I’m a DJ, what’s this got to do with me?: We are looking at the difference between the home/studio environment and the problems caused by the increase in volume in the live environment. Microphones for vocalists are prone to feedback, usually caused by the vocalist asking for an increase in volume from their monitor speakers, which does not usually happen in the home studio.
There is also another set of performers who will encounter problems when transitioning from the home studio to the live environment––turntablists and DJs. The rise in popularity of software such as Ableton LIVE and Cycling 74’s MAX have created a new breed of musician who primarily use laptops, turntables and interfaces in the live environment. DJs and turntablists are also common parts of any modern concert, either as part of the band or by supplying warm-up/support music.
Unfortunately, turntablists often have problems with feedback. This feedback is caused by the bass frequencies of the music (obviously vital if you are trying to get people to dance) being picked up by the needle cartridge of the turntables and being amplified back into the PA system or monitors, just as in the vocal feedback loop. This feedback is not solely limited to vinyl record direct-drive turntables such as the legendary Technics Sl-1200 decks; CDJ decks, vinyl replication systems such as the ones based on Serato Scratch and laptops can be adversely affected by feedback, causing the audio output to jump or stutter. Feedback caused by vinyl turntables is usually in the 80 to 110 Hz frequency range but bass frequencies in that region, whether from feedback or just being too loud in the club system, will upset also CDJ decks and laptops.
Most DJs or turntablists will panic and turn down their own output levels if a feedback or jumping situation occurs and that kind of ruins the vibe––suddenly the music for the audience has been turned down which is not a good way to keep a party going. Luckily, as with the vocal feedback loop situation, there are ways to avoid the problem in the first place.
You should avoid excessive EQ and gain on any DJ mixer or controller in order to prevent exaggeration of the bass frequencies. Do not crank the bass controls on your mixer and also set your input gains so they are not showing red on your meters. Have all the tone controls set flat—in other words, not boosted and not cut (until you are creating bass cuts for effect). Remember, less is more. Ask the house/club sound engineer to cut out the most common problem frequencies, such as 100 Hz, in your monitor system. Place the monitor speaker on a case or stand so it is closer to your ears (that way you will not need to have it so loud as it is nearer to you), and then make sure the monitor speaker is not touching any part of the DJ table or stand. The bass frequencies from the speaker may be transmitted through the DJ table or stand if it is, adding to the chance of bass feedback.
You then need to make sure the turntables/laptop system is as isolated from general bass frequencies as possible. I have seen a variety of methods of isolation—foam under the turntables, tennis or squash balls cut in half under turntables/CDJ decks, and even suspended turntables. I personally always use two paving slabs under each turntable or CDJ deck. It is a major pain to tour with a bunch of paving slabs as they weigh a lot, but I very rarely get bass feedback from my touring turntablists when I use this method.
What’s that sound?: Beyond combatting feedback, you may also encounter other sound issues when performing live. It will help you if you know how to talk about these sound problems in the correct way.
Sounds that you hear as musical tones are made up of regular, evenly spaced waves of air molecules. The distance from the high point of one wave to the next wave’s high point is called the wavelength. The frequency of waves (or cycles) is measured in Hertz (Hz) which is a measure of how many cycles (wave peaks) go by in one second. Therefore, a 1-kHz tone means a wave with 1,000 wave peaks per second. The average human can hear sounds that range from about 20 to about 17,000 Hz.
It is all well and good knowing about frequencies, but in the real world of your musical career you do not ask your piano player to give you a tone at 440 Hz as a reference when checking the tuning of your instrument. Instead, you would probably ask her to play A above middle C (which is actually 440 Hz in “concert tuning”). You musicians know the sound frequency as pitch and that’s the way you communicate how you are hearing sound—the pitch of a vocal or instrumental note. That is your “language.”
Playing music onstage will bring you into contact with engineers and technicians who have another language—they understand frequencies and will communicate about sound issues in that language. They might say to each other, “It’s a bit peaky at 5kHz,” when describing the sound coming from a monitor speaker for instance. Luckily for you, many house engineers and touring audio professionals are musicians as well, and so they can speak both “languages.” It therefore makes sense that you do, too. Suppose you are standing onstage and listening to the sound coming from your monitors. The sound is wrong to you. You say to the monitor engineer, “This monitor sounds wrong.” How is she supposed to know what you mean? Do you mean the mix of instruments is wrong? Is the monitor too loud for you? Too quiet? Is the sound distorted? Conveying your thoughts in a language that everyone understands will really help you to get results.
Instead of saying, “This monitor sounds wrong,” suppose you actually listen to the wedge and decide you can hear an odd sound in the monitor, which is making the sound seem dull. You would then perhaps say to the engineer, “Hey, there is a low-pitched rumbling sound in this monitor.” The engineer might say, “Okay, how low?” You might not be able to pinpoint the exact frequency but at least you have given her a definition of a problem. You could perhaps try to replicate the pitch on your instrument––that would then give the audio engineer a guideline as to the problem frequency, which will ultimately help both of you.
