Common DJ Sound System Mistakes

in on Jun 27, 2012 . 1 Comments.

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!

Tags: dj tips, mistakes, sound system, audio tipsLast update: Jun 27, 2012


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