The Evolution of Audio Monitoring

LOS ANGELES—Decades ago, the method most commonly used to check audio at various stages in the transmission chain was to route the signal to an amplifier and a small, poor quality speaker propped up on top of the rack. These days, loudspeakers are often built into rack-mounting monitoring and measurement products, and the audio quality is light years ahead of that decades-old method.

The idea to integrate speakers into a rack-mount monitor reportedly first occurred to Wohler. "There's no doubt that we invented that, 23 years ago," said Jeff McNall, product line manager for Wohler's audio and video products.

Wohler's broad range of audio monitoring products variously includes two full-range speakers, two speakers with a shared subwoofer, or two speakers plus two subwoofers. However many speakers are included, the product design must take into account a number of issues to ensure quality audio, noted McNall.

First and foremost, of course: "We make sure we have the best speakers we can in there. We look at how they're mounted, so they don't rattle in the unit. And you want to look at shielding, although it's less of an issue because you don't see CRTs like you used to."


According to Martin Dyster, audio business development manager for U.K.-based TSL, the company has benefited from expert design assistance with some of its products. "They have been designed in cooperation with a company that we just acquired, Celtic Audio, and John Watkinson, one of the founders. John was instrumental in designing some of the enclosures, particularly on the AMU1-CHD+, the PAM1 and the PAM2 range, and the AMU1-3G," he reported.

Despite the effort, commented Dyster, "It's interesting to note that our push towards getting audio quality into small enclosures is not always appreciated. Acoustic quality is not something that is particularly important to some customers. Sometimes they just need to know that audio is present. You're not supposed to use [these products] for mixing program."

That said, "We do strive, particularly in the mid- to high-end product range, towards as high a quality as we can possibly get given the restraints of the enclosure," he added. And although these products are often little more than confidence monitors, "Some of our monitoring units end up in post production, where they're the only means of monitoring."

And some clients do need mix capabilities. TSL's brand new AVM-T-MIX, reportedly the world's first rackmounting touch screen-controlled audio mixer/monitor, incorporates a 4-way speaker system plus mixing functionality.

Wohler AMP2-16V
"The launch is being supported by a very large order from the BBC for their Manchester studios," Dyster revealed. "The fact that it has speakers onboard has been a considerable positive for the customer as they've dispensed with external speakers in many applications."


Harris Videotek's offerings, while not as extensive as some manufacturers, have also been designed to overcome some of the challenges of a typical application. That can include noisy environments such as master control, transmission and machine rooms, as well as remote vehicles and flypacks.

"We did spend a good deal of effort making sure we had enough output," said Paul Keller, Harris Videotek test and measurement products manager. "The low end is a problem because it's a limited size enclosure, so being able to listen for hum was something we worked at."

Harris offers a unit with built-in full range speakers, the CVM-306 multiformat signal analyzer, as well as an audio panel that combines with a measurement device. "The APM-215 audio-only panel has a subwoofer," offered Harris Videotek product manager Jeff Witman. "One ribbon cable will tie that to the output of a TVM or VTM or CMM-LA loudness analyzer, and let you select from the eight audio channels to monitor any particular pair."

Harris CVM-306 Harris also produces the VMM-4SNY, a video measurement module for certain Sony monitor models. When fitted into the monitor's option slot it provides all the functionality of the CMM analyzer, routing the audio internally to the Sony's built-in speakers, if it has them.

Linear Acoustic, well known for its monitoring and processing products, offers two units with built-in speakers, its LAMBDA and LAMBDA II audio and metadata monitoring solutions. Those products feature a premium, acoustically tuned speaker system with digital crossovers and bi-amplification. Conveniently, a delay of up to three frames may be applied to synchronize the audio to external video monitors.

LAMBDA's speakers output a full-time 2-channel LtRt or LoRo downmix. In its 16-channel mode, all applied audio channels may be reproduced individually or as a 5.1 downmix.


TSL's mid- to high-end products are designed for multichannel environments, and as such typically include downmixing to the two speaker channels. "An ability to do a downmix, whether it's derived from Dolby metadata or from algorithms, is important," said Dyster.

On the new AVM-T-MIX, Dyster continued, "You can define channels as being 5.1, LCR, dual stereo, or multiple mono, derived from SDI, analog or AES. You can downmix and mix them together."

Wohler's flagship model, the AMP2-16V, allows any number and variety of audio sources to be monitored, according to McNall. For example, he said, "You could see the incoming feed on SDI 1, AES, and a set-top box. I could look at all of them at the same time. That makes the box kind of unique. Sky, in the UK, has 100 AMP2-16Vs and it has become the house machine for Starz Encore."

Not every customer needs every flavor of Dolby codec, continued McNall, leading Wohler to introduce an option at this year's NAB Show for a simple Dolby Digital card. "Some people never need E, so why pay a premium? With just Dolby D, they have AC-3 and can see dialnorm and everything. That's a unique positioning for us."

McNall can personally attest to the high quality of the audio in Wohler's monitoring products, as he related: "We had a party at NAB in a small suite and I brought along a couple of our units and my mp3 player—and it was fine!"

Steve Harvey began writing for Pro Sound News and Surround Professional in 2000 and is currently senior content producer for Mix and a contributor to TV Tech. He has worked in the pro audio industry—as a touring musician, in live production, installed sound, and equipment sales and marketing—since November 1980.