Audio Ease uses Apple�s processing power to provide cost-effective surround reverbs.
Altiverb V1.1 from Audio Ease in the Netherlands is a sampled acoustic reverb plug-in for Digital Performer and MAS applications. Offering mono, stereo, and 4-channel samples of real halls, churches, forests, and other acoustic environments, it brings a new level of software-based reverb power directly to your desktop.
As we all know, sampled acoustic processing takes enormous amounts of DSP power to operate. Altiverb is the first native reverb plug-in to utilize Altivec, the remarkably fast Velocity Engine co-processor that lives in Apple Power Macintosh G4 computers. Use of this processing power offers real reverbs with lengths up to 40 seconds (not that you�ll need one that long). The one drawback of this power is that CPU usage can be substantial, but each new G4 upgrade offers better plug-in performance.
Altiverb presets are called �impulse responses,� and are created by firing a starter pistol or playing a sine wave sweep from a speaker in an acoustic space. Like other sampling reverbs, the resulting reverberation decay is recorded as a digital audio file. Using a process called deconvolution, the dry source signal is literally extracted from this audio file, leaving behind an exact acoustic representation of the space.
Altiverb provides several different mono-to-mono, mono-to-stereo, stereo-to-stereo, mono-to-quad, and stereo-to-quad presets. Samples such as Utrecht Conservatory, Concertgebouw, and Vredenburg Concert Hall have been included. The files are loaded in upon installation (via CD-ROM) and stored in a folder called Altiverb Impulse Responses. In addition to the prerecorded samples, an Impulse Response Pre-Processor is included, allowing users to capture their own sounds. Besides the ability to sample your favorite local church, this feature offers the potential to record your favorite non-time-variant digital reverb preset or plate/spring reverbs.
The user interface for Altiverb is quite simple. Upon opening the plug-in, you are presented the graphic seen in the photo. The large knob on the left adjusts the length of the decay, which is indicated numerically. Sampled reverbs can only be shortened, and the program has to calculate the new decay shape when altered. A red light will flash in the knob�s indicator when computing, and will turn green again when finished. When set to 100 percent, you hear the reverb generated by the entire impulse response. Changes are made by entering a numeric value or by simply clicking and dragging.When choosing a reverb with four channels (as I hope you all will), you use the Output 3 & 4 selector next to the RT knob. Next to that is the actual impulse response selector. The presets are dependent upon the contents of the Altiverb Impulse Response folder, and appear via a pop-up menu. The Wet Knob controls the wet signal strength and can be turned down to �144 dB, which is silence in the 24-bit domain. The Dry Knob adds dry signal, and both knobs are at 0 dB in the 12 o�clock position. Predelay is also available, and turning the Predelay knob to the left delays the dry sound, whereas turning it to the right delays the wet sound.
The latency selector offers two modes. The �high latency� mode uses a minimum of processing power, but produces longer delays between input and output. Version 1.1 of Altiverb offers better performance than V.1.0 in this mode, and is available on the company�s Web site. �No latency� mode offers no delay between input and output, but at the expense of increased processing power demand. This is where newer Macs will offer better performance. Altiverb offers a unique graphic for each preset, as seen on the right of the plug-in. This Monitor can display a variety of data such as various photographs of the environment, a Layout Picture with mic positions and speakers, Recording Statistics such as mics and playback info, actual Impulse Response Stats such as sample rate and length, or Onscreen Help. The help section is accessed by simply clicking on the question mark in the graphic, and will display information about the controls when you roll over them with your mouse. Altiverb can display graphics for each preset via JPEG, GIF, PICT, or TIFF files. When working with a 44.1 kHz session, Altiverb uses BarbaBatch�s sample-rate conversion technology to resample the impulse responses to the rate of the song. All included IR�s are 48 kHz standard, and the only limitation of working at 44.1 kHz is that preset switching is a fraction of a second slower. Note that the company has taken great care to make sure that the quality of the sample change result does not suffer. Users could choose to sample rate convert every setting, but by letting Altiverb handle it on the fly, the download size and hard disk space needs are reduced considerably.
Altiverb and its downloadable demo are available at www.audioease.com. The Audio Ease online store price is $495.