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If you haven't
got any gaffer tape buy some now! it can save you life later!
Carry a tool box, if you have travelled a couple of hours to an
event and any critical part of your system fails you are dead in the
water! Some tool box essentials should include:- Screwdrivers,
solder & soldering iron, pliers, wire cutters, a selection of fuses
(make sure you have the correct size and rating for your equipment),
a digital multimeter for testing leads & equipment, plastic
tyraps/cable ties (useful for suspending cables/multicores), some
white electrical tape and a permanent black marker - very useful for
identifying mixer channels and specific microphone/cable
arrangements on the night, don't use water based markers as sweat or
moisture will remove your markings and leave you confused!
P.S. if you
hire equipment from us and you suspect a problem DO NOT attempt to
repair it yourself, please contact us and we will investigate the
problem and replace or repair the equipment if necessary.
Occasionally problems arise from people not knowing how to correctly
use a piece of equipment, a simple phone call to us and some helpful
advise could have you up and running in seconds.
Make sure you
know how to operate the equipment you are hiring or using, if you are unsure
then we can assist in setting up and give you copies of the
equipment
manuals.
First things
first, make sure you have hired a big enough system to cope with
the job at hand. Too often a budget will decide the size of a PA
system, its always better to have a little too much rather than not
enough, the problem is how do you know how big a pa system you
require? Well its a tough one to answer especially if you have
never done this kind of thing before. Some things to consider
are how loud you would like it to be? what do your audience expect?
how big is the venue? how many people will be there? are you
amplifying just vocals or instruments as well?
Typically if you are
just amplifying vocals pa systems tend to be quite small and
portable and are capable of dealing with audiences of a few hundred
with only a few hundred watts, its only when you start with mic'd up
drum kits and instruments that things start to get a bit more
complicated.
PA System Power
Ratings
These days
everyone talks of PA system power in terms of 'K' or 'kW' which is
short for kilowatts, 1000 watts is 1 kilowatt. This is not
really the best way to work out how loud a system is going to be. All loudspeaker enclosures have different efficiency ratings with
the output of the loudspeaker (SPL or sound pressure level) being measured in dB (decibels).
A loudspeaker enclosure made by one manufacturer may have only half or
a quarter of the output of that compared to another manufacturers
loudspeaker, even with the same input power rating. If you
compare the following two speaker specifications you will see why
this is:
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|
A |
B |
|
RMS Power (Watts) |
500 |
500 |
|
Maximum Continuous SPL (dB) |
131 |
125 |
Both speakers
are rated at the same power input but have different outputs, you
might think that only 6dB is not much but it is the equivalent of
four times more power, therefore you would need four times as many
'B' speakers to keep up with only one 'A' speaker. So system 'A' may
be rated at 500W and system 'B' would need to be 2000W.
For every
3dB increase in output you need to increase power input by 2, and
for the human ear to notice a significant difference you would need
to increase the system output by 6dB, which is four times the power.
This may not seem too bad when you are increasing from 500W to 2000W
but if system 'A' was 2000W then system 'B' would need to be 8000W.
When you look at that in terms of loudspeaker cabinets system 'A'
would comprise of four boxes and system 'B' would need 16 boxes to
achieve the same volume level!
Another thing
to consider is 'Peak output' vs. 'Continuous output'. Peak
output is often not clearly defined or is quoted with different
percentages of distortion (THD), peak output can also be up to four
times the continuous output. If you tried to operate a pa
system at its peak output level it would probably sound very
distorted and would not last long at all. To compare systems always
look for the continuous output, this is a level that the system
should be capable of running at all night, it is also worth bearing
in mind at this point no system should be operated at its maximum
level all the time, there may be musical content which is
momentarily louder and requires more output, if your system is
running flat out already any intended peaks in the content will be
lost.
Typically when
we operate our own loudspeaker systems at most run of the mill gigs
and events (and we have recommended the system size) the system will
be capable of operating at at least 105dB (from 40Hz to 20KHz
+/-3dB) continuously at the mixing
console position towards the back of the venue with occasional peaks
of up to 115dB, you should not require much more volume than this in
reality, as excessive volume can be painful and not to mention
damaging to your hearing!
At the end of the day
get the right size system, its your performance that will suffer in
the end and you don't want your crowd going home unhappy,
there are a lot of other bands out there doing the same thing as you
so make sure you sound as good if not better than the competition.
Layout
Ensure the
PA system is laid out correctly, if you are not sure what this should
look like the click
here for a
diagram. Basically make sure the Front Of House (FOH) speakers are in
front of the performers microphones and facing away from them, this
will be the biggest help in stopping feedback! Also place monitors so
that the back of the performers microphone points at the front of the
monitor (most vocal mic's have a cardioid pick up pattern and have a
dead spot at the back), don't place your monitors at the side of the
performer. Make sure you route all of the cables away from areas
where people will be walking, this will stop you tripping up people
and stop people treading on your cables. It's always a good idea to
tape down cables that you don't want to move, but be careful, it's no
good taping down a mic cable and then trying to walk around the stage
halfway through your set!
When you come to
turn on the system start at the FX then to the mixer and then turn on
the power amps last, this way you avoid any nasty pops and clicks that
can be damaging to speakers. When its time to turn off start at the
power amps and work your way backwards. After you have turned on all
of the equipment now is a good time to check that it is all working
ok, its good practice to play back some music at a low level to make
sure you can hear it coming out of all of the speakers. If you are
running an active system make sure you have got the right frequencies
coming out of the right speakers, 500W of bass will probably destroy a
HF or compression driver instantly.
