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(Hints and Tips)

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If you have any hints, tips or other PA wisdom that you would like to suggest for inclusion on this page, please email me (or put your suggestion in a comment on the blog associated with this site). Minor alterations may be made to accepted items, to suit the general style of this site. Contributors will not be identified on this page unless they request to be. Many thanks to all our contributors.

Please note that some items on this page do not fall neatly into the section headings, so you might want to look at two or more sections. For example, tips about the connection of a cable to a microphone might be found under 'Cables', 'Microphones' or 'System Assembly and Interconnection'. (If anyone can think of a better way to organise them, please let me know!)

My apologies if you are offended by the seemingly obvious nature of some of the items. However, it can be useful to be reminded even of the obvious, and some less experienced engineers than yourself might find them them helpful! Please remember that these 'proverbs' are just opinions on what is (or is not) good or useful practice. They may need adaptation to specific circumstances, and other opinions may differ.

"What really gets me into trouble is not what I don't know, it's what I know for sure, but just isn't so." − Mark Twain.

Contents

General

  1. Never just assume that anything is going to operate as it should at the moment it's needed, without having checked it first. Equipment goes faulty, cables get connected incorrectly, controls get misadjusted. Always test everything, well before the event starts, to give plenty of time for correcting (or working around) any problems you find. [See Rig check, Line check and Sound-check − Ed.]
  2. Once equipment is unpacked, and especially during an event, keep all food and drink well clear of it − and make sure everyone else does too. This is especially important for equipment such as mixers and graphic equalisers that have lots of sockets and/or slots for slider controls. Anything that gets into these is sure to cause problems sooner or later.
  3. The better packed your equipment is, the less likely it will be to get damaged during transit. Good quality flight cases are expensive, but so are repairs − and inconvenient too.
  4. If guitarists need to plug-in or unplug an instrument cable from a guitar without first turning down their amplifier, the noise created can sometimes be significantly reduced if they first grasp an earthed metal part of the jack plug (i.e. one that connects with the sleeve of the plug) and then touch the metal sleeve or nut of the jack socket with a finger of that hand, maintaining contact until the plug is fully in or out and taking care not to touch the tip of the plug. If the socket has no accessible metal parts, then instead of touching the socket with a finger use the other hand to touch an earthed metal part of the guitar (e.g. the pick-ups). (As an alternative, self-shorting jack plugs are now available.) However, these methods may not be effective in the case of instruments that have a built-in pre-amp whose battery-power is switched by the insertion/removal of the jack plug. [Ideally, of course, a guitarist should indicate to the sound engineer to mute the relevant channel on the mixer, before unplugging any cables, but that will only prevent unwanted sounds from the FOH and monitor speakers − not (usually) from the guitarist's backline − Ed.]
  5. To help keep on good terms with hire companies, always normalise their equipment before returning it to them.
  6. When cleaning CDs, always wipe in straight lines from the centre outwards (this minimises the effect of any minor abrasion caused by the cleaning). And if cleaning to try to correct a problem with a particular track, remember that track number 1 is the innermost track on the disc.

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Microphones

(Also see the Microphones page.)

