Controlling Computers

Sound reinforcement systems are created to offer control to the end users. This control may be a simple as the volume level that is heard by the audience or as complex as systems which can operate automatically to change configurations. The more sophisticated requirements inevitably lead to a computer (or computers) that manage the interaction between components and the status of signals and processing. The computer may control the hardware, but who controls the computer(s)?

In the early part of this decade, Stan Miller sat amid five computers while mixing the Neil Diamond shows. Due to the lack of a standard control protocol, it took that many individual computers to control various aspects of the sound reinforcement system. Stan has always pushed the envelope and this was the price. It took a great deal of organization to maintain that many different applications and computers on the road. It takes even more nerve.

Over the past ten years, significant strides have been made in the digitization of the audio signal within sound reinforcement systems. Once the audio is in the digital domain, exacting control over the switching, mixing and processing of the signal is available. In fact, it should be very easy to handle these details using a computer.

In the late '80s the Louisville, KY company, Innovative Electronic Designs, had developed a control method that would later be adopted (with some contributions from other companies, such as Altec-Lansing) as the AES standard commonly known as PA-422. This offered an inexpensive method to control audio equipment from any manufacturer that was willing to implement the protocol. A number of companies did adopt this control format but far more decided they needed something more complex or simply ignored the issue. Over the past ten years, AES committees have worked on the development of PA-422 and its successor, AES-24. The result is a sophisticated control protocol that has been implemented in a number of successful products, nearly. Unfortunately, while each of these implementations incorporates much of the basic requirements of AES-24, they are not compatible with each other.

We often create networks (by definition, anyway) of audio equipment but still lack a widely supported control protocol to link them together. There are a number of protocols that are supported by more than one equipment manufacturer, the most well known is Peak Audio's Cobranet. However, you won't find very many power amplifiers with Cobranet RJ45 jacks on the rear panel. Someday soon, just not yet.

Even if the equipment did share the same networking protocol, you will be running a number of applications to control each component. Unless you want to write your own application in MS Visual Basic. However, if you don't want to be in the code-writing business (other industries pay better for this) then you have to switch between the mixing/matrices control application, signal processing control application, and the power amplifier control application. If you are lucky, these might share a single computer, but will it have enough communication ports? I wouldn't think of showing up on-site to set up a sound reinforcement system without a laptop computer, but what is the most common connection for controlling the signal processing gear? An RS-232 serial port connection made sequentially to each type of device. We were further ahead with PA-422.

Sound systems now routinely include lots of parametric equalization, signal delays, brick-wall protection limiters and other sophisticated signal processing. All of this is contained in a few small boxes of DSP with control and monitoring ports for connecting a computer. If you want to integrate the measurement of the system with the processing control, it is likely you will step even farther back in time, to MIDI. A control protocol developed nearly two decades ago.

Our most universally accepted control standard is still the dry-contact closure (GPI for those that like everything reduced to three letters) that has been with us longer than anyone can remember. It shows up on many signal processors and power amplifiers that offer remote control. It's digital (at least binary), but it has a distinctly retro quality that defies direct connection to Ethernet. You won't find a GPI connector on your laptop, either.

We need a common network protocol to address our sound system components even more than we did ten years ago. Let's hope that the groundwork that has been done by the AES standards committees and a few visionary manufacturers will lead eventually lead to a universal method that is widely adopted.

While we have successfully reached the end of a fertile decade in sound reinforcement system development, many of the fruits of seeds sown in the '90s won't ripen for a few more years. We may leave the 20th Century dressed in digital clothing but we are still walking in analogue shoes.

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

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