If you are doing
the mixing or someone is doing it for you then try and get a position
in front of the stage and preferably somewhere central, its no good
mixing if you are sat behind the band. If this is not possible then
get a friend to stand out the front to assist in balancing the sound.
Also try and have a listen when the room is full of people as a crowd
can easily absorb mid and high range sound.
Backline Levels
Back to Top
If you are only
running vocals over the PA system try setting the vocal level first
and then turn the guitar amps up to a nice level, don't try it the
other way round, you will probably run out of headroom for your vocals
and be running close to feedback all the time. If you have small
guitar combo's then you might want to elevate them off the floor,
otherwise your amp will be aimed at peoples legs and you could end up
with a very muddy sound, try putting them on a chair or flight case
(beware of flight cases with rattling handles!), don't set them so
high that they are spilling into vocal mic's though!
If you are having
every instrument mic'd up then don't have your backline amps running
at max level, let the PA system do the hard work not your guitar
combo! This will also help who ever is doing the mixing to control
the sound a lot better, it also helps to reduce the onstage sound
level which in turn will make monitoring easier to set up and cause
less problems with monitor feedback. Try setting the vocal level
first then bring up the other instruments to suite. Try and set your
vocal level so that you have at least 6-10 db of headroom before
feedback starts, that way if your engineer needs to turn up the vocals
during the performance he can do without causing feedback.
Mic'd up Drum Kits
Back to Top
If you are
planning to mic up the drum kit then you may want to consider the
following points:
PA output, if you
are running something like a powered mixer don't bother with the
drums, you will probably eat up all of the headroom very quickly and
end up with a poor sound.
Bass driver size,
don't expect to get a big concert sound off your kick drum if you are
running small or too few bass enclosures. We now use 21" Horn loaded
bass enclosures on all of our systems 4kW and above, this ensures a
big sound even in small venues.
If you are
putting a mic on the kick drum then you might want to consider the
sort of sound you want to achieve, if you are after the typical rock
sound kick drum with lots of low end punch and a nice snap then you
will need a hole in the front skin of the drum to position you mic
in. If you want a more natural sound then positioning the mic in
front of the skin is ok but this can give a slightly more muffled
sound.
You may also want
to think about using compressors and noise gates on drums, percussive instruments can
have a very large dynamic range, possibly greater than the PA system
they are connected to. If you are running the PA with little headroom
(as is usually the case with people running small PA's!) and a snare
drum is struck very hard it may well produce an additional 10db of
sound pressure, it is unlikely when running a small PA that you have
got ten times more power to spare as headroom, without compression the
results could be amplifier clipping and possible damage to speakers
not to mention the poor sound. Gating drums can also tighten up
the sound produced cutting out excessive ringing and unwanted
sounds. Typically for the kick drum a gate that closes quite
quickly should enable you to produce a tight punchy sound without
too much boom, as for snares and toms the gate may need to remain
open for a short period followed by a slow decay to achieve a
natural sound. Harsh gate settings can produce un-natural
sounds so be careful not to over do it!
If you are
placing overhead mic's on cymbals in small venues then you should
probably concentrate on the Hi-Hat and Ride, most crash cymbals can be
loud enough without any amplification and if all of the other mic's on
the kit are not gated then you will probably get some spill from the
cymbals anyway.
EQ Settings
Back to Top
When using EQ's
on instruments and vocals try and remove unwanted sounds first with
the EQ rather than boosting the sound you want, if you have to use
very heavy EQ settings to get the sound you need then there could be a
problem somewhere. The best way to achieve a good sound is to
position the mic in the right place first, don't try and use the EQ to
compensate for poor mic positioning.
If you have a graphic EQ on the
FOH mix try and set up the PA system with some well know music to get
a balanced sound in the room, if it doesn't sound too good then try
and remove any room resonances with the EQ if you have to use
excessive boost to get a good sound then this could point to a problem
somewhere, are all of the speakers connected properly and working?
When you are
setting up monitors it is often better to do this with the FOH
speakers off, also try and listen to the mix that you are giving to a
person rather than just tweaking knobs until they stick their thumbs
up, you will get a much better idea of what they are getting if you
can listen to it as you create their mix. Try and avoid sending very
low frequency signals to the monitors, normally you will only have a
12" wedge to work with so its hardly likely that it will be able to
produce thundering bass at high levels. If you have an Graphic EQ in the
monitor path with low and high frequency filters try setting the low
frequency filter to about 100Hz, this will probably give you more
headroom for the rest of the sound you need to hear. EQ's are
essential for good on stage monitoring as you can eliminate feed
back before a performance starts, try removing problem frequencies
with your EQ during sound checks by turning up the gain on the mixer
channel and listening for the onset of feedback and then notching it
out with your EQ, repeat this process until you are feedback free,
you should then be left with enough gain left in the system to carry
out your performance with no problems.
Getting your
mix right.
When it comes to
the final mix try and get a balanced sound where every instrument
can be clearly heard, make sure your vocals cut through the mix and
sound clear.
Don't run
the PA system at maximum level! Save some headroom so that there is
more of an difference between the quieter parts of songs and the
louder, you should then be able to make an impact during the loud
parts without distortion. Running the PA flat out all night will not
only sound poor but it may lead to premature speaker or amplifier
failure. We have often supplied pa systems and a
bands own 'engineer' has turned up, which is fine but all too often
volume seems to take priority over quality especially with young
inexperienced engineers, you then end up with a harsh sound and
incoherent vocals!
P.S. don't
forget the gaffer tape!
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