Optimod
Optimod is the brand name of sound processors and digital signal processors from the US company Orban from Tempe (Arizona) .
The term is also used as a generic name for sound processors for the broadcasting sector (similar, for example, to the speed of handkerchiefs). Optimods usually contain at least one adjustable compressor , equalizer , enhancer , AGC ( Automatic Gain Control ) and a multiband limiter . The Optimod can significantly change the sound dynamics of a piece of music: Quiet passages become louder and vice versa.
Areas of application
An Optimod is not just a sound processor, in newer models it also has a so-called multiplex limiter, which limits the multiplex power (the FM broadcast signal) to an adjustable value. This is important because international agreements provide for a peak deviation of the modulated signal of 75 kHz . Thus, the modulated frequency may be raised or lowered by a maximum of 75 kHz. In addition, the MPX power is limited to −0.1 dBr (loudness limit). The responsible Federal Network Agency monitors compliance with the technical guidelines on a random basis and can also impose fines on the broadcasting network operator if the values are not adhered to (who will usually pass this on to the program provider who has delivered a non-standard signal).
This is part of the reason radio stations use an Optimod. In order to achieve a higher volume at least subjectively, the audio signal is compressed. The difference is particularly noticeable near the border. In some of Germany's neighboring countries, compliance with the guidelines (which apply everywhere) is obviously not monitored too strictly, so that overruns are sometimes the order of the day.
In addition, an Optimod often corrects minor level errors in the studio, which can occur especially in self-propelled mode, through the upstream automatic level control .
Television broadcasters also use broadcast compressors like the Optimod.
disadvantage
Sound compressors often impair the listening experience with "more demanding" music that has a high dynamic range (ie requires more bandwidth), e.g. B. orchestral or vocal music. The music usually sounds slightly distorted in these cases. The use of compressors in satellite transmission is particularly noticeable , as many radio stations simply send the signal processed for the VHF route with an Optimod unchanged to the satellite.
The use of the signal after the complete Optimod processing as headphones - Monitor signal for the radio host or Spokesman is now often no longer possible, since the newer device versions (about Orban FM 8500 ) digital work and the required computing time a slight signal delay have. This “latency” is usually between 11 and 70 milliseconds, depending on the intensity of the sound processing, and is therefore extremely irritating and unintentionally influences the speed of speech. Some broadcasters make do with tapping the signal in an intermediate processing stage, which has a lower delay, but cannot convey the exact sound impression of the entire processing. Orban offers headphone monitor audio outputs with a constant latency of only around 2 milliseconds for its new models ; regardless of the overall delay of the system. In addition, some devices have an ultra-low-latency structure in which the latency of the entire sound processing is an unproblematic 3 milliseconds. According to Orban, this happens at the expense of the loudness impression of the transmitted signal.