Dynamic microphones involve a magnetic structure and a vibrating element which generates a voltage in response to sound waves. Dynamic Microphones are by far the most popular and most widely available types for sound reinforcemnt applications. Dynamic Microphones vary in price from a few pounds to several hundred pounds. Predominantly used for vocals, mics such as the famous Shure SM58 have become household names and industry standards. In recent years, new magnetic materials such as neodymium have resulted in higher performance capabilities and "neodymium" dynamic mics can be obtained for less than £100. Good examples are the Audio-Technica AT41HE and the Sennheiser e835. These mics provide a higher output and better audio quality than older mics such as the SM58 at a lower price. As well as vocals, these microphones can provide excellent results when close mic'ing instruments and even guitar cabs. They are poor for mic'ing up stage show and choirs, or in places where the sound source is more than six inches away from the microphone
Condenser Mics: work on the electrostatic principle and in general are capable of higher quality output, especially in the higher frequencies. For this reason, they are often the microphone of choice for home recording and studio work. In live use, they are extremely good at mic'ing up instruments such as acoustic guitars, and other acoustic instruments, and often used as overhead mics iin drum set-ups. Condenser microphones require a power source to drive them, usually provided by "phantom power" from a mixing desk, or via internal batteries. If your desk doesn't have phantom power, don't despair as it is now possible to buy phantom power boxes for less than £50. Condenser microphones also have the ability to pick up sound further away from the source than condenser microphones (between 12 - 18") and as such are often the microphone of choice for speeches, pulpits, lecterns etc. Condenser mics such as the Behringer B5 are excellent at a cost of only £79, with both a cardiod and omni-directional head. A local acoustic club (the Ritz Acoustic Club) uses one of these to mic up a wide range of instruments from acoustic guitars, violins, mandolins, wind instruments, squeeze boxes etc. to great effect.
Other types available are "Ribbon" mics which provide excellent sound quality, but are not roadworthy, and can be easily damaged if dropped!! Piezo-electric microphones and contact microphones are also used inside guitars and other instruments.
USAGE TYPES:
Handheld: These microphones are the standard general type of mics that have low handling noise and are used for vocal artistes, either in their hand or in a microphone stand. These are used close to the sound source and often have "proximity effect" which increase the bass response the close it is to the sound source. These are available as Radio (roving) mic systems or connected by a lead to a mixer or mixer amplifier.
Lavalier (tie-clip): Used by presenters, TV Studios, Actors, Clergy, when the microphone should be discrete or almost invisible. Used often on stage and hidden within the hairpiece or wig or masked by make-up. These small microphones are usually condenser type microphones and and are normally only used for speech purposes.
Headset (headworn): Used close to the side of the mouth, these are usually used by people who need their hands free, such as drummers, keyboard players, dancer/singers, aerobic teachers, instructors. Normally condenser in type, the better quality ones can give good results for singing, but care must be used in the placement of the mic and eq to stop "popping" sounds.
RADIO SYSTEMS
Setting up your PA for a Live Gig
The following example is based on using a Behringer SL2442FX-Pro Mixing Desk, 2 x Mackie SRM450 Active Speakers and Powered Monitors
GETTING CONNECTED AND TESTING SYSTEM
Get a good position for your desk and set up main speakers on stands. Connect main power leads to desk and speakers (do not turn on yet). It is important that the desk and speakers are connected to the same power source to help overcome problems with earth loops (low hum).
Connect cables (XLR microphone type) from the main outs (left and right) on the desk to the input sockets on the back of the speakers.
Check volume controls on speakers are set to 12 o'clock, and switches are set as you require, (normally low cut OUT and Contour IN). Do not turn on speakers yet.
Turn on power to the mixing desk, make sure All Sliders are down and all channels are muted by pressing Mute buttons on each channel, Yellow LED comes on when channel is muted. Then go to speakers and turn the power on. Turning the speakers on last, stops any "thumps" caused by turning the mixer on afterwards.
Now check that the system is working by connecting the first microphone to Channel 1 via the XLR socket, ensuring that the channel is still muted before putting the XLR plug in. Set the trim for that channel to 12 o'clock. Push IN the PFL/Solo button above the main slider (just above the talkback knob). The green PFL (Pre Fade Listen) light should be lit next to the button. This will enable you to set the levels for each channel to get the optimum signal into the desk without distortion or "clipping". Now press IN the SOLO button on Channel 1 (red clip light is now lit), Take the microphone close to you mouth and say those famous words "One-Two" quite loudly, whilst watching the main output LEDs. There should only be one line of LEDs showing as you speak (this shows you that you are level setting via PFL). Set the level by moving the TRIM knob for that channel until you get a line of all green LEDs with one or two orange when you are at the loudest level for that particular microphone. If the LEDs move into the red section for any length of time, you will get distortion and more importantly clipping which is harmful to the amplifiers in the Speakers as well as the audience.