  1. Always use the appropriate kind of mic for the job (see the microphone selector).
  2. After speakers, this is the part of the system that will make the most difference, in terms of sound quality, so don't compromise. In general, avoid budget types. Only use high-impedance or unbalanced types if essential − they require suitable connection arrangements to avoid sound quality problems.
  3. Although capable of a better quality sound, condenser mics can be more prone to damage by rough handling. So for rough stage vocals use, use a rugged good quality dynamic mic such as the Shure SM58, and only use condenser mics where really necessary, such as for drum kit overheads.
  4. To avoid the embarrassment of flat batteries, use phantom powered condenser mics and DI boxes rather than battery-powered ones. (Some are capable of being powered either way.)
  5. Don't test mics by blowing into them or tapping them, as this can cause damage. Speak or sing into them instead. The spoken words "one", "two", "test" and "check" are 'tried and tested' words to use. When adjusting the mic channel EQ, listen to "one" to adjust the bass, "two" and/or "test" to adjust the treble, and "check" to adjust the mid-range frequencies. Alternatively, if a mic needs to be checked during an event and speaking into it would be inappropriate, lightly scratch the basket of the mic with a fingernail.
  6. When using multiple hand-held radio mics, or if wired mics need to be moved around on the stage (or are liable to be taken off their stands and replaced on different ones by vocalists!), identify each mic with a different colour of self-adhesive tape − stick a piece of the same coloured tape against the relevant fader of the mixer, so you can readily keep track of which fader controls which mic. Wrap a band of the tape around both ends of the held part of the mic, as either end may be at some time obscured by the performer's hand.
  7. Encourage performers in correct microphone technique, such as holding the mic at an appropriate distance for the particular use, and at the correct height and angle. (However, don't forget the visual aspect − there's little more frustrating to an audience than never being able to see the performer's lips, even if the sound is superb − especially when close-up video is in use.)
  8. Try to discourage vocalists from wrapping their fingers around the basket of the microphone, as obstructing the entry of sound into part of the microphone can significantly alter its directional characteristics and may make feedback more likely and/or cause undesirable tonal colouration.
  9. Try to discourage vocalists from holding radio mics at the very bottom end, in the case of types that have a projecting aerial there, as this would reduce the effective power of the transmitted radio signal, and so increase the likelihood of reception problems.
  10. Unless essential, avoid wired mics that have on/off switches. Some performers have a habit of switching them off accidentally (or deliberately and then forgetting they've done so), or leaving a mic switched off for a later performer who expects to find it switched on.
  11. Correct placement of mics is often critical to achieving the best results, especially when close-miking acoustic instruments. When deciding where to place a mic, it's worth considering that the mic will 'hear' much the same sound as if you placed your ear in that position, pointing in the same direction. (But when trying this, beware of high sound levels.)
  12. When miking-up a multi-driver instrument cab, listen to the cab first to check that the driver you choose to mike-up isn't a dodgy-sounding one. (Again, beware of high sound levels.)
  13. When a mic is used with a tight-fitting mic clip, be aware that the pressure of the clip can cause the XLR latch to be released as the mic is removed from its stand by the performer, with the possibility that the XLR plug can then lose electrical connection with the mic, or even fall out completely. If this looks a possibility, be sure to place the mic into the clip with the XLR latch-release button in line with the slot of the clip, and ensure that the performer knows to replace the mic similarly.
  14. Inferior quality windshields can seriously damage your sound!
  15. When using condenser mics with phantom powering, check that the voltage of the available phantom power is correct for the microphones before connecting them.
  16. When using several condenser mics and/or DI boxes with phantom powering, check that the the total current demand of all the phantom-powered devices connected to the mixer does not exceed the total phantom power current available from the mixer.
  17. If using a ribbon mic, it is best to avoid applying phantom power to it if at all possible, as a fault in the mic cable can easily cause the mic to be seriously damaged.
  18. When using a ribbon mic, never blow into the mic, as this is almost certain to cause serious damage to it.
  19. If a mic is suspected of being faulty, don't put it back in the box with the others, to be taken out again and be used another time. Put it separately (preferably marked in some obvious way) until it has been checked and repaired.
  20. When attaching a lavalier mic to its user's clothing, get them to tilt their head fully forwards and ideally clip the mic at a height about 2 cm (1 inch) below the point on their chest where their chin touches it. If the user is to be facing forwards for the majority of the time, then preferably clip it at a central position. If the user is to be predominantly facing towards one side (as in some interview situations), then clip the mic at that side of centre.
  21. If a new mic has to added, or a faulty one replaced, during a performance, it is often inappropriate for it to be tested in the normal way, by someone speaking into it. Even if the mic is not routed to FOH during the test, seeing a person speak into it can be a visual distraction. In such cases the basic operation of the mic can be confirmed by activating the PFL on the relevant channel, turning up the headphones level control, and listening for the ambient sound picked up by the mic. (It may also be necessary to temporarily turn up the channel gain control, depending upon the sound level in the vicinity of the mic.) The only problem with this is that it doesn't confirm that you really are listening to the new mic (it may have been plugged into the wrong channel on the stagebox!). So if the mic is being placed by someone other than yourself, a better approach is to have them lightly scratch the basket of the mic with a fingernail, while you listen for this distinctive sound via the channel PFL. The assistant can be given a 'thumbs up' signal when this check is completed.
  22. If a performer insists on swinging a mic on its cable, do not rely on the latch of the XLR connector to secure the mic to its cable. Use only a heavy-duty mic cable in good condition, and check the tightness of the XLR's cable clamp. Wrap plenty of gaffer tape around the mic, the connector and at least the first 150 mm (6") of cable (taking care not to tape over the XLR latch release button!). Also, to help ensure that there is no possibility of the mic or its cable striking another performer, crew personnel, or object, securely attach some coloured tape to the cable to indicate the furthest distance from the mic that the cable can be safely held by the performer, when swinging it.
  23. When using microphones some distance from the sound source (for example in the case of drum kit overheads, choir mics or rifle mics), and monitor speakers are in use, take care to avoid the sound from those speakers being picked-up by the mics along with the wanted sound, as that can degrade the FOH mix. This can be a particular problem with drum kit overheads, because most dummers like their monitors loud. Consider using headphones or IEMs instead. Otherwise, minimise problems by using positioning and directionality of both the mic(s) and the monitor(s), and keep the monitor(s) levels down to the minimum acceptable.
  24. When an acoustic guitar doesn't have a built-in pickup, close-up use of a stand-mounted microphone is best avoided if the guitarist is standing, because even slight movement of the guitar body relative to the mic can significantly affect the nature of the picked-up sound (as well as its level). In a live situation when close-miking of a guitar is required, the guitarist should be seated (and should take care to hold the guitar in a fixed position) or else a miniature gooseneck mic, or a suitable temporary pick-up, should be attached to the guitar. (In a studio recording situation, use of a stand-mounted mic may be suitable if it can be placed at a sufficient distance from the guitar to make any small changes in position and distance less significant.)

