About The Nebula Plug-in

Nebula serves as an excellent example of a true "best of both worlds" in using high end hardware and using plug-ins for working with audio files. Historically, mastering has required very expensive outboard hardware in order to edit recordings without noticeable degredation, using digital sound as a means of preservation and working in a clean, unobtrusive environment. Until recently, it seems that most software has been secondary in doing the tasks involved in mastering except for the indexing and final CD creation process.

With a newly developed program called "Nebula", by Acustica Audio (Acustica-Audio.com), the differences between digital and analog are coming together very quickly to bring a new way to master with all the benefits of both worlds. To appreciate what this program is working to achieve, it is helpful to look at what has led up to the current technology.

It has long been said that mixing "inside the box", or within the confines of the computer, could simply not compare to having the traditional hardware used in mixing and mastering. The division has been that the hardware is typically very expensive, and has a history of making the recording studio and mastering house an elite-club. For years, the home recordist has seen the prices come down on mixing consoles, recording devices, and consumer-level hardware, to a point where just about anyone had a level at which they could record themselves with a very good quality.

As digital technology continued to bcome more and more affordable, and computers got faster and faster, the market for bringing all the elements of a studio together into software programs became a huge new industry. From sequencing to notation, multi-track recording and mixing, to mastering, and even video editing, the modern studio can practically be carried around on a laptop with few limitations.

The draw back to the seemingly ideal digital studio, is that it is very hard for even the finest digital equipment to compete with the quality, musicality, character, and natural sound of high end analog gear. Where digital processing can excel at precise measurements, non-destructive editing, and very linear changes to sound, analog equipment has very complex elements of sound processing that tends to have more pleasant side effects than negative ones. Plugins that emulate such hardware have gained a great popularity, some doing a better job than others, and very few offerings that really restore what is done best with analog processing.

A Convoluted Theory

Several new technologies that have been improving on the process of emulating high end equipment are centered around what is called "convolution". The convolution process involves sending a test tone signal through a source sound, and processing the outcome of that signal. The resulting file is called an Impulse Response, or IR. It has been popularized by capturing the essence of live acoustic environments, making for incredibly detailed reverberation completely within the digital realm. Convolution can also take a virtual snapshot of frequency changes as they relate to the original volume of a signal, making it possible to gather a very basic, but often very realistic digital recreation of hardware equalizers.

The convolution process has been broadened into what is called dynamic convolution, where many settings are sampled and pieced together similar to snapshots being threaded together to make a moving picture. This technology has made for very convincing emulations of high quality equalizers, but also takes a great deal of processing power, and is protected by a patent that obstructs sharing the technology.

There are many benefits to this technology, among them being the use and popularity of digital 'samples' of very expensive gear that were unattainable to many home-recordists and hobbyists until the advent of the technology. However, many limitations found in the technology have continued to limit the consideration of widely adopting the technology into practice for mastering. Details of the interaction of phase coherency, the actual speed of dynamic information in impulse samples, filtering and deconvolving processes, not to mention the quality of source-sampling and equipment used, are all issues that may not hinder individual tracks in a mix as much as a final stereo mix of complex, multi-instrument program material. In some aspects, the elimination of certain distortion and other harmonic content from equalization curves can be a benefit, if properly aligned at very precisely aligned settings. But, even the slightest changes from sampling the original devices can make impulses unusable for a finished mix.

Nebula Background

Vectorial Volterra Kernels Technology
(Pizza, Mandolins, and the Genius of Simplicity)

Then comes "Nebula". The creator of the Nebula engine is Giancarlo del Sordo. His initial efforts were born out of the desire to eliminate some of the negative artefacts created by current convolution technology. Along with a few friends, Giancarlo was able to develop some results that seemed to maintain the integrity of the orignal signal being sampled much more succesfully than what had been done before. Giancarlo, along with the help of Francesco, Graziano, Antonello, and Mirco began to gather together to form Acustica Audio, enlisting a community of Beta Testers for debugging, testing, suggesting, and adding to the hardware being sampled. According to Giancarlo, the essence of a determination to do what had not been done, was a quality indicative of the Italian spirit. In seeking solutions to very complex issues dealing with improving on the concepts of convolution and dynamic convolution and developing a sampling process different from both concepts, the Acustica Audio team were able to create a processor capable of dealing with these issues in a brilliantly simple, elegant manner.

The current capabilities of this program reflect a major step forward in using digital processes to simulate those of it's analog sibling. By creating streams of information about the source's harmonic distortion, dynamic changes, and frequency curves in real time, "Nebula" is able to recreate a very real digital impression of analog hardware in real time. Where convolution can create a very precise single picture of a devices setting, Nebula is able to sample streams of information working side by side, and with enough resolution to be very convincing. Beyond the realism of the process lies other benefits, in that the unwanted side effects of the hardware being sampled can be altered and optimized, thus bringing us lower noise floors, increased dynamic range, and even the ability to gain one feature at the absence of another. We can use a tape machine in "clean mode" without imparting the analog harmonic distortion the signal would carry. We can process the benefits of the same device with harmonic distortion but without a change in frequency curves. The benefits of this technology are simply stunning.