Set the EQ (blue to knobs) for Channel 1 as follows: High 0, Mid -2, Frequency 1k7, Low -3, also press IN the low cut switch at the top of the channel. (this may not be the optimum setting but should get you somewhere close. You also have the overall EQ to assess and have the graphic to use, more later)
Now press IN the MAIN button next to the slider and move the Master Slider to about -5Db, and then slowly raise the slider for Channel 1 whilst still speaking through the microphone….. A quality microphone sound should be apparent from the speakers and a warm glow should spread through you body as you are now two thirds of the way towards getting a good sound.
You may at this point want to check reverb settings etc. But I would suggest setting up the rest of the system first before proceeding any further, as this is just to test that the system is working satisfactorily.
Now connect the other microphones etc to the desk, marking on the desk (via white insulation tape) what is in each channel. It is good to have a numbering system that you keep to, and as such you can leave the settings on the desk from one gig to another, saving time at each set up.
Connect the Foldback Monitors or monitor amps to Aux1 send and Aux2 send if you are having a two way monitor mix. Ensure that the PRE button is pressed in on each channel. (this ensures that the AUX 1 and 2 signals are sent to the monitors before the channel fader, so that any changes to the channel faders do not effect the level of the monitors)
Slide the master fader down to bottom and with the microphone in channel one, say those immortal words "one-two" whilst turning up the MAIN AUX SEND 1 and 2 knobs (just above SUB 1 Slider). You should now hear sound emanating from the monitor speakers only. Set a sensible level below feedback level, then raise the main slider back to -5Db and you should have sound coming clearly from both the main speakers and the foldback monitors….an even warmer glow! NOTE: don't set the microphone levels at the point where they are nearly feeding back, but set the levels a good bit below, so that you have "headroom to manoeuvre". You will find that as you add microphones, the point where feedback occurs gets lower and more critical. Also remember that feedback problems are more likely caused by the foldback monitors rather than the main system, so adjustments to the levels of AUX1 and 2 will normally resolve the problems. Other Vocal Mics can be set similar to Channel 1 as a starting point, and adjusted at sound check time Connect Keyboards and other DI's such as bass in the same way, except start with the trim completely off, and with the solo button pressed in, raise the trim until level is correct. Keyboards, CD Players often give out big signals so beware, and some DIs from the back of keyboard and bass amps are the same. Sometimes the only solution is a DI box with "pads" to put between the instrument and desk. EQ for keyboards are normally flat on the desk, but with the Low Cut Button OUT to get those low frequencies. In fact the only connections where the Low Cut button should be OUT is normally the Bass Drum, Bass Guitar and Keyboards. In some venues with bass heavy frequencies, I.e. wooden floors, stages etc. these buttons can be pressed in to remove a muddy sound.
THE ART OF EQ
Each Channel has three bands of EQ, with a useful sweepable Mid EQ so that specific mid frequencies can be cut or boosted for each input. There is a 9 band graphic EQ to help improve the overall sound for the venue, remember that cuts and boosts in this graphic will also effect each individual channel. NOTE: It should never look like a "smiley face", only bad DJ's do this to compensate for their poor equipment and their desire to damage the public's ears. Remember that all cuts in the graphic will reduce your overall volume and all boosts will increase your overall volume. There should therefore be some sliders both below and above the centre point of the graphic. There are normally some cuts around 1k,a small boost at about 3 -4 Khz, a small boost at about 250, often a cut at 63Hz and often cut at the highest and lowest frequencies. A good idea is to play a quality CD through the system and moving each slider from maximum cut to maximum boost to help you visualise each band and the effect it has on the overall sound .
Here are some suggestions for Drum Eq, Bass, Guitar and Vocals. The best thing is try them out with your system and you'll see what works best.
Kick Drum EQ 1. Boost 35 - 80 Hz for more power on the bottom end 2. Cut 250 - 450 Hz to eliminate the boxy sound 3. Boost 2.5K - 7k for more of the sharp attack
Snare EQ 1. Boost 150 - 300 HZ to fatten it up 2. Cut 500 - 1000 HZ eliminate low end boxiness 3. Boost 5 - 7 KHZ to make crisper Cut to give distance 4. Boost 8 -15 KHZ to add snap
Tom EQ 1. Cut in 300 - 800HZ 2. Boost around 240HZ For more body on the rack toms 3. Boost 80 - 100 HZ For more body on the low toms 4. Boost 4 - 6KHZ For sharper attack 5. Boost 8 -12.5K For more high end snap
Hi Hat EQ 1. Roll off everything below 300HZ 2. The fundamental freq. Is 400 - 1000 (600 to 800) 3. Boost 8 -12 K for more brightness
Overhead EQ 1. Roll off from around 150 Hz on down 2. Cut in 400 Hz area 3. Cut at 800 Hz for a tighter sound 4. Hi Shelf 10-12.5 KHz for brighter airy sound
Bass EQ 1. Mud generally happens in the 200-300 Hz range, cut just a little if bass lacks definition 2. Roll off from around 80 - 50 HZ on down to tighten up the bottom 3. Boost between 100 and 200 Hz if bass sounds flat or thin 4. Boost between 500 Hz and 800 Hz for more string pluck and high end definition 5. Boost between 2.5 and 5 kHz accentuates the attack, adding a little brightness
Guitar EQ 1. Roll off below 100 Hz to get rid of any bottom end that is not needed 2. Boost between 120-250 Hz adds warmth 3. Cut from 250-500 Hz if it sounds boxy 4. Add mids from 900Hz to 3.5 kHz for clarity 5. A boost at around 4 -7 kHz can add some bite
Acoustic Guitar EQ 1. If the sound is too boomy, cut somewhere in the 80 -200 HZ range. Cutting around 300HZ may help as well. 2. Boosting a little at 700HZ - 1.2KHZ for more of the resonant sound of the body of the guitar. 3. Boosting from 7-10KHZ will give you a brighter edge. 4. The pluck or sound of the pick on the strings is around 10 K
Acoustic Piano EQ 1. Boost around 3 K gives a piano more cut or edge 2. Boost at 12k for more airy sound.
