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VMB Debuts Digital Controller With Air Absorption Compensation
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Version 3 of the VMB ARKEOPS digital controller provides air absorption compensation.

The attenuation effects of air are well known. At 15 000Hz, for instance, 12 dB of loss can be observed at 30 metres (100 feet) with 30% relative humidity.

This makes an otherwise flat frequency response at close range totally dull when the audience is located at a distance. The problem gets worse as humidity decreases and to a less extent when it gets colder.

Air attenuation is currently compensated mostly just “by ear”. This is, however, a very complex task to accomplish with any precision.

In addition, humidity as well as temperature can often change significantly over time, which means that a system that was tuned when the rig was set-up may not be valid for show time or as the show progresses.

With version 3 of VMB’s ARKEOPS controllers, users may specify, for each of the outputs, a distance for which a frequency response correction is applied, based on a given relative humidity and temperature.

“To our knowledge, ARKEOPS are the first universal multi-way loudspeaker management controllers provide high frequency response compensation for air losses”, notes Javier Matalí , VMB’s Director of Marketing.

“There is an impressive improvement in sound quality for common distances such as 20 or 30 metres (65 or 100 feet). Other than bringing linearity back to the system, adapting it to changing atmospheric conditions is as easy as editing the temperature and humidity parameters on the controller. “

With a weather station on top of the mixer, users from dessert Las Vegas to humid Singapore will wonder how they could manage without air absorption compensation for so long”.

The ARKEOPS series of loudspeaker management controllers is comprised of four 1U high models, differing only on their number of inputs and outputs. ARK-24 and ARK-26 feature two inputs as well as four and six outputs, respectively. ARK-44 and ARK-48, with four audio inputs, provide four and eight outputs, respectively.

According to the company, ARKEOPS controllers are designed as true “Swiss army knives” for processing sound systems in fixed or mobile applications, both in terms of the amount as well as the diversity of processing and functionalities available.

Model ARK-48, for instance, boasts a total of 252 second order filters. On top of the standard EQ types you’d expect to find on the equalization section, you’ll see resonant low-pass, notch and resonant shelving, as well as two types of all-pass filters for phase adjustment.

Raúl Jordán, DSP engineer for VMB, states “You never know what you’ll come across. That’s why we try to offer all sorts of tools that may be useful at some point. A notch filter may come in handy to fight feedback or pinpoint a source of hum. And all-pass filters let you combine two different boxes together coherently if you have to.”

Crossover filters include Bessel, L-R and Butterworth, with slopes from 6 dB to 48 dB/octave, adjustable in 6 dB steps, providing flexibility. A 6 dB/octave slope, for instance, corresponding to a first order filter, allows for frequency shading.

Inputs may use up to 29 filters, parametric or graphic. Outputs provide 9 parametric equalizers.

Given that a loudspeaker component may be damaged by thermal damage (due to excessive average power) as well as over-excursion (peak power), ARKEOPS utilize both a peak limiter as well as an RMS compressor/limiter.

Both are fully adjustable. Attack and release times may be specified in dB/s, or an automatic mode can be made use of that chooses optimum parameters based on psychoacoustic research for minimum audibility.

Dynamics processing includes a noise gate on every output; while noise is not an issue on the average rock ‘n’ roll gig, there are low ambient noise applications where it can be a valuable feature.

Five levels of security are used. A user may only be authorized for muting outputs, whereas other users maybe allowed loading of presets as well. Settings may also be blocked so that, say, a band engineer could only be granted access to input EQ.

Other features include polarity and delay on ins and outs, routing of any input to any output and a signal generator with sine and noise (pink or white).

The USB port simplifies updating firmware as well as editing and monitoring. The latter includes limiter compression on top of input and output levels meters.

When a number of units need to be controlled, an Ethernet network may be deployed using the integrated roadworthy EtherCon connector.

Another unique ARKEOPS features is the ability to import amplitude and phase response curves for each of the bands from a number of analyzers.

The overall effect of the processing on the frequency response curve can be examined without the need for further acoustical measurements.

Other features:
- Plug-and-play USB connection; no drivers needed
- Low latency (0.5 ms analogue in to analogue out)
- 24-bit / 192 kHz converters. Best converters available and careful electronic design achieves a dynamic range of 120 dB
- Instant A/B comparison. Seamless audio editing, even with delays

The new ARKEOPS are shipping now. Firmware update is free for existing users.

For more information:

VMB Website



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