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Designing an Audio Monitoring System

VAN NUYS, Calif.
With no two broadcast facilities or groups sharing identical operating philosophies, rackmount multichannel audio-monitoring panel designs run the gamut from the most basic analog-only units to highly sophisticated digital systems with metering and multiple video screens to handle all requirements.

And nowadays, the design of audio-monitoring panel systems is very much driven by the configuration of the gear elsewhere in the system.

"The networks are now distributing their material in Dolby E, so having Dolby decoding is getting to be more and more important," said Paul Keller, Test and Measurement product manager at Harris' Broadcast Communications Division.

As a result, many monitoring units handle a minimum of eight input channels—perhaps a 5.1 Dolby Digital stream, and maybe the Lt Rt downmix.

But Keller says that clients are demanding more 12 inputs.

Marshall's AR-DM2 monitor "They really want 16, which is what you can do with embedded audio with digital video," he said. "And with dual link and 3 gig you can do 32 inputs; soon enough they'll be asking for that." According to Keller, of the three units in the Harris Videotek APM range, the APM 210 is designed to also work in conjunction with other test and measurement devices.

"It connects to other equipment, for audio only, the ASM 100; for video, any of the TVM and VTM series of test instruments; and depends on that to do the de-embedding or the D-to-A conversion," he said.

For convenience, eight audio channels are introduced via a ribbon connector from those other units, with an additional pair available on XLR or RCA connectors, he said.

Wohler is among those manufacturers offering I/O modularity, which allows users to specify a system with a combination of analog, digital, Dolby or SDI connectivity to suit their plant infrastructure.

Kim Templeman-Holmes, Wohler's vice president Sales and Marketing, summed up the principal requests from his clients succinctly.

"Everybody wants to go 3G, they want data monitoring, and they want far more for less money."

He observed that 16 channels is fast becoming a minimum requirement, especially for satellite operations carrying multiple Dolby-encoded programs.

Wohler's AMP2-16MSDI "In the U.S. and Europe, people are looking to monitor multiple sources and they want to see the metadata," he said.

As it becomes more commonplace, 3G will add even more inputs to be monitored into a Wohler unit such as the AMP2-16, which includes metering and OLED displays:

"You could fit five 3G cards, which would give you five times 16 inputs, although you could only display 16 at once," said Templeman-Holmes.

Marshall Electronics, which principally manufactures video products, also offers some modularity.

According to Mark Fisher, Marshall's product marketing manager, the company's AR-DM series of digital audio monitors may be specified with the type of I/O required by the customer. He noted that the company's analog-only AR-AM series provides an alternative, entry-level solution. All AR-DM units accommodate 16 inputs.

"We offer a variety of different modules, including the Dolby Digital decoder module," said Fisher. "If the user doesn't want or need that, obviously they don't have to pay that extra expense. It makes it very cost effective and also future proof, so that the installer or integrator can mix and match their input modules."

Ward-Beck's managing director, Eugene Johnson, observed with the advent of embedded audio it's critical that there be a convenient way to monitor it. However, some analog is still likely to be found in most plants alongside digital streams.

The Videotek-ASM-100 from Harris "One of the things that we find more and more important is that we need a demuxer in most of these monitors," said Johnson. "But you still have to be able to handle analog. People like NEP, in the mobile world, really appreciate the fact that we not only take in the HD-SDI signal, but we can also take an analog signal."

He observed that in doing out-of-house production, there are always unknowns that have to be addressed and mobile production companies have to be ready for anything.

"When these guys show up to a venue they never know what they are going to be fed," he said. "It's critical to have something that can take analog, embedded audio, and digital audio. So much of TV production is being done in the mobile world these days that you really need to have a broad signal-handling capability in your monitoring product. There's so much legacy gear out there."

While some monitors such as the Ward-Beck AMS4, AMS8 and AMS16 were designed to be the Swiss Army knives of audio monitors, Johnson observed that such flexibility should not come with added complexity on the user's part.

"It has to be as flexible as it possibly can be, but you have to guard against making it so flexible that it's inoperable," he said. "You don't want operators to have to sit there and go through layers and layers before they get to the layer they want."

However, with DSP at the core of the company's AMS line, creating a user-friendly environment doesn't really create a large challenge.

"It's easy for us to take the features that a particular group or operator wants and bring them to the forefront," Johnson said. "The others can be buried in the back, so it's not something that can trip them up."

Looking forward, it will be only a matter of time before customers begin to expect 3G capability in audio monitoring products. "That's really come on strong in the last six months of so," said Templeman-Holmes. "All of a sudden, even though stations don't have the infrastructure to support 3G, they are now demanding it."

Harris's Keller concurred.

"Several of the major networks are working on master control rebuilds and they're making them all 3 gig-ready," he said. "[But] all the interest so far in 3 gig has been from manufacturers who are developing equipment and [from] people buying routers and distribution equipment that is capable of 3 gig, to make sure that they are getting what they paid for and to be able to test it."

He added that currently there wasn't much in the way of 3 Gbps source material.

"Sony is supposed to release a board for the SRW tape machine and for their switcher this summer; that will be the start of it," he said. "The HDCAM SRWs are the format that the networks all use for their primetime programming."