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System Assembly and Interconnection

(Also see the System Assembly page.)

  1. When deciding on the location of the front-of-house mixer, don't assume that a position on the centre-line of the venue will give the best listening position. Although this is often the best choice, sometimes sound reflections from surfaces (especially curved ceilings) can cause problematic cancellations at a central position, so a position slightly to one side may be preferable in such circumstances.
  2. For rapid location of a desired channel during an event, when cabling-up the system assign the stage signal sources to the mixer channels in the same order that they are positioned across the stage (as viewed from the mixing position). As it's usually helpful to keep the channels used for vocals next to each other, assign those channels (in stage position order) first, followed by the instrument channels (in stage position order). [Or, use a standard ordering such as the one shown here − Ed.]
  3. To avoid dangerous and/or expensive mistakes, don't use the same kind of connectors for different purposes in the same system. In particular, beware of multiple uses for Socapex connectors (mains power, balanced audio lines or amp-to-speaker connections) and for XLRs (balanced audio lines or low-power amp-to-speaker connections). This is especially important for touring systems, and even more so when unskilled people are assisting in assembling the rig. (If such mixed use is unavoidable, ensure that all the relevant connectors are very clearly labelled.)
  4. If it is desired to extract a line level signal from one or more individual channels of a mixer, e.g. to feed IEM transmitters for individual performers, or for multi-track recording purposes, and there is no 'direct out' facility, you can use the channel 'insert' facility of your mixer (if it has that!). For each channel of interest, you need to make (or otherwise obtain) a special cable, consisting of an unbalanced screened cable terminated in a 3-pole ("stereo") jack plug. The screen of the cable is connected to the sleeve of the plug (as usual) but the 'signal' (hot) conductor is connected to both the tip and the ring of the plug. This plug then connects into the 'Insert' socket on the relevant mixer channel; the link between tip and ring connections prevents the signal path through the mixer from being broken. The other end of the cable is terminated normally in whatever kind of connector is needed for the equipment you are feeding the signal into. The internal wiring of the 'Insert' socket on some mixers supposedly avoids the need for such a special cable, allowing a signal to be extracted by inserting an ordinary 2-pole ("mono") jack plug only partially into the socket − just to the first 'click'. However, this is not recommended because in a large system it would be too easy to forget which plugs are deliberately partially inserted − it would be all too likely (especially for some other 'helpful' soul) to think that the plug had not been properly inserted, or had subsequently taken a tug on its cable, and push it fully in. The consequences would not be good.
  5. Most tape, CD, and DAT recorders reproduce their input signals on their output connections when in record mode. Therefore, when such a machine is connected to a mixer for both recording and playback, there is a likelihood of an electrical feedback loop being created which can seriously damage speakers, etc. So unless you are sure your machine does not have this facility, or has a foolproof way of disabling it, always use the designated 'playback' inputs on the mixer (which usually do not feed to the 'record' outputs − but do check this!), rather than using normal channel inputs. (Alternatively, use an auxiliary output on the mixer, rather than the 'record' output, and be very careful not to turn up that Aux Send on the channel(s) used for playback. For a mix the same as the main mix, use a post-fade auxiliary and set all the required Aux Sends to 3 o'clock − or to '0 dB' if marked.)
  6. Be aware that most mixing desks do not isolate the XLR (mic) input of a channel when a jack is inserted into the channel's line input. So it's always best to remove the plug from the mic input when the line input is being used, to avoid the possibility of interference with the line-level signal from any unexpected signal or connection on the XLR cable (especially if it routes to a stagebox). [Of course, the converse also applies − Ed.]
  7. To assist in balancing Left and Right speaker levels, use the same length of speaker cable for both Left and Right speakers − even when the Left and Right amplifiers are located together and closer to one side than the other.
  8. Consider using a 2-channel amplifier configuration, with separate 'Left' and 'Right' connections from the mixer, even when you're mixing in mono. That way, if an amplifier fault or an amplifier feed fault develops during an event, you'll probably only lose half of the system rather than all of it.
  9. When not a safety hazard or too unsightly, coil any excess length of stage cables at the source (e.g. mic) end of the cable. This avoids the stagebox area being cluttered-up with all the spare cable (which can make later access difficult) and makes those last-minute changes of mic location much easier to cope with − especially when the cable run to the stagebox has been taped down. If for some reason the coils can't be at the source ends, make them a metre or so away from the stagebox − and use a releaseable cable tie around each coil to prevent them getting jumbled.
  10. When connecting an unbalanced instrument feed to a mixer or stagebox, always use a DI box. Don't be tempted to use an in-line adaptor to convert from an unbalanced jack to an XLR, as these don't provide a balanced signal to the mixer and can cause serious damage to instruments if the mixer has phantom powering switched on.
  11. If your speaker cables have jack plugs at the end that connects to the speakers, don't plug-in or unplug the jack while the other end of the cable is connected to an amplifier that is switched on. (As the plug goes in or out, the sleeve contact inside the socket could bridge across the insulation between the sleeve and tip of the plug, short-circuiting the amplifier output and damaging the amplifier.) In any case, it is not recommended to connect or disconnect speakers from amplifiers that are switched on. − Also see the next tip.
