Comparison Processing

Comparison shopping at the AES convention or over the web has recently become even more complicated. For some of us, that is because the number of flexible comprehensive DSP units available will double this year. These devices are in a unique category of audio processing, as they allow the same flexibility in signal path and processing function as an empty equipment rack; a roll of cable; and warehouse of audio processors. Unlike their analogue counterparts, these flexible DSP units are difficult to compare. There is no current metric for accurately gauging the equivalent size of the equipment rack, the (virtual) wiring time required or the size of the processor inventory.

There are a wide variety of the fixed-format signal processors for sound reinforcement applications. While some of these approach the capabilities of the flexible DSP units I am discussing, they are distinct from them, in that they have a fixed set of signal path routes, fewer audio components (such as no mic mixers), or limited variation in the order of the processing. There is a significant tradeoff in cost and setup complexity between the more defined processors and the flexible units. Specialized training is highly recommended before implementing the highly flexible devices.

There are only a few of the flexible and comprehensive DSP units available, starting with IED (Innovative Electronic Designs) UDAPs; then Peavey MediaMatrix; BSS Soundweb, IED 3200; Yamaha DME32; Symetrix Symnet; and the Biamp Audia. Peak Audio developed the visual interface now common in these devices, using a schematic drawing metaphor for the design interface, and Peavey had the vision to implement it first in the MediaMatrix. Basically, the system designer draws out a schematic signal flow, selecting processing devices from a menu, as required.

While a common metaphor is used in all of these processors to design the signal processing, the capability and cost-effect of using one unit compared to another is not necessarily obvious. If you must substitute one unit with another from a different manufacturer, then you will need to evaluate a number of issues and capabilities. Here are a few of the questions that arise when evaluating the alternatives. What is the input and output limitations for the unit? Can multiple interfaces be connected? If so, are you adding DSP power with each input? Do you need more DSP power for each input or is it concentrated in one area of the processing path, leaving other paths with unused DSP? If the DSP is not added in lock-step with input quantity, when will you run out of DSP support for the input quantity? Does the unit provide adequate remote control capability? Does it support your control format? Can this control be routed to the internal process you want to control?

Then there is the question of how to compare the features and functions of the processing modules within the device. It was easier to compare the specs of the analogue devices, because they had a long history of providing (almost) standardized specifications, and the front-panel controls all had to fit into a 19” rack. Their DSP counterparts are more difficult to measure and quantify. The control surface is now a feature that can be changed with software revisions and is not limited to a physical size. The result can include extreme control ranges and a vast array of parameters, that isn’t required in every application. You must carefully define your needs prior to making the comparison.

There is also a significant difference in the user interface features of the design software used to develop the signal processing you need. While all of the software shares the CAD-like schematic interface, not all have the same drawing, DSP resource management or troubleshooting tool sets. However, these differences will depend on your own preferences for drawing the signal flow; access to the processing hardware; and the complexity of your processing requirements.

The manufacturers will often quote MIPS to quantify the DSP processing power, but this does not directly translate into usable audio capabilities. The style and efficiency of the code can allow units with lesser processing to equal or exceed those with more horsepower. The architecture of the units will also influence this component. The ability to network devices together, and allocate the audio processing across the network, can extend the capabilities of some processors. However, issues of latency, bus allocation and distance limitations will need to be considered.

These super-processors that contain an entire sound system in a box, and can pull a warehouse of processing into play at the click of the designer’s mouse, have created a massive change in the way sound systems are built. The increasing range of choice in manufacturers and models of processors will lead us to new ways to quantify these devices. Comparison shopping will never be the same.

United Entertainment Media Inc.
460 Park Avenue South, 9th Floor
New York, NY, 10016
Ph. 212-378-0400
FAX 212-378-2160
by e-mail

page construction