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.
When using wireless mics in
Mon, 16 June 2008, 08:31 amWhen using wireless mics in an amateur background, it is important to get the actors to rehearse with them for a lot of reasons:
There may be local sources of interference that only pop up at irregular intervals so if you can use them on the same nights you will be performing on, there is less chance of getting caught out by interference during performances.
If using large numbers of wireless mics, your crew needs to work out a discipline of testing each wireless mic with each performer and instructing them not to turn the beltpack off once tested to avaoid an actor going on stage with their mic turned off.
Two actors wearing wireless mics can have proximity cancellation occurr, where the sound from an actor is picked up by their mic and a little time later is picked up by the other mic. These two different signals can cancel out in the mixer, so the director needs to be aware when this occurs and reblocks or gets the actor to change the side of their face that their wireless mic is on, or gets the sound tech to take one mic out of the mix for that moment.
You need to set up a discipline of recharging you beltpack batteries or budget for battery replacement so actors always have fresh batteries for every performance.
Try to get unobtrusive, flesh coloured mics and practice with them so they are an integral part of the actors costume and makeup.
Wireless mics are great for actors who have colds or in large halls as it saves their voices for long seasons, however make sure they don't rely on the mic as a wireless mic cannot work well with actors whispering due the to signal to noise (hiss) limitations of the system.
The person mixing a show with radio mics needs to have a script marked with who is using what mic when, so the mic is only added to the mix when required. This gives the actors confidence to leave their mics on at all times.
When using large numbers of wireless mics, you need a tech backstage to check mics before and during a show and ideally have a spare set to swap out any faulty ones as wireless mics can be succeptable to sweat interfering with the mic capsule.
And so the list goes on.