an explosive field. And Pro Tools is one of the most powerful platforms for mixing multi-channel material. So let’s take a peek at some reverb plug-ins that can help push your mixes way beyond stereo.

When I first began mixing in surround, none of these plug-ins existed. Mixing engineers had to improvise, using a combination of stereo and mono reverbs, placed discretely with panners to create a “surround effect.” With the advance of time and technology, Pro Tools mixers now have the option of using reverb plug-ins created expressly for the purpose of multi-channel mixing. How lucky we are!

Digidesign’s ReVibe is a top plug-in choice for surround mixers.
The Digidesign ReVibe reverb plug-in works in mono, stereo, or surround (LCR, LCRS, Quad, 5.0, 5.1), and features a complete set of room modeling controls. Designed to take advantage of the new DSP chips on the Pro Tools|HD Accel card, ReVibe is often considered the big brother of the very capable Reverb One.

ReVibe has more than 200 presets and can run at sampling rates up to 96kHz. A true room-modeling reverb, users can choose from a nice variety of sound types, from arenas and cathedrals to vintage digital, film, post, and other effects. To tweak the presets, you can blend room characteristics and colorations along with early reflections and equalization.

ReVibe has separate level controls for input, front, center, rear reverb, and rear ER (early reflections). The room coloration selector features separate HF and LF color sections, and the reverb section gives you control over type, level, time, pre-delay, diffusion, attack shape and time, rear shape, size, and spread. There’s also a decay color and EQ section with an equalization GUI and a contour GUI.

For surround mixers, all of this control means you can place your elements in a huge variety of environments, with extensive tonal control. On drums, I like to send the overhead mics to a Quad Lexicon 300 in the “Vintage Digital” folder and carefully adjust the rear reverb and rear ER settings to create a lush, full-sounding kit. When using ReVibe on a vocal (try the “Short Vocal Spread” preset in the “Plate” folder), it’s nice to have separate center control, which allows me to have a little (or a lot) of ’verb in that channel. I can grab the EQ points directly on the graphic interface and adjust them quickly on the fly, without any “zipper” noise.

ReVibe’s true strength is its flexibility — I use it in some fashion on virtually every surround mix I do.

Altiverb 5 is an example of a parametric convolution reverb.
Altiverb 5
Altiverb, from Audio Ease, is a parametric convolution reverb plug-in. Convolution is the process of replacing samples with scaled impulse responses (IRs) — actual recordings of hardware units, spaces, or environments.

The Audio Ease team has traveled the globe to capture some amazing impulse responses for Pro Tools users to explore. And many of those impulse responses are in surround. Check out the Castle de Haar Ballroom, Konzerthaus Vienna Large Hall (Center to Far Quad), Clubhouse Studios, Mechanics Hall, and Sydney Opera House. If you happen to love the sound of your apartment’s stairwell, you can even capture it yourself and add it to your Altiverb collection with the included impulse response pre-processor software.

Altiverb 5 features a handful of new impulse responses, additional flexibility, and improved CPU drawing capabilities. It even features a CPU meter displaying how much of the computer’s processor is being used for calculations. Altiverb provides four bands of EQ, including bass and treble Baxandall EQ, as well as three-band damping. It also gives you control over reverb time and size, reflection gain and delay, tail gain, tail delay, and more. You can even change where your source audio appears on stage, and trigger some cool test sounds to check your selected reverb — something I find myself using constantly.

Altiverb is designed for the Mac OS X platform and works with HTDM, RTAS, MAS, VST, and AU plug-in formats. Check it out for yourself at www.audioease.com, and download a few of those new impulse responses.

The Waves IR360 reverb plug-in is specially designed
for surround mixing.
Waves Surround Tools
Waves offers several reverb options for surround. The Waves R360 is a warm-sounding 5.1/5.0 reverb that creates reverb tails only. It includes controls for the reverb “sound” and “mix” properties, and is specifically designed for multi-channel production. To generate early reflections, use the S360 Surround Imager, which is included in the 360 Surround Tools package.

The new IR360 Surround Parametric Convolution Reverb is an impulse response reverb, capable of up to five-channel sound field processing. The IR360 has extensive capabilities, and includes a four-band paragraphic EQ (based on the Renaissance EQ), 96kHz support, and full control over parameters such as size, RT60, density, resonance, decorrelation, damping, and CPU usage. As with Altiverb 5, users can capture additional impulse responses from their own spaces or devices. There’s also a large library of multi-channel impulse responses available at www.acoustics.net. Some of my top picks in this collection include Masterphonics Studios: The Stone Room, Trinity Church NYC, Teatro Valli Opera House (Row 6), and Azrieli Hall. The five channel output meters help you keep tabs on the action and are controllable with the front/rear balance.

The TL Space impulse response reverb plug-in has virtually
zero latency.
Trillium Lane Labs TL Space
TL Space is cool because it’s a mono, stereo, and multi-channel convolution reverb that runs on TDM chips. Not only does it lighten the processing load on slower computers, it also provides virtually zero-latency operation. On the downloads page of TL Space website, www.tllabs.com, you can grab some additional tasty multi-channel impulse responses. Some of my favorites: Hanzehof Concert Hall in Zutphen, The Netherlands; Rhoon Church in Rotterdam; and Trillium Lane’s own studio in Washington. And even though it’s not surround, try sending a kick drum into the “Vacuum Cleaner Tube” impulse response — it’s waaaaay cool. TL Space will load most impulse responses, so you can also take advantage of some of the public domain sounds available on other websites.

All three of the impulse response reverbs mentioned above also allow for sample reversal, which can create some amazing effects. Try a short one on a drum loop timed to the tempo of the tune.

I’ve been using multi-channel convolution reverbs for quite some time, beginning with Sony’s DRE-S777 hardware unit and followed by the first Altiverb plug-in, which was released several years ago. I’m drawn to the fact that you can place instruments in actual acoustic spaces or route them through virtual versions of some top-notch hardware reverbs. Artists I work with often notice the depth and beauty a good impulse response reverb can bring to their music, which makes me look good in the process!

In surround, the results are even more dramatic than in stereo, as the sense of depth and width are increased. Many, if not most, of the spatial impulse responses were actually captured for the purpose of multi-channel use. So if you’re tired of the same old sound, set your rig up for surround and put some of these reverbs to the test. Your ears will thank you!