|Vol. 28 Issue 2 Reviews||Reviews > Products >|
|Altiverb Reverberation Software|
Audio Ease, Lagenoord 26, 3513 GW Utrecht, The Netherlands; telephone (+31) 30-2433-606; fax (+31) 30-2438-500; electronic mail email@example.com; World Wide Web audioease.com/Pages/Altiverb/AltiverbMain.html
Reviewed by Michael Theodore
There is no shortage of reverberation plug-ins currently available, and most of them are based on algorithmic simulations of naturally occurring reverberation (based on delay lines, all-pass filters, etc.). There is, however, an alternative approach, which produces more “natural” results. This second approach is called convolution, and is not based on simulation, but rather on a kind of sampling of the acoustical properties of a real place. Either a starter pistol is fired, or a sine wave is swept across a broad range of frequencies, and a recording is made of the results. This recording is called an “impulse response.” Convolution based reverberation convolves (which is to say, multiplies in the frequency domain) an impulse response with whatever sound source is to be reverberated. In principle, the results should be essentially the same as a recording made in the exact location where the impulse response was recorded. Audio Ease Altiverb is a great sounding, powerful, easy-to-use reverberation plug-in which is based on convolution. It operates on the Macintosh platform only, and functions in MAS, HTDM, RTAS and VST hosts, supporting mono, stereo, and quad output.
The user interface is quite simple (see Figure 1). Like most plug-ins these days, the design emulates a rack-mount device. The controls on the interface are few, and are easy to understand. The actual impulse response is selected from a drop-down menu in the middle of the unit. Altiverb ships with a number of excellent impulse responses, sampled from such places as the acoustically outstanding Concertgebouw in Amsterdam. In addition, there are plenty more impulse responses available at the Audio Ease Web site, including many produced by users. The interface displays a picture of the recording location, and also contains information about the gear used in the recording.
The largest knob on the interface is devoted to the actual reverberation time. A setting of 100 percent lasts the length of the original impulse response. Anything less than 100 percent puts a decaying envelope on the original impulse response. Changing the settings on this knob require some “thought” on Altiverb’s part, and it may take a few seconds to compute the new value. There are also knobs for the wet and dry components of the mix (which function exactly how one would expect), as well as a pre-delay knob (which allows one to the delay either the wet or the dry signal).
The only other element of the interface is a set of two buttons letting the user choose between “No latency, high processor load” and “High latency, low processor load.” Altiverb is highly processor intensive. I tested it in several VST hosts on both a 400 and a 500 MHz G4. In both cases, it was very easy to bring the computer to a screeching halt (especially when using long reverb times). However, this was only the case when using the no latency mode. The problem simply went away when using the high latency mode. The catch is that the resultant audio will no longer be in sync with your original source material. This is not actually a big problem, as the Altiverb interace tells the user exactly how much latency there is, and one can simply move the track so that it is exactly back in sync. However, some users may find that this breaks the flow when one is in the middle of composing or mixing. Therefore, while you can get away with a 400 MHz machine, you’ll be considerably happier with a faster machine (the fastest possible). These remarks apply even more if you are using the quad outputs of Altiverb!
Issues of computing power aside, Altiverb is a joy to listen to. The reverberation it provides is warm, spacious, and absolutely convincing (given an excellent impulse response). I tested it in on many sources, including all manner of acoustic instruments, voices, and various synthetic textures with a large distribution of frequencies. The results were excellent with all of these sources—it soon became my favorite reverb. (My one complaint about the excellent factory presets is that many of them sound ever so slightly “mid-rangey,” although this is easily addressed with judicious equalization.) However, there are still situations where an algorithmic-based reverberation unit would be useful. Even though the reverberation output from such a unit is comparatively “unnatural,” this may be a desired effect. Natural or not, there are certain classic reverberation sounds that are created algorithmically. In addition, an old school reverb unit has much more flexibility with respect to shaping the timbral qualities of the sound. With Altiverb, absolutely everything depends on the quality and character of the impulse response. However, it’s important to note that one can use the IR Pre-Processor application that ships with Altiverb to create one’s own impulse responses. You can go out and record any space that you have access to and bring the location to your desktop. One could also shoot an impulse through an expensive algorithmic reverberation unit and record the impulse response from there.
There are other “sampled acoustics” processors on the market. Sonic Foundry’s “Acoustic Mirror” has been around for years (PC only), Bias Peak 4 now comes with its own “ImpulseVerb,” and Emagic is on the verge of releasing a similar product called “Space Designer” (Macintosh only). Whatever the merits of the competition, when it comes to quality of factory impulse responses, clarity of user interface and sheer quality of sound, Altiverb is clearly a winner.
The HTDM version of Altiverb (for use with Digidesign
hardware) is listed for US$ 795.00. The MAS/RTAS/VST/AudioUnit version
is listed for US$ 495.00. A CD-ROM loaded with further Impulse Responses
is available, in addition to the collection of free downloads on the Audio
Ease Web site, for US$ 29.95.