A common misconception is that these are newly available devices when they have been used for over 40 years. However, it is only in recent times that size and battery capability have improved to the level where they may be easily concealed. Apart from expense, the main problem with radio microphones is the limited number of channels that are available and the lack of quality and reliability. In every case a conventional cabled microphone will work better. The differences on a good day will be small, but signal-to-noise ratio and frequency response will always be poorer. With good systems these differences can be usually be overlooked due to the advantage of complete freedom to travel anywhere on stage. The facts of life concerning radio microphones are these; Radio microphones will suffer from hisses, clicks and odd noises Batteries will fail at crucial Microphones will fall off during vital moments Cast will turn them off - and forget to turn them back on Mike sharing will not work reliably The audience will hear something they shouldn't Most of these problems can be reduced, but probably not solved. Here are some possible solutions. The signal path between the transmitter and the receiving aerial should be as short and uncluttered as possible. This includes other members of the cast. Radio wave do not travel easily through large sweaty bodies and certainly not through metal costumes (think Tin-man in panto or suits of armour). If the transmitter pack has a 'dangly' 1/4 wave aerial it must hang free, not be 'scrunched' up to keep it out of the way. Make certain the microphone is attached to something that doesn't make a noise. The whale bone stringers in a soprano's corset make the most amazing sounds! Check that the microphone cannot be covered by any material that will rub or crackle. Batteries - use well known and trusted brands. Mistrust any information that states "Battery life in excess of 10 hours". A brand new alkaline battery is safe for a couple of shows maximum. You might squeeze the third one in but on the other hand it might fail mid finale. My own preference is for Duracell, but do watch out as they are also slightly larger which could cause problems with some makes of equipment. NEVER use re-chargeable batteries. Ni-cad have a discharge pattern which prevents the user from accurately assessing how much power is dead. Most transmitter packs have a red indicator which goes out with an hour or so left in the battery. With Ni-cad's this light may only go out for 30-40 seconds before the battery goes completely flat. If the cast are clipping the microphones on make certain they know how to fit them reliably (and in the same place each night). Some brands of clip are very difficult or fiddly to fit and the microphone can fall off during the performance. Mike pack swaps are the frequent cause of most mistakes, as the artiste often relies on others to fix the clip in position. The cast must trust the sound op to switch the microphones on and off. Mistakes will be made from time to time, but that is the sound ops job, not the artiste. Very often the sound op will test with the PFL that the mike is working. The short 'dip' into the channel enables a check to be made that the mike is on, there are no crackles and most importantly, that the artiste is where they should be. Imagine opening the mike for a line of off-stage dialogue when they are still in the dressing room or worse. With advance warning the sound op can warn the DSM that "Fred is not where he should be, in fact I think he is in Johns dressing room" or similar. Sound ops develop thick skins as part of their profession and get quite used to hearing things about themselves that are not flattering. Mike swaps will go wrong if they can! Meticulously planned mike swap list fall apart if just one swap is late. Never allow anyone to change the system to 'sort it out'. Invariably this just creates another problem later which may be worse - plus it messes up the desk labelling and EQ settings. If the mike is not available when required then the artiste must go on without it and cope. The sound op will 'kill' the mike as soon as the artiste makes their exit, in the same way that they made it 'live' before the entrance. It is crucial that the artiste realises that they may be waiting in the wings with a live mike and they must not talk to anyone just before or after. If this does cause problems where the actor may have to speak in the wings then the action of making the mike live and killing it afterwards may be controlled through the DSM for safety. Cues on the lines of "Lose the mike............ Mike gone" should work. Sound ops must also develop the knack of not hearing or seeing anything. This is quite easy to master after a while and you can just disappear into the background. People new to the department often get embarrassed at the mike fitting stage, but if this is handled professionally then it should not be awkward to either party. Hiding the pack itself is not too difficult as long as there are few swaps taking place. The best place may not be the most easy place to get to (another reason not to let the cast turn them on and off). Men's costumes tend to have more natural places to conceal transmitter packs. Both trousers and jackets frequently have pockets. Make certain that the cast will not remove parts of clothing to which equipment has been fixed. Packs may be slid into thin cotton bags and tied around the waist. Depending on the cut of the clothes the position can be altered. Side works well if there is enough space and does allow sitting down. If no sitting down will occur then a more comfortable position is down the front of the trousers in a pouch. Ladies costumes due tend to be more problematic due to their design, which rarely has pockets or concealable spaces. Even in tightly fitting costumes there may be suitable space available although the shape of the actress does play a large part. A good location is the small of the back. The pack can be located in a pouch or if one is not available then normal stage tights make a good alternative 'home'. These tend to fit higher into the waist and are usually more strong and elastic than standard types. If the pack has interchangeable aerials then better results may often be achieved with a 1/4 wire type dangling down into the skirt. Rotating the pack upside down also allows the wire to exit via the mesh gaps in fish-net style