  12. Unless your speaker cables have connectors with protected contacts (such as Speakons) at the speaker end, don't leave that end of the cable unplugged while the other end of the cable is connected to an amplifier that is switched on. (The 'signal +' (hot) pole of the plug could touch onto earthed metalwork, short-circuiting the amplifier output and damaging the amplifier.) − Also see the previous tip.
  13. Preferably, avoid connecting speaker outputs of backline amplifiers to DI boxes. (Instead, use a mic on the speaker, and/or use a line-level output into a DI box.) If you must do this, only use a DI box that has a specifically-designated speaker input, only use a passive DI box, use a correctly-wired speaker cable to make the interconnection and take great care to make sure that the DI box's earth lift switch is in the 'LIFT' position before you connect the amplifier to it. [Also see the previous two proverbs, and see Emulated line output − Ed.]
  14. When assembling large systems, keep an eye on mains power requirements. As a rough guide, amplifiers providing a total of 2 kW output power is the maximum that should be supplied through any one 13 Amp socket outlet of the building's fixed electrical installation.
  15. When connecting several speakers to one channel of an amplifer, take care not to go below the minimum load impedance catered for by the amplifier.
  16. When connecting an unbalanced XLR output of a mixer to an unbalanced XLR input of an amplifier, be aware that equipment differs in which pin of the connector is used as the 'hot' connection. Most British equipment uses pin 2 for the 'hot', but some older US equipment uses pin 3. So, if these types of equipment are being interconnected a special cable will be needed to make it work. N.B. Pin 1 is always used as the 'earthy' (screen) connection.
  17. When connecting a mic cable to a microphone, be sure that the XLR is pushed in hard enough for the latch to click into place (greater pressure is needed for XLRs having a rubber sealing ring). This is especially important if the mic is to be removed from its stand by the performer, and/or is likely to be treated roughly. Plugs falling out of mics during a performance is not good news.
  18. When running out audio XLR-to-XLR cables such as mic cables or feeds to amplifiers, it can be helpful to remember that the pins of the connectors 'point' in the direction of the signal flow. So, the end of the cable with a female connector needs to be at the 'source' end of the run, and the end with a male connector at the 'destination' end. N.B. DMX lighting control cables are the opposite to this!
  19. When running out an induction loop cable, avoid including the stage within the area of the loop if at all possible. This will reduce the likelihood of magnetic feedback problems caused by guitar pick-ups etc. picking up the field from the loop. (Note, however, that the field is not contained entirely inside the loop area − there is some degree of 'overspill' − so the further the loop area from the stage the better.)
  20. Wrapping a mic cable a couple of turns around the vertical pole and boom arm of a mic stand is a good way to keep the cable tidily in place (when your stand isn't supplied with the nice clips for that purpose). However, don't do this (still less use the nice clips!) on a vocal mic stand unless you're sure that the vocalist will not want to remove the mic from its stand and hold it, at some point during the performance.
  21. When a stereo source is to be connected to a stereo rig, the ideal would be to use a fully-featured stereo input channel on the mixer. However, many professional mixers do not have these (e.g. so-called 'Tape/CD' inputs often have very limited EQ and Aux Send facilities). In such cases it may be necessary to use two normal mono channels of the mixer, one for the Left signal (panned hard left) and one for the Right signal (panned hard right). When doing this it is necessary to ensure that the channels are set-up identically, and that any subsequent adjustments are made to both of them.
  22. When a stereo source is to be connected to a mono rig, it is necessary to decide whether or not the Left and Right signals must be summed, or if just one of them can be used. Often, for recorded material the signals must be summed (because of hard panning in the recorded mix), but for stereo instruments just the Left channel is used. (Many stereo keyboards provide a summed mono output if only the Left output jack is used − but if the musician notices this there may be some explaining to do!) If summing is required, then if the mixer has an available stereo input with sufficient features this may be used provided that the Left and Right busses are summed (e.g. by routing the busses to the same mix, or by using a Mono output of the mixer). If a suitable stereo input is not available then a 'Y-splitter' may be used 'in reverse' to combine the two signals by direct connection of both of them to a single mono channel of the mixer, provided that the signals do not come from very low-impedance sources (such as headphone outputs). There is normally no problem in making a direct connection of line-level Left and Right outputs of semi-professional or consumer-type tape and CD decks. If there is any doubt about this then it is necessary to use two mono channels of the mixer, one for the Left signal and one for the Right. The two channels must be set-up identically (routing both to the same bus), and any subsequent adjustments must be made to both of them.
  23. Problems (typically intermittent operation, or distortion) are sometimes experienced on particular mixer channels, due to oxidation of the normalling contacts of the Insert jack sockets. (This is more likely to occur if the contacts have been held separated for a very long period of time, by a plug remaining inserted.) Until the socket is replaced, the problem can be solved by use of an insert lead with its 'send' and 'return' connectors at the far end linked together, or by use of a 3-pole jack with its tip and ring terminals connected together (and no cable attached).