Vocal EQ 1. Boost 200 HZ to add fullness 2. Boost 3K for more hard-edged stand out vocal cut between 1 - 3K softer sounding vocal. 3. Boost 5K for more vocal presence. 4. Cut 4 - 7K to reduce S sound of vocal boost to sharpen a dull singer. 5. Cut 10K to reduce S sound boost to brighten vocal. 6. Boost 15K to brighten vocal.
PROBLEM SOLVING
Feedback
Feedback is caused by certain microphones or all the microphones being set too loud, or too close or even pointing at a speaker. Feedback is based on resonant frequencies in a room and can be caused by many different issues. It can also change from sound check time to performance, as people come in and change the resonant frequencies of the venue.
To find the key frequencies in a room, try "ringing-out" the system. Do this after everything is connected and levels are set.
1. Make sure all microphone channels are open and not muted and that all microphones are switched on. 2. Set the Graphic EQ sliders flat (at 0) 3. Press FBQ (Feed Back Detection System) button in 4. Raise main slider until system starts to ring at one frequency. This frequency will glow on the individual slider of the graphic. Reduce this slider so that the ringing stops. 5. Increase the main slider further until another frequency starts to ring, and do the same. 6. This can normally be done for the main three or four frequencies. 7. The ideal situation would be a graphic setting where all frequencies ring together at the same point on the master volume slider, but this can rarely be achieved. 8. Now listen to the system and adjust tone where necessary, as it may now sound horrible due to these adjustments. At least now you know where the problem frequencies are and you can execute a compromise position between loudness before feedback and overall tone. 9. Then when you are happy raise the master volume fader again to the point of ringing and back it off anything upto about 6Db to give yourself a comfort zone and some headroom to make adjustments during the set. 10. Remember also that you should really do this with reverb switched on if you are using it, as reverbs, especially long ones can help to cause feedback. If during the set feedback occurs, it is normally because you are pushing too much foldback monitoring. 11. Also if someone only sings one song in the whole set, switch off their mic until that song, as multiple open mics interact with each other.
Sound only coming from one side of the PA
As with all faults such as this, take a logical attitude to diagnosing the problem.
1. Is the power turned on to the speaker on that side? 2. Is the cable connected to both the speaker and that side of the desk? 3. Is their anything plugged into the Main Inserts on the desk on that side (such as a graphic Eq), you may have the send and returns to the outboard item the wrong way round. 4. Is anything on the desk "panned" to produce sound only through the left or right speaker 5. Take the lead from the working speaker and plug it into the non working speaker. If it doesn't work, you have a speaker fault. 6. If it does work, now move the desk end across to the other output (left or right) if this works, you have a cable fault. If it doesn't work you have a desk fault. If you had a desk fault such that only one side of the desk is operating, (say the left side) then just pan everything on the desk to the left and run a cable from one speaker to the next speaker (daisy chaining). You will have the same output and quality, but it will just be in mono!
CAN'T GET THE VOCALS ABOVE THE REST OF THE MIX WITHOUT FEEDBACK
Turn everything else down, bring the master fader down a little to give you more headroom and increase the vocals.
IT ALL SOUND A LITTLE MUDDY
If you think it is because of EQ, the problem will be with the bass and low mid areas, turn these down on the graphic and listen to the results. You may be playing in a very reverberant room, so reduce or even turn off the reverb on everything except the main vocal. Change to a short delay instead of reverb
SIMPLE CONSIDERATIONS
Always set the speakers up in front of the band at a height that allows the Horns to pass just over the top of peoples heads, as High frequency is very directional and can be stopped by the first row of the Audience, enabling all you frequencies to get to the back of the room. In a small venue, keep the drum volumes low, or just mic the snare and the kick drum, or you'll be chasing the mic volumes up to such a level that your audience will walk out. Remember vocal mics will pick up everything behind them.
When singing through a dynamic mic (SM58s etc), get up close, that is what their designed for. a) you guarantee a better vocal signal at the desk, b) you help to mask out other stage sounds through your mic when you are singing and c) your voice will sound much richer as dynamic mics have a proximity effect which increases bass when close to them.
You can't hear your sound close to the speakers, so one of you needs to go back 10 metres or more during the sound check, to check the overall tone.
