Audio Ease, the first manufacturer to release a real-time convolution-reverb plug-in, started the convolution revolution in earnest with Altiverb. Initially available as a plug-in for only MOTU Digital Performer, Altiverb leveraged the Mac's Altivec vector-processing engine to produce very dense and realistic reverb. I reviewed version 1.4 of Altiverb in the May 2002 issue of EM and was quite impressed by its sound and its staggering processor demand.
FIG. 1: This figure shows a waterfall display in the IR view and mic positioning in the Info window. It also shows Damping & Gains parameters.
Audio Ease has introduced Altiverb 5, a major upgrade that maintains the reverb's outstanding sound quality, adds a raft of new features, and has an extensive collection of impulse responses. Altiverb 5 remains for Mac only, but it's available in HTDM, VST, MAS, RTAS, Audio Units, and AudioSuite formats. Like most professional audio software, it is copy protected, but you can choose either iLok or challenge-response authorization.
Now with Parameters
Altiverb's most significant addition is variable parameters. The variable parameters available in Altiverb 1.4 were the reverb decay time, which could only be shortened; predelay time; and wet- and dry-level controls. By version 4, Altiverb had added only basic bass and treble EQ. After Altiverb 4's release, however, Waves introduced IR-1, a convolution reverb with variable parameters. Altiverb 5 is Audio Ease's answer to IR-1, and it's a substantial one.
Altiverb 5's user interface maintains the basic look of the original interface. It has the large virtual knob for decay time as well as the Info window, which shows photos of the space being emulated and an illustration of where the microphones were placed when the impulse response was captured (see Fig. 1). Altiverb 5 adds a drop-down menu for presets, buttons that trigger internal test sounds, a size control, and more-extensive level controls. There's also a parameter-adjustment area, a snapshot section (added in version 4), and enhanced displays.
FIG. 2: The Info window shows a photo of the space in which the impulse response was recorded. Note the illustration of the stage positioning at the bottom of the screen.
The display section is now divided into the IR view and the Info area. The IR view has input and output metering and shows either a rotatable waterfall display representing the reverb characteristics or a multichannel display that shows the decay per output channel. In the Info area, you can cycle through screens that show the placement of sources and microphones, photos of the space, recording information, and a rotating virtual-reality movie of the space (see Fig. 2).
The parameter section has four pages — Damping & Gains, Stage Positions, EQ, and CPU — which you access using the radio buttons to the left of the parameter controls. Damping & Gains offers three bands of damping and gain controls for Direct Sound, Early Reflections, and Reverb Tail.
The Stage Positions feature resulted from research conducted by Audio Ease on the effect that stage position has on a room's impulse response. That feature allows you to place a virtual source (represented as one or two loudspeakers for mono and stereo sources, respectively) on the soundstage. You can move mono sources left to right and stereo sources closer or farther apart. Front-to-back placement is possible for mono or stereo sources (see Web Clips 1, 2, 3, and 4).
The EQ page has two fully parametric bands and bass and treble shelving EQ, with ±24 dB of gain on each band. A noneditable graphic display shows the resulting curve.
The CPU page has a meter showing how hard Altiverb is hitting the CPU, and it has several settings designed to allow the CPU load to be lightened in some situations. For instance, there is a decay knob that sets the level to which the reverb must decay before it is cut off. That control won't be much help for delicate or exposed material, but in dense mixes the cutoff level can be raised considerably without adversely affecting your audio.
More New Features
Altiverb now accepts multichannel inputs up to 5.1. The reverberator, however, is still only mono or stereo input, so the multichannel input is mixed down and then fed to the reverberator. Although it is always possible to instantiate two stereo Altiverbs for quad input, that still doesn't sound quite the same as a true multichannel input reverb. (The sonic difference could be noticeable for orchestral and post-production applications, but not for most forms of popular music.) Of course, the computational demands with more than two input channels would be huge. The Input/Output gain section changes its configuration with the output configuration, adding pots for multichannel output.
A new snapshot area allows you to capture as many as ten snapshots and recall them manually or through automation. The snapshots are easy to use and are especially useful for post-production applications. Transitions from one snapshot to the next are seamless if they use the same impulse response; if not, the output mutes briefly while changing. Though presets are stored in an Altiverb data folder, snapshots are stored with your DAW session.