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Mixing

(Also see the Intro for Mixing Engineers page and the Mixing Facilities page.)

  1. Always set the channel gain controls first, using the mixer's built-in level indicators. Note, however, that a subsequent large change to the channel EQ settings will often change the overall level of the signal. If an EQ boost significantly increases the level, it may be necessary to decrease the setting of the channel gain control in order to restore the required headroom (which in turn may necessitate re-adjustment of the channel fader).
  2. After the initial rig check, set up monitor mixes before the front-of-house mix, as this enables the total on-stage sound level to be assessed and controlled early on. Also, when the band are desperate to start their rehearsal (because of delays to the set-up schedule, or because insufficient time has been scheduled for a rehearsal after the sound-check), having the monitors set up first will enable the band to start rehearsing sooner.
  3. It is common for vocalists to sing louder, and for musicians to play louder, when the audience are in place for the event (as compared to how they performed in the sound-check). So it can be helpful to set the gain controls a little on the low side during the sound-check, to accommodate the higher levels expected later.
  4. It can sometimes be difficult to see which switch-buttons on a mixer are 'In' and which are 'Out' − especially in poor lighting conditions. To help with this, some mixers (e.g. Mackie) have a line drawn around the buttons (e.g. a white line on grey buttons). If you can see the line above the mixer panel then the button is 'Out'; if you can't then it's 'In'.
  5. To avoid overloading the mixing amp of the desk, when creating mixes start with the faders at their '−5dB' positions (approx 60% of travel), then vary them from there − mostly with reductions. If during sound-check you end up with any channel faders exeeeding '+3 dB' (85% of travel), more than 10% of them exceeding '0 dB' (75% of travel) or more than a quarter of them exceeding '−5 dB', then increase the main fader setting and back off all the channel faders by a corresponding amount. (See also the next proverb.)
  6. To maintain a satisfactory signal-to-noise ratio from the the mixing amp of the desk, if during sound-check you end up with all the channel faders at below '−15 dB' (approx 30% of travel), then decrease the main fader setting and increase all the channel faders by a corresponding amount.
  7. Only mix in stereo when there's a real benefit (e.g. special effects) − and only when the layout of the venue is such that the majority of the audience are covered well by both the Left and Right speakers (this is very rare!).
  8. Make good use of your mixer's grouping facilities (e.g. vocals in one group, drum mics in another, guitars in another, etc.), so that the level of these sets of channels in the mix can be adjusted as a whole, using the group faders. If your mixer doesn't have a grouping facility, but has Left, Right and Mono (L+R) master faders, then by panning the vocals to hard left and the instruments to hard right you can use the Left and Right master faders as group faders (in which case of course you use only the Mono output to drive the front-of-house amplifiers).
  9. The sound throughout a venue will be different at different locations − and not just louder nearest to the speaker stacks. What's more, the sound will often change significantly when the audience enters − there will be less natural reverb and the high frequencies will tend to be reduced towards the back of the venue as they are absorbed much more by the audience than are the bass frequencies (see grazing effect). So familiarise yourself with the sound in different parts of the audience area, and during the event be aware that members of the audience are not all hearing the same sound as you − especially if you are mixing from the very back of the venue.
  10. When setting the individual channel EQs during sound-check, it can help you to focus on the sound via the channel to be adjusted if you first temporarily raise the level of that channel in the mix. After setting the EQ, restore the channel fader to its correct position (which may be slightly different to its previous position, because of the effect of the changed EQ) before moving on to the next channel.
  11. One possible way to set sweep EQ controls is as follows:
    • After setting the Low (LF or Bass) and High (HF or Treble) controls as required, make sure that the cut/boost control(s) of the sweep EQ is set flat (i.e. to '0', 12-o'clock).
    • Now listen to the sound and decide what you don't like about it most of all.
    • Next set the cut/boost control of the sweep EQ to give a large amount of boost (about 10 to 12 dB) and set the Q control (if you have one) to about 2.5.
    • Set the Frequency control to minimum, then slowly rotate it up to its maximum setting, noting the position that makes what you don't like about the sound (as noted above) become significantly worse. When you have swept the whole range, return the Frequency control to that position, and return the cut/boost control to '0' (flat), so that the original sound is obtained.