tights. Travelling up to the waist band and then down again reduces the efficiency of the aerial, with a corresponding reduction in performance. The small helical whip style aerials used for VHF systems and the stiff 1/4 waves used for UHF often get hard pressed to the body by the clothing and this reduces efficiency again. This is made particularly worse by those artistes both male and female who become 'clammy' and sweat a lot while on stage. The salt content is also conductive and tends to reduce the output even more. Sometimes a small amount of tissue or even kitchen roll can reduce the effect to manageable proportions. Although I have never had to use the technique myself, some sound ops promote enveloping the whole pack and aerial system in a condom, which does seem to help, although complicates battery changing. Where the small of the back location is not feasible for either costume or visibility reasons then it may be possible to hide the pack under the cleavage. Many costumes are loose fitting at the front and the space can easily hide most packs. The pack can often be hung from loops dropped from the arm holes or attached to the wire of the bra if fitted. If the bra is underwired be aware that the aerial system needs to be kept as far from it as possible to prevent any electrical coupling. Some styles of female costume by nature have very few places packs can be concealed. As an example consider the 'Miss Saigon' oriental style dress. The style prevents most usual positions being considered and there are only two real places possible. If the actress has very slim legs then the pack can be secured with tape to the inner thigh. Although slightly uncomfortable, this is a fairly secure location and should not come loose. If this location is not suitable due to build, then the only real practical alternative is to conceal the pack in a hair piece or small scarf style addition to a hair dressing. This method is the preferred arrangement in Miss Saigon, but does require the service of a hairdresser and sound op during the make-up session. It is obviously no use if the pack is to be shared. The inner thigh position can be recovered for a swap quite quickly, but takes a little longer to rig successfully.
The crucial step to take is that no matter where the pack is sited, the microphone itself is placed as close to the mouth as possible. In virtually all cases the microphones used are OMNI-DIRECTIONAL. They pick up sound equally well all round. As we have seen earlier feedback is still a majorproblem and giving the cast freedom to go anywhere on stage will make it worse. Having the mike as close as possible maximises the volume available before feedback, before any equalisation. Apart from the conventional clip-on mounting, where no swaps are involved the best place by far for mike placement is either on the hairline centrally at the front or side mounted on the temple. In both cases the mike tip can be secured with spirit gum and then the cable dressed into the hair for the first position or taped to the above ear region for the second. Make-up can disguise the installation quite successfully. Mounting the microphone in this way does interfere with the frequency response so some EQ is nearly always required to give good tonal balance. Most clip on microphones were designed for chest mounting (LAVALIERE - originally on a lanyard around the neck) and the extra resonance achieved from the chest cavity was allowed for in the design stage. Even if mike swaps are required it may be possible to just swap the packs and have separate mikes for each cast member which makes the dressing simpler. Do be aware that direct mounting of microphones on the cast will lead to more microphone failures. Microphones 'sweat out' and their sound becomes dull with repeated exposure. Makeup, hairspray and other unwanted material also finds its way into the mike. One manufacturer is currently promoting washable microphones, while another is rapidly building a reputation for building 'bomb-proof' types that even survive immersion in salt water! The most widely known microphone used is the Sennheiser MKE-2 type which is available in both black and pink versions and has a very tough cable. A version is also available (the Red Spot type) which has reduced sensitivity for occasions where sound pressure levels will be high.
Most of the material written around the studio use of microphones holds good for performance, with only a couple of extra details required. Stage use will wreck expensive condenser microphones, and their subtle differences in overall sound quality may well be discounted in favour of reliability and lifespan. The power supply required by many condenser microphones may also not be available from every mixing desk. It is often also required to amplify the sound of the actor on stage. This is probably one of the most common tasks required and is usually one of the most difficult to accomplish. The enemy is normally feedback. Any microphone can be pointed at the stage, amplified and sent to the audience. Once the feedback point has been reached, and any equalisation completed then that is that! Any more volume and the system becomes unstable. Increasing the number of microphones only helps slightly. It tends to fill in some of the more distant pockets, but the overall volume level still fails to come up. Hanging microphones frequently fails to perform well as we need to be able to control their directional response. Cardioid microphones hanging present their least sensitive side to the stage roof, where feedback is not likely anyway, while presenting one of their most receptive areas to the already sound filled auditorium. Cardioids on the stage edge pointing upstage present their 'deaf' side to the audience which does help. Specialist microphones are available which use special techniques to produce a directional pattern that is long and thin. These RIFLE microphones can help a little to enable what is being said upstage to be heard, but suffer the disadvantage that they do need to be pointed more accurately. An alternative to the rifle (or shotgun) microphone is the so called Pressure Zone Microphone (PZM) or boundary effect microphone. These types sit on the stage floor and have a broadly hemispherical pick up pattern. Experience shows that in some venues they do produce more even sound coverage than rifle types, but are limited in volume by the pick-up from the auditorium.