You can now use the large decay knob to lengthen and shorten decay time, and the knob has gained a Reverse-Reverb button and a Size pot. The Size pot shifts room modes and affects decay time.
Altiverb comes with several built-in test sources. You can also add your own. The default setting triggers a test sound whenever you finish tweaking a parameter, letting you hear the reverb without having to start playback. That is a useful feature.
A new Presets menu contains applications-oriented presets. You can still go directly to the Impulse Response menu and select one from the large collection of impulse responses.
Hearing Is Believing
I evaluated Altiverb 5 using the same G4/800 MHz Mac that I used for the Altiverb 1.4 review. This time, however, I ran OS 10.3.8 and DP 4.5.2. Though considered a muscle machine when I first reviewed Altiverb, by current standards, this Mac is only a couple of notches above the minimum platform required for Altiverb 5.
Audio Ease significantly reduced Altiverb's CPU demands in version 4, and the difference is noticeable. Instantiating a single stereo-in, stereo-out reverb still made DP's Audio Performance meter jump from about 10 or 15 percent to just under 50 percent, but that's a lot better than when I ran it under version 1.4 on the same machine.
When I added a surround master and inserted a 5.1 Altiverb on it, the Audio Performance monitor started flashing red and green. But the overload light never went on, and Altiverb's CPU meter showed just under 50 percent. You'll need a Power Mac G5 to do real surround work with Altiverb.
Altiverb's sound is still great: very dense, smooth, and spectrally balanced. The EMT 140 emulation is the best plate sound I have heard from any digital reverb. The EQ and damping are useful and provide powerful shaping options. Add the color changes wrought by the Size pot, and it is clear that Altiverb offers tremendous tonal control. You can adjust almost all parameters with little or no interruption in the sound.
On an Impulse
The collection of impulse responses that comes with Altiverb is huge and includes many European churches, auditoriums, and recording studios, as well as a few from New York (see Web Clip 5). There's also a healthy selection of sampled hardware, such as the plate mentioned earlier, the AKG BX20E spring, the Lexicon 480, the EMT 250 digital, and many more. Each of them has a handful of impulse responses, adding up to a very rich assortment. With a convolution reverb, the key to sound quality is well-engineered impulse responses; Audio Ease constantly adds good impulse responses to its site, so you'll always have a large collection of reverb colors to work with.
Altiverb enables you to make and use your own impulse responses, as it has since the program original release. The Altiverb disk includes the Sweep Generator and Altiverb IR Preprocessor, with appropriate instructions, to facilitate the process of creating impulse responses in Altiverb's proprietary file format.
I have only a few minor quibbles: the lack of multichannel inputs is one, but given how difficult convolution is computationally, it might not be practical to expect that feature. Also, none of the parameters are displayed numerically until you click on a knob. Although that arrangement is workable , I prefer being able to take in all of the settings at a glance.
Audio Ease had a winner with the sound of the original release of Altiverb. Now the company has brought the product's features up to the same high level. Audio Ease did an excellent job of choosing parameters that will get used all the time, rather than going for the glitz appeal of things that you would use only occasionally.
Altiverb gives you flexibility and variety, is straightforward to use, and has good presets, all at a reasonable price. The sound of the EQ and damping is superb, and the user interface is designed well. The addition of test sounds and application presets adds useful functionality that will come in handy. The recording information and photos help give a feel for the space.
In short, Altiverb 5 is unquestionably at the top of the digital-reverb heap — a first choice for everything from post-production to jazz or classical, and from rock 'n' roll to hip-hop.
Larry the O's San Francisco — based company, Toys in the Attic, provides a variety of musical and technical services. He is also a contributing editor to EM. As if that weren't enough, he has a day job, too.
convolution reverb software
$895 (adds HTDM)
upgrade from version 4, $169
OVERALL RATING (1 THROUGH 5): 4.5
PROS: Superb sound. Useful selection of parameters. Extensive impulse-response collection. Many powerful new features.
CONS: CPU hit, though improved, is still not to be taken lightly.
Audio Ease www.audioease.com