    • Now slowly rotate the cut/boost control anti-clockwise until the best sound is obtained, in conjunction with adjustments to the Q control (if you have one).
    • Finally, make any necessary re-adjustments to the High and Low controls (and to other sweep EQ controls on that channel, if it has any others).
    • If you have other sweep EQ controls on that channel, proceed to adjust them in like manner.
  12. When using a multi-amped system (i.e. separate amplifiers for each frequency range, e.g. bass, mid, high), keep the main graphic equaliser flat until the crossover(s) have been properly set and the amplifier levels for each range have been properly balanced.
  13. When graphic equaliser sliders have a very small travel (35 mm or less), an adjustment of just one or two mm can have a very significant effect on the sound. Check the 'Range' setting, if there is one (e.g. ±6 dB or ±12 dB).
  14. Remember that the FOH graphic equaliser affects the total mix, so don't be tempted to adjust it based on the sound of a single channel (unless it's playing a CD that you are very familiar with the correct sound of − in which case first be sure that the channel EQ is flat!). The only proper way to set up an FOH graphic is using an audio test CD having test tracks for each frequency band of the graphic, and checking the sound level of each band at several places in the venue using a good quality sound level meter (this takes a long time!) − Again, first be sure that the EQ is flat on the channel used for the audio test CD! [Analysis tools are now a popular alternative method for FOH. Monitor graphics are often best set up using the ringing out method − Ed.]
  15. Treat any comments from the audience judiciously. Enquire where abouts in the venue the person was located, and remember that tastes differ from person to person.
  16. Get to know your mixer well − e.g. which Aux or Effect sends are pre-fade and which are post-fade, and whether they are pre-EQ or post-EQ.
  17. Activate the channel Low Cut switches on all channels with no wanted deep bass content − especially on microphone channels used for vocals, strings, drum overheads, etc.. This reduces pick-up of unwanted bass leakage, handling noise, etc. on those channels. [However, check that these switches are not activated on channels with wanted bass content, such as kick drum, keys, bass, etc. − Ed.]
  18. Keep alert, even when things seem to be going smoothly. The unexpected can and does happen, and a rapid response is sometimes required.
  19. If you are using a channel input for the return from an effects unit, be very careful not to turn up the relevant effect send control on that channel. If you do, the resultant electrical feedback could seriously damage your speakers. Preferably, mark the control in some way, as a reminder.
  20. Once a satisfactory mix has been established, and changing circumstances then require further adjustments to be made, take care to make only small adjustments (in the first instance). All the hard work done during sound-checks and rehearsals can be rapidly undone by a few large changes here and there.
  21. Remember that ambient noise sources (such as HVAC, or sounds from outside the auditorium) may have a significant impact on the overall signal-to-noise ratio perceived by the audience − especially in low-level applications such as speech amplification. When the PA system signal-to-noise ratio is satisfactory but the perceived signal-to-noise ratio is poor, and a further increase in amplified sound level is not possible (e.g. because of feedback), steps may have to be taken to reduce ambient noise levels.
  22. When using a monitor mixer, with mixes created using the auxiliaries, use post-fade auxiliaries. This enables the channel faders to be used as overall level controls for the individual sources, allowing convenient and rapid adjustment of a source in all the mixes simultaneously when required (e.g. due to feedback or a sudden change in source level).
  23. When using a monitor mixer, patch graphic equalisers into the inserts of the mixer outputs (usually the auxiliary sends) rather than routing the outputs via the graphic equalisers. This allows the effect of the appropriate graphic equaliser to be taken into account when monitoring a particular output using its AFL (but check that the AFL monitors the signal post-insert!).
  24. When using a monitor mixer, if at all possible use a listen wedge that is identical to the monitors being used by the performers, so that you get the best possible match to the sound that they hear from their monitors.
  25. When playing pre-recorded material that is routed via pre-fade auxes (e.g. to stage monitors) as well as via the channel fader, remember that if the track needs to be manually faded out then you must fade down the relevant aux send(s) as well as the fader − otherwise even with the fader fully down the audience will probably still hear the material via the monitors. (In such cases, consider having the relevant aux send on that channel switched to post-fade, if your desk has that facility.) Obviously the same applies to manual fade-ins.

