THE NEXO TD CONTROLLERS

A number of our clients have asked us questions about the Nexo loudspeaker controllers.

They generally ask the same ones ;
• What do they do?
• How do they work?
• What makes them different to other
• "loudspeaker controllers"?

With loudspeakers getting smaller and smaller and amplifiers getting larger and larger what chance do the poor old loudspeakers stand of being protected from all this new available power? The quest marches on for the "ultimate" loudspeaker system that is about the size of a packet of fags and "blows the doors out" when you turn it up. Whilst it’s true that speaker boxes are diminishing in size, the need to protect the (sometimes tiny) drivers is ever more apparent. Enter the Loudspeaker Controller.

The idea is not new. Companies were developing the idea back in the early eighties after some bright spark realised that if a controller knew about the behaviour of the speakers attached to it, then it could make decisions about whether or not to turn the system up or down to compensate for the excessive overdrive. Most early controllers merely acted as system limiters with circuits to prevent amplifier clipping and overall level control which kicked in if the output of the system was exceeded.

However, these type of controllers were little better than a standard compressor/limiter. True, whilst they were connected to the amplifier outputs to "sense" the signal arriving at the cabinets they performed more accurately than a "standard" compressor limiter, but performance was often very audible and the systems sounded none too good.

The latest generation of controllers such as the Nexo PS10 / PS15 / Alpha series (and the new Digital NX241) include many more functions than the rival manufacturers’ early designs thus enabling far more precise system control.

Each controller contains a precise "map" of its respective loudspeaker cabinet. This "map" contains all the known characteristics of the behaviour of the loudspeaker and cabinet configuration. This is achieved through extensive and exhaustive testing and computer simulated modelling by the R+D engineers at Nexo in Paris.

Signal is passed from the source (the sound desk) and carefully shaped in the controller to match the desired sound characteristics of the box. Shaping (EQ) is done only where absolutely necessary and, most important, phase errors brought about by the shaping process are corrected.

The correctly shaped, phase corrected signals are then fed to the amplifier inputs as normal.

As with most controllers, sense lines are brought back from the amplifier output terminals so that the controller knows exactly what signal the speaker is being driven with. Based on this signal, the controller can then use it to make decisions about its outgoing signal. If the sense signal falls within the limits of the internal "map" then no action is taken and the signal passes straight through but if an excessive power condition is present anywhere in the band that could potentially be damaging to the loudspeakers then the controller acts.

The key words here are "anywhere in the band". These controllers do not simply apply an overall "limit" to the outgoing signal, they are able to select the areas in the frequency band that fall outside the limits of the "map" and deal with them accordingly without damaging the overall sound and level of the system.
Selective voltage controlled equalisers (think of them as sliding filters) are able to deal with just the problem frequencies, only acting when necessary so that audible correction is minimised.
Dynamic control dramatically reduces the perceived effect of the limiting thus ensuring audible "pumping" is minimised. Voice coil temperature is constantly monitored and controlled as necessary as is the drivers’ displacement (excursion) limits.

The result is a well controlled smooth sounding system that benefits from increased reliability, better overall sound and a high power-to weight ratio.

Important:
Currently, there are NO general purpose processors (loudspeaker or otherwise) on the market that can successfully emulate what the Nexo controllers do. Whilst other units may indeed have the processor power, they do not have the important algorithms present to make the system sound and operate as intended.

The latest in the Nexo generation of processors is the new, digital NX241. If you are a hire company and have the need to use your cabinets for lots of different applications the NX241 is a useful tool.

The NX241 now has available program setups to cater for all of the current range of Nexo products, including the all new revolutionary GEO series.
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