Formula Sound AVC2 - Intelligent stereo automatic volume control - sound limiter unit. Provides system protection without reducing dynamic range (Includes rear panel security cover).

AVC2 - Automatic Volume Control The Sentry, AT1 and the AVC2 are purely sound control products but they are used in different applications. The AVC2 fulfills the need to control fixed or installed sound systems as opposed to temporary or mobile systems. The reasons for installing this equipment would be to address:-

• Health and Safety issues in colleges or training environments, or in professional working environments, e.g. in recording or broadcast studios to control the monitoring system. (We have supplied units to several radio stations for this application.)
• Noise pollution situations, e.g. entertainment venues which are located near residential property. This is by far the largest use of this product. The problem with sound systems is not the equipment, but the operators. We cannot take away the knobs and controls which they need to do their job. What we can do is control the maximum level at which the system will play irrespective of what they do. The AVC2 is an Automatic Volume Control unit and as the name suggests behaves just like someone leaning over the operator's shoulder and turning the volume down each time he tries to turn it up above what is allowed.

The more the operator tries to increase the volume the more the AVC2 will decrease it, so the system will barely change in perceived volume level. Eventually the operator will run out of controls to turn up. If the AVC2 is driven to maximum the output level will be reduced by more than the increase in input level. The system will probably now sound distorted and generally not very nice but the volume will be at a lower than normal level. Turning down the volume will allow the system to return back to normal operating level. (Maturity, we are told, is knowing that you can turn a volume control down as well as up)

It should be noted that this unit is not a compressor and will not significantly change the dynamic range of the music. This is because it is fairly slow in its action and therefore has a response time of a few seconds depending on musical content. There are no user controls on the AVC2 to be tampered with, only a bar graph meter showing how much control the AVC2 is exercising.

The AVC2 works by controlling the signal level before it gets to the loudspeakers. As this signal level is directly proportional to the noise the loudspeakers produce we do not need a measuring microphone for the system to work.

This explains the AVC2 in basic simple terms. More detailed technical information is available in the brochure. Although the AVC2 will control any sound system and do so in a way that won't embarrass or upset anyone it can only perform satisfactorily if it is installed and calibrated correctly in the venue. It is not practical to use the AVC2 in a mobile situation or where visiting artistes, bands, DJs, etc. bring their own equipment. The reasons are many, such as the problems of interfacing this equipment to visiting sound systems in the time available before a performance; where to connect it; having the correct connectors available; having the time to calibrate the equipment in the venue; having technical staff available to do the work.

So how to control mobile sound systems? The common factor to all sound systems is the mains power supply, therefore if the power is controlled the system can be controlled. Technically this is like taking a sledge hammer to crack a walnut but it is simple and effective, and as long as a few basic facts are recognised and understood a very workable system can be provided. This is not a new concept. There have been systems around for years, which work on this principle, but some of them had inherent problems.

Some problems with existing equipment:-

• The use of a conventional measuring microphone that can be easily tampered with and its response modified.
• No indication of actual sound level - only an indication of when the sound level is too loud, which is usually too late because the power is already off.
• Only one mains socket controlled. Artistes simply connect to other sockets.
• Some units use the 'A' weighting scale for measurements. 'A' weighting is not suitable for measuring entertainment noise. (For more information see FAQ section on weighting). • Mains power switched back on with no warning. This can damage audio equipment and the owners of this equipment may have grounds for compensation.