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Amplifiers

(Also see the Amps & Speakers page.)

  1. Be sure that amplifiers have an adequate output power rating − at least 30% above the power input that the speakers require in order to achieve the desired sound level − to maintain headroom on signal peaks. But don't misuse the spare power by over-driving the speakers.
  2. Remember that the maximum output power that can be obtained from a particular channel of an amplifier is not a fixed value − it depends on the overall impedance of the speakers that are connected to that channel.
  3. Before switching on the amplifiers, switch on mixers, graphics, etc., and check that the amplifier level controls are set at minimum. Likewise, before switching off any other equipment set the amplifier level controls to minimum and switch off the amplifiers. [For more detailed information on this, see Switch on/off procedure − Ed.]
  4. When using a multi-amped system (i.e. separate amplifiers for each frequency range, e.g. bass, mid, high), be sure that the main graphic equaliser is flat before starting to balance the amplifier levels for each range. The only proper way to balance the amp levels is to use an analysis system or to use an audio test CD having test tracks for each frequency range, and check the sound levels at several places in the venue using a good quality sound level meter. (First be sure that the EQ is flat on the channel used for the audio test CD!)
  5. Never connect a speaker output of an amplifier to anything other than a speaker. Doing so can cause all kinds of expensive damage.

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Speakers

(Also see the Amps & Speakers page.)

  1. In terms of sound quality, this is the part of the system that will make the most difference (closely followed by microphones), so don't compromise on choice. It isn't possible to properly compensate for poor quality speakers by using equalisation.
  2. When choosing speakers, compare the sensitivity figures. This is a guide to how much sound level you will get from the speaker for each watt of power input from the amplifier, and can vary hugely between different types of speaker. Remember, however, that the easiest way for the speaker manufacturer to achieve an impressive sensitivity figure is to compromise on sound quality, so be sure to check that too.
  3. To get the best out of your speakers, be sure that they are at the correct height for the situation are that they are positioned and angled correctly. This can make a very significant difference to the quality of the sound perceived by the audience! For example, locating speakers inward from the side walls, and/or angling them slightly inwards towards the centre of the room, can help to reduce troublesome reflections from the side walls (especially in long, narrow rooms). And raising the height of the speakers and angling them slightly downwards can help to reduce the difference in sound level between the front and back of the room. (See also the next tip.)
  4. When setting the position and angle of front-of-house speakers, use the 'line of sight' method to help with the alignment of the high-mid cabs and HF horns. This is especially helpful to get an initial position, before the system is ready to be switched on and listening tests done. First stand behind (or under) the speaker to judge what area it is covering, and make adjustments to its position and angle as necessary. Then walk around the listening area, looking at the relevant speakers − you should be able to see into the speaker horns. (Remember to take into account any obstacles that might not yet be in place, such as a standing or dancing audience.) These methods work because it is the high audio frequencies that carry the intelligibility and clarity of the sound, and these travel in substantially straight lines, just like light.
  5. If you are connecting speakers of different impedance to the same amplifer, the speakers having the highest impedance will take the smallest amount of power from the amplifier (and will therefore probably produce the least sound).
  6. Configure the speaker system according to the programme material. Powerful bass bins are not required for reproduction of speech, or of music with minimal bass content.
  7. When positioning monitor speakers close to microphones, take account of the polar pattern of the microphone in order to ensure minimum pick-up of the monitor sound by the microphone, and so reduce feedback problems. For cardioids, the monitor should be on the rear axis of the mic, i.e. directly behind it. For super-cardioids use two monitors, each at an angle of 55 degrees from the rear axis. For hyper-cardioids the two monitors should each be at an angle of 70 degrees from the rear axis.

