Understanding radio mics
Sun, 15 June 2008, 09:28 pmDavid Ashton13 posts in thread
Understanding radio mics
Sun, 15 June 2008, 09:28 pmAs this is the tech talk column I thought it may be a good idea to cover some of the common problem areas and start with this common problem.
Now you will see mics with 16, 32, 300, 700 or 1440 channels, this does not mean that you can use anything like that number of mics together.
Radio transmitters are like musical instruments [in that they produce harmonics which are multiples of the base frequency], and these harmonics interact with each other to restrict the number of usable channels.
As an example, the Redback 16 channel mics have 6 channels which can work together, the main mics I hire are the 700 channel series but only 16-17 channels will work together.To get more channels I am now getting in the Sennheiser 1440 channel units and while they are coy about exactly how many channels I will get, it should be 24+.
Now other areas to consider are interference from other radio sources like in ear monitors, which tend to use the same bands and radio talkback systems which I am now also importing as prices are lowering.
If you are using half a dozen radio mics there is not likely to be a problem but once you start adding talkback and in ear monitors you will need some specialized assistance.
And as I said in an earlier piece, the radio part is only the beginning, the complexity of multi mic mixing a live show added to the potential harmonic interference means that rehearsing with the full system is crucial and failure to do this and find potential problems can lead to disaster.
In short, radio mics are not a panacea so please bear this in mind.
understanding radio mics
Mon, 16 June 2008, 06:52 pmIt's good to see some feedback, I originally tried to keep things simple to explain the problems to the non technical fraternity, however I would like to address a couple of points raised.There are 3 styles of mics generally used, the tie clip type is pretty useless as it will pick up clothes noises, the headset type of mic is fine for rock'n'roll situations where it does matter about the look but by far the most useful are the "bud" mics, taped to the face below the ear, there is no clothes rustle and the mic picks up the resonances of the voice and sounds more natural, this is why it is universally used in opera and musical reinforcement, placing the mic too close to the mouth will give a "breathy" sound and will overdrive the mic causing distortion.
The interference from other sources is an ongoing problem and was the main reason for me buying mics with more available channels.
Once again I would like to encourage other techs to use this forum to bring forward aspects of the tech side of the business so that actors and directors can get the most out of their sound, lighting, scenery and props.