Microphones for Event Crew

01How a mic works

A microphone turns air movement into a tiny electrical signal. Two designs do almost all the work at events: dynamic and condenser. They behave differently, they need different care, and picking the wrong one is how a good job sounds bad.

Dynamic or condenser: which one?

Phantom power (+48 V)

Phantom power is 48 volts sent down the same XLR cable that carries the audio. It sits on pins 2 and 3 against pin 1, so the audio is not affected. Condenser mics need it. Dynamic mics ignore it and are normally safe on it, but there is no reason to leave it on when you don't need it.

02Polar patterns

A polar pattern is the map of where a mic listens and where it is deaf. The deaf spots are called nulls. Knowing them tells you where to put the monitor wedge and which way to point the mic.

03The workhorse mics

You will meet the same half dozen mics on almost every job. Know what each is for, and you can answer "what do I put on this?" without asking.

Handle every mic as if it costs more than your phone. Hold it by the body, not the grille. Never tap it, blow into it or throw it. Put it back in its clip or case after use. The capsule is the expensive bit.

04Cables and wiring

Most mic faults are cable faults. A balanced XLR cable is the reason a mic can run 50 m across a venue with no hum. Here is why, and how to look after the cable.

Balanced vs unbalanced

Balanced means two signal wires plus a shield: XLR, or a TRS jack (tip, ring, sleeve). Unbalanced means one signal wire plus a shield: a guitar lead, an RCA or a mono jack. Unbalanced cables pick up hum and radio buzz and should stay short, under about 5 m. Mics always use balanced XLR.

Test and look after your cables

1. Test every cable before the job with a cable tester. Plug both ends in. Pins 1, 2 and 3 must light in turn, with no crossing. Wiggle the plug while testing: a flickering light is a broken joint.
2. Coil over-under. Alternate the loop direction so the cable lies flat and unwinds without twists. Never wrap it round your elbow, and never pull from the cable. Pull the plug.
3. Tag faulty cables with red tape and take them out of use. Don't put a bad cable back in the bag.
4. Repair basics. Re-soldering a plug is a workshop job. A broken XLR gets tagged and handed to the person who repairs them. At the venue, swap it.

05Wireless microphones

Wireless frees the presenter, but you are now sharing the air with every other radio user. Most wireless trouble comes from three things: a flat battery, a bad antenna position, or two systems on the same frequency.

In the B&W kit: wireless handhelds and lapels, each with its own numbered receiver.

Frequency and the law

In South Africa, ICASA regulates radio spectrum. Wireless mics mostly work in the UHF band, and the 470 to 694 MHz range is shared with TV broadcasting. Some bands need a licence and some do not, and the rules change. Check the current ICASA rules before you buy or hire for a new job type. Systems on 2.4 GHz are licence-free but share the air with Wi-Fi and Bluetooth, so they get crowded in venues full of phones and routers.

Scan, then set

1. Switch on every receiver and transmitter in the room that you can, including other crews' gear.
2. Run the receiver's scan to find clear frequencies. Pick the ones it reports as quiet.
3. Set each receiver to a different frequency, then match each transmitter to its receiver.
4. Walk the whole area with each mic switched on. Listen for dropouts.

Antenna placement and show-day rules

• Line of sight. Antennas should see the transmitter. Bodies absorb radio, so go above the crowd.
• Not behind metal. Racks, truss, lighting cabinets and LED walls block and reflect signal.
• Close to the stage beats far. Use remote antennas on a stand rather than the rear of the rack.
• Fresh batteries every show. Put in new alkalines for the day, or charge rechargeables fully. Don't gamble on a half-used set. Carry spares in a labelled bag.
• Squelch mutes the receiver when the signal is too weak, so you get silence rather than hiss. Set it just above the noise. Too high and the mic cuts out at a distance.
• Mute before you change batteries or swap a mic. The thump goes straight to the speakers.

06Mic placement and technique

Where the mic sits matters more than which mic you pick. Move the mic 5 cm and the sound changes more than any EQ. Use these starting points and adjust by ear.

Starting points

07Gain and feedback

Feedback is the howl you get when the speaker is heard by the mic and amplified again. It is a loop, and a loop only runs away when it has more than enough gain. Your job is to give the system just enough gain, and no more.

Set the gain properly

1. Fader at 0 dB (the marked "U" or 0), master down, channel on PFL (pre-fader listen).
2. Get the person to speak at their normal loud level.
3. Turn the gain knob up until the meter peaks around −12 to −6 dBFS on digital mixers, or in the green with an occasional flicker of yellow on analogue ones. Never red.
4. Switch PFL off and bring the fader up for level.

Cut the lows, ring it out

Switch on the high-pass filter (HPF) on every vocal at 80 to 120 Hz. Voices have nothing useful down there, only rumble, stand knocks and wind.

Then ring out the system, with the speakers on and the room empty:

1. Open the mics you will use and raise the master slowly until one just starts to ring.
2. Find that frequency with a narrow EQ boost, sweeping until the ring jumps out. Pull it down by 3 to 6 dB.
3. Raise the level again until the next ring starts. Cut that one.
4. Repeat three or four times, then stop. Any more and you strip the sound out of the system.
5. Back the level off a little below the last ring. That margin is your safety.

Fewer open mics means less feedback. Each time you double the number of open mics, you lose about 3 dB of gain before feedback. Mute every mic that is not being used, and tell speakers to keep the mic at the same distance.

08Mixing a mic at a corporate event

At a corporate event the voice is the product. Every word must be clear in the back row. Follow the same order on every channel and you won't get lost.

Speech vs singing

A 4-step vocal EQ

1. Cut mud, 200 to 400 Hz. A cut of 2 to 4 dB removes the boxy sound.
2. Cut harshness, 2 to 4 kHz, only if needed. Small cut, narrow. Don't take away the intelligibility.
3. Gentle presence, around 5 kHz. +2 dB. Helps the voice cut through the room.
4. Air, around 10 kHz. A small shelf boost for sparkle. Skip it if the mic is already bright.

Cut before you boost. Cutting leaves headroom and removes the sources of feedback.

Mono, stereo and monitors

• Speech goes out in mono. A centred voice reaches every seat equally. Panning one speaker hard left leaves half the room hearing a quiet voice. Send mics to the mono bus, or pan them centre on the main L/R.
• Stereo is for music. Playback and bands can be spread. Speakers and MCs stay centred.
• Aux sends feed the monitors. Use a pre-fader send, so the performer's wedge level doesn't change when you move the main fader. Give each person only what they need: their own voice, a little of the track.

09Setup checklist and fault-finding

Run the same list every job. Then, when something fails, work through the chain: mic, cable, input, channel, output.