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Common
DJ Sound System Mistakes by
Mike Starnes
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What not to do if you want your sound
system to sound good and last long
1. Mismatched power - One of the most common mistakes made with
mixer-amplifier-speaker combinations is the use of components that are not
evenly matched. For example, say you have a pair of speakers rated at 300
watts continuous power and 600 watts peak. This gives you an operating
range in which to place the amplifier that you’ll use. Check to see
whether the speakers are eight ohms or four ohms in impedance. The next
step is to check the power rating on the chosen amplifier at that specific
impedance or ''load.'' It is very easy to do speaker damage by using an
amplifier with insufficient power. The lack of “headroom” or reserve
power may cause the smaller amp to clip, sending a distorted signal to the
speaker, resulting in blown woofers or tweeters.
2. Improper speaker placement - There are no absolutes in speaker
placement because of the variations among rooms at different locations.
The basics are only a starting point.
Imagine your system set up to play. The speakers are to the left and right
of your centrally located console. Theoretically they are facing away from
you toward the crowd. You want the best starting point for optimum
performance, lateral projection, vertical projection, and feedback
elimination. Thinking right angles (remembering again that there are no
absolutes), draw an imaginary line from the center of the speaker at stage
left to the speaker at stage right. Your DJ microphone should be at a
ninety-degree angle to that line, facing directly toward you to achieve
maximum announcement volume. The horns in each speaker may have lateral
dispersion patterns as wide as 90 to 120 degrees and vertical dispersion
from 40 to 90 degrees. Imagine yourself standing on top of the speaker
with your thumb on a water hose (please don't try this at home). If the
pattern of the water matches the projection pattern of the horn, then
everywhere the water goes the consonants you speak also go. The higher
frequencies that are more susceptible to feedback are present in the
patterns of the horns. If the speakers are slightly farther back or angled
inward, the pickup pattern of your microphone may overlap the projection
pattern of the horn.
Another simple hint is to stand mount the speaker to counteract the fact
that most of the audible speech goes into the navels of your audience
rather than into their ears. Yes, if the speaker is elevated you may lose
the ''coupling effect'' that adds bass from the floor. Of course
subwoofers are a better alternative than the floorboards. There's also a
small pointed area between the speakers, directly in front of you, called
''The Dead Zone.'' There are limited highs there as well. Ya’ win some,
and ya' lose some!
3. Improper wiring - The gauge of the wire used to move the music
from amplifier to speaker is also critical. Remembering that smaller
numbers indicate larger gauge in wire, we recommend that for short runs of
50 feet or less you use at least 16-gauge speaker wire. 14-gauge is
preferred, but you can get away with 16 in this application. Since the
wire itself has ''resistance,'' a good rule to follow is larger wire (with
smaller numerical gauge) for longer distances. You may be using 16-gauge
cable at the present time for speaker runs of one hundred feet, but you
also may be sacrificing some of the performance. You may also be forcing
your amplifier to work slightly harder to get the same level. The same
rules apply to your electrical cables. Did you ever wonder why they get
warm? They are screaming for more copper, and a thicker gauge. The expense
is slightly more, but your gear will last longer.
4. Insufficient coverage - This occurs when you have 1,500
screaming teenagers in a gymnasium, two speakers on the floor, and a
300-watt amplifier. Parting the hair of the first eight rows of dancers
with high volume music in order to make it audible for those in the rear
of the room is no longer acceptable. Renting, purchasing, or borrowing two
more speakers with stands may be the difference between one gig and a
string of repeats. Advance the booking, research the numbers, add extra
gear if needed, and save your speakers from damage. Most amplifiers on
today's market will easily handle four 8-ohm speakers. Please note that
their power also increases to all four cabinets!
5. Imbalanced gain structures - Please note that with the massive
strides in technology in the last few years that the operation of most
sound systems has become more ''forgiving.'' If an older system were set
with the gain on the power amplifier low and the master volume on the
mixer at a high position the sound would be audibly distorted. The newer
amps and speakers do not exhibit the same tendencies, but it is usually
(the key word here is usually) better to run the levels on the power
amplifiers higher. Those of you who still run your DJ mixers into a
PA-style amplified mixer (and you know who you are) please remember that
your systems are more prone to preamplifier distortion through pilot
error, since you actually have two preamplifiers. Run the master on the
amplified mixer high and control the gain with the DJ mixer. As a general
rule, the best performance of Crown, QSC, Peavey, American Audio, and most
of the other current amplifiers is best utilized at the higher settings on
the amplifier, with the mixer to ''control'' the level.
6. Improper amplifier ventilation - Almost all of the current
amplifiers have two-speed fans that preserve the sonic integrity of their
internal workings. The switching amplifiers that boast low weights do so
without the use of larger heat-producing transformers so they are more
susceptible to voltage variations than heat. These internal fans usually
pull air from the rear and force it out the front (or vice-versa). The
fans assist in the dissipation of the heat generated within through the
use of external cool air. If the catering director skirts the console
table, sealing all four sides of the amp rack underneath, then warm air is
re-circulated. Simply raise the side facing you with pins or clips so that
some cool air gets in.
Will your amp shut off when it gets hot? Probably not, since the
protective devices in most of the newer amps are electronic rather than
thermal, but it will last longer and work better if it is kept cool. By
the same token, vent panels and open spaces between amplifiers help.
7. Improper equalizer use - An increase of three decibels on your
equalizer can translate to double the power to horns or tweeters in your
speakers. Excessive exposure to high frequencies can also induce
''listener’s fatigue'' and cause your dance floor to look like an Enron
stockholders meeting. Less is more. Start with the ''flat,'' or
straight-line theory, and use the EQ sparingly. If you ''have to'' use the
EQ a lot, it may mean that your speaker system doesn't sound like it
should in the first place.
8. Poor microphone technique - This is usually exhibited when your
mic falls into the hands of the best man at the wedding or the class
representative at the reunion. Most microphones designed for speech
exhibit what is called a ''proximity effect.'' This means that in close
proximity to the person speaking they have a full, bass-heavy sound.
People speaking slightly off axis or farther back tend to get a sound that
is thin and more midrange heavy. In a baritone voice sing an ''ooooh''
sound while turning the mic from side to side and moving it slightly away
from your lips to see this effect. Two hints would be to get a washable
windscreen for your ''Other guy microphone'' and to instruct non-DJs to
''eat the mic.''
9. Ill-maintained gear - In other articles we have stressed the
importance of preventive maintenance. Here we go again! On an off day
remove grills on your speakers. Gently clean or repaint the face of the
cabinet. This can be done with a careful vacuuming or with a paintbrush
used for dusting. Remove the input panel to tighten all jacks and
connectors. Touch up all solder connections. If there are rattles,
diagnose and fix them. After cleaning and drying the small paintbrush, use
it to dust off the face of the mixer. Be careful of switches and knobs.
Check to make sure all grounding posts are intact. Using a two-prong cable
may result in damage to you or your gear.
10. Pilot error - Think about what you are doing. Remember your
turn-on sequences. Don't turn off the mixer/console with the amp on.
(Pow!) If you see someone banging the palm of his hand on the ball of your
microphone immediately drop the master volume. (Wait until after the event
to Riverdance on his chest.) Such tapping can actually cause a blown
woofer. Watch your bass settings, and check your overall volumes. Route
your cables out of ''harm’s way.''
See your dentist twice a year and let us know if anything we publish
changes your life…Happy Trails!
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