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Cables

  1. For ease of recognition, put similar markings on cables of the same type (mic cables, speaker cables, instrument cables, etc.), and store similar types together. They can be marked at the ends with coloured tape, with clip-on identification rings, or the cables themselves could be of a different colour.
  2. Don't coil cables by wrapping them around your arm − this stresses the cable and puts a twist in it at each turn of the coil.
  3. Releaseable cable ties and Velcro® ties are a real boon. Use them around cables in storage or transit to prevent them becoming tangled with each other; use them on-stage to keep coiled excess cable lengths neat and tidy. 200 mm is a good length to use for most cables. For bulkier coils (such as speaker cables), two of these ties can simply be linked together to make one (nearly) twice as long.
  4. If you plug together the two ends of XLR-XLR cables as soon as you have coiled it for storage or transit, the ends can't fall between the turns of the coil and create knots.
  5. If a cable is suspected of being faulty, don't put it back in the box with the others, to be taken out again and be used another time. Put it separately (preferably marked in some obvious way) until it has been checked and repaired.
  6. Cable faults are often intermittent, so if a cable seems to be faulty and then seems OK again, mark it as suspect and don't use it until it has been fully checked out − otherwise it may unexpectedly fail again during use.
  7. Always use proper speaker cables rated for the job − don't use instrument jack-to-jack cables or microphone XLR-to-XLR cables, as both of these can be damaged by the high current and voltage of speaker signals.
  8. It's worth investing in good quality cables − but the hyper-expensive types rarely give much added benefit. Manufacturers well-known for the quality of their cables include Belden, Canare, Klotz and Van Damme (the links are to their websites, and open in a new window).
  9. Check mains cables frequently for signs of damage, and get them promptly and properly repaired or replaced.
  10. When removing cables that have been gaffer-taped to the floor, don't pull up the cable from the floor with the tape still attached to the cable. Rather, while pulling the tape from the cable with one hand, hold the adjacent loose part of the cable down on the floor with the other hand. This will prevent the edges of the tape curling around the underside of the cable − if the sticky sides touch they are almost impossible to get apart again and the tape will require time-consuming removal from the cable afterwards by tearing or cutting, with a risk of damage to the cable.
  11. In large systems, it can be helpful in tracing cables (when you need to fix a problem or to make changes) if all cables have a unique reference number at both ends. Clip-on numbered plastic rings are available for this purpose.
  12. Don't use XLR cables that have the shell of the connectors connected to the cable screen (pin 1). This avoids the possibility of earth-loop problems being caused by the connectors at cable joints coming into contact with each other, or with adjacent metalwork.
  13. When wiring XLR connectors to make balanced cables, the name 'XLR' can be used as a mnemonic for which pin is which: pin 1 = X = Earth, pin 2 = L = Live (hot), pin 3 = R = Return (cold).
  14. The mnemonic 'Tip-To, Ring-Return' can be used to help remember the (most common) wiring of mixer TRS insert jacks. So, the signal is fed To the effect unit via the Tip connection, and it Returns to the mixer via the Ring connection.
  15. When making cables to connect from a 3-pole (stereo) mini-jack output of a laptop, MP3 player, etc., it can be useful to wire a pair of resistors into the connector(s) at the other (i.e. destination) end of the cable. This avoids the possibility of damage to the laptop or player if the hot connections of the destination end get shorted to earth while the mini-jack is plugged into a headphone output. (Such a short is only really a possibility if the destination end is a jack connector). Wire a 1 kilohm resistor in series with the Left hot connection, and another in series with the Right hot connection. This also provides protection against damage, or current-overload distortion, due to shorting Left and Right headphone outputs together, such as happens when the stereo output is wired into a single mono connector at the far end of the cable. Or likewise if the Left and Right signals are cabled into two separate mono connectors, which subsequently get plugged into a pair of commoned inputs (such as a pair of input sockets on a single channel of a DI box).
  16. When doing special things inside connectors, as suggested in the previous entry, it's wise to label the cable accordingly, to avoid confusion later. (Also because such cables may be indicated as faulty by a cable tester, even though they're wired as intended.)
  17. Keep all cabling well clear of transformer power supply units (whether of the plug-in or in-line types), as the stray magnetic field from the transformer can induce a hum current into the cable conductors. Even excess lengths of mains power cables should not be located close to such power units, as a hum current can be induced into the earth conductor of the power cables − this is more likely to cause a problem if you have any unbalanced signal interconnections. Preferably, route all 3-core mains cables directly away from power supply units.
  18. When packing away bodypack units, don't wrap the mic/earphone cable around the bodypack. These thin cables are very easily damaged, and repeated bending of the same points along the cable around the corners of the bodypack can cause problems to occur at those points.

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This page last updated 27-Dec-2010.