Sound Reinforcement for Dummies (and DJ’s) Hello Friends, And apprentice Audio Technicians, as well as hello to you, Thumb Drive Divas, and would be Artists of the DJ world. I have been in the business for more then 35 years, as an Audio Man, doing sound design, system engineering, and operator and head of sound for hundreds of events etc. But this is not about me ,this is about you.. This is the Brown Paper, of does and don’t ,for Dummies and DJ’s. Basic principals of sound reinforcement ,especially for the hearing impaired, high self esteemed, imposters that pose as Artists behind pre recorded low bit rate MP3 playing on Mickey Mouse technical gear. We will refer to these People in general, as DJ M ( M for Moron). I know most of those who should read this, will have already stop reading right now, because they think this is just bashing, or they have the attention span of a Gold Fish. Please ,try for once ,to read the fucking manual to the end, you might learn a thing or two. I was prompt to do this by a stupid DJ gig that I resigned from, because some of the people involved, were trying to make me do stupid things as far as sound reinforcement installation goes. I did not want my name associated with these idiots and their fly by night organisation. So. Chapter 1: Why is 4 Corners Sound Stupid, and has never and will never work. I have heard DJ M refer to this concept as surround sound. Having several speaker sources converging does NOT make it surround sound. Here is a basic text for your reading, and a quote from it: Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and presents a fixed or forward perspective of the sound field to the listener at this location. The technique enhances the perception of sound spatialization by exploiting sound localization; a listener's ability to identify the location or origin of a detected sound in direction and distance. Typically this is achieved by using multiple discrete audio channels routed to an array of loudspeakers.[1] https://en.wikipedia.org/wiki/Surround_sound So, for you the hard of hearing, it means that every sound source ,or array of speakers sources should have a distinct program playing, not, or possibly not duplicated in the other sources. Meaning you should have distinct playback channels for each of them. For a 4 corner set up, it is referred as Quadraphonic Sound. It is never the case for DJ M. I also Heard DJ M refer to this stupid 4 corner concept, with a stereo source, as creating a sweet spot on the whole surface of the dance floor. Let me demonstrate otherwise.

I am using Meyer Sound Mapp online, to post those figures. It is a well know tool for sound models and design in 2D.It works for any type of speakers. Remember: Sound propagation Obeys the laws of physics, and those laws are unchangeable. So,no,please don’t say that Funktion One crap will make it better, I will prove you wrong . Fig 1 to 4: Sub arrays in four corners. In the best possible installation for this non sense, all 4 corners arrays should be equal distances from one another.(this never happens.) Here is the results at 55 HTZ,as well as Virtual SIM microphone readings in different location of the dance floor, or watchacall it? The sweet spot?

Fig 5: You think this is a problem only for the subs?? Here is the result with the low-mids and highs speakers ON, minus the subs.

Center frequency is 80HTZ

And FR at Center converge dance floor,minus subs

Now, if you don’t understand those figures, try reading this first: https://en.wikipedia.org/wiki/Sound Now do you get it? In a 4 corner set up, the sound waves that are cross firing and facing each other, are creating cancellations, unwanted random additions and standing waves that are not manageable by EQ or any DSP devices. It is ,This concept of converging identical sound sources, what I call a comb Filtering Generator. https://en.wikipedia.org/wiki/Comb_filter It is what any Audio Man in the world tries to avoid at all costs. So, DJ M tells me that to avoid these low end propagation problems ( not his words, sorry..), some Installations would include subs in random positions in the room …well… They say it is not random ,but it is, because no calculations have been made ,and they put them where they have room to spare. And they are generally not of the same type, fabricant or model.. This is Wrong again. Remember: Sound propagation Obeys the laws of physics, and those laws are unchangeable.

If You Have to Over EQ a Recorded/Playback Source in the PA, it is basically that the basics of a good installation are not respected, that you have bad gear (FunktionOne),and you have not tuned the system using the proper DSP and Sound measurement tools. In these types of set-ups ,the DJ booth is also subject to the uncontrollable spills of low frequencies, making it very difficult to use vintage turntables and Vinyl because it is creating feedback. Fig 7: Low end result at DJ position.

Chapter 2: Audio gain structure, distortion, and SPL levels. The Question to DJ M is: Why?

Why do you want to hear your Booth Monitors louder then the back spill of a huge PA.

Why do you want it so loud in the room? Just take a walk there once in a while?? And my God,Why do you always end up sending distorted square waves into the

system from your so called Boutique specialized Mickey Mouse DJ consoles, or set up!.

First of all: Red Is Wrong!!!! Why is it so difficult to grasp!!! Read this,M, from one of your kind: http://www.djconquest.com/red-makes-amateur/

And this as well… http://www.parallelhomeaudio.net/TypesAudioDistortion.html

Now you end up sounding ,Mr.DJ M ,as crap, at any point in the evening because you think it is cool to overdrive the sound chain.. You Cannot help yourself, although we had a sound check at a proper level, without distortion. You are an idiot, and you will pay for the damaged gear. And if you don’t back it up when I tell you so, I will hit you with a Baseball Bat. Fig 7 :Bat

Now understand this: even thou the systems are protected, when you are sending DC square waves to be amplified, it will create damage to the components. And contrary as what those idiot DJ gear rental outfits think, if you have under power Amplifiers for the Speaker components being driven, it will not save you from it, but quite the opposite!!

SPL(Sound Pressure Level) is a measure of the sound pressure at any distance. The measurement unit is in DB.(decibel) There are several DB measurement scales. Here is a short definition from wiki, for the scales we normally use in sound reinforcement: dB(A), dB(B), and dB(C)

These symbols are often used to denote the use of different weighting filters, used to approximate the human ear's response to sound, although the measurement is still in dB (SPL). These measurements usually refer to noise and its effects on humans and animals, and they are widely used in industry while discussing noise control issues, regulations and environmental standards. Other variations that may be seen are dBA or dBA. According to ANSI standards,[44] the preferred usage is to write LA = x dB. Nevertheless, the units dBA and dB(A) are still commonly used as a shorthand for A-weighted measurements. Compare dBc, used in telecommunications.

Now, On his Princess Tech Rider ,DJ M writes that he will need a system that can reproduce sound at 115 Db. Tell me more?? At What distance? What scale do you use as reference? At what level of input should this system reproduce sound to this level? Need I say more? DJ M has also a very specific need for his listening Monitors, or Booth Monitors. What he asks for, is something that will impair your hearing permanently after prolong use, due to the type of speakers, the power and sound pressure of what these ensemble can reproduce, and the proximity of those to DJ M. Also ,being what he is and what he does, DJ M will play those monitors as loud as he can to impress his entourage, and thus creating another important sound source, that is not time aligned with the PA system unfortunately aiming at the audience. All of this adding to the confusion. And No, my DJ Friends, Playing everything louder then everything else does not make it better ,or cancel the echoes, or the comb filtering that your wanted installation has provided, and your demented use of it. Remember: Sound propagation Obeys the laws of physics, and those laws are unchangeable. Friends and I ( and a lot of pro Audio Techs) have come up with scientific, and model solutions for this type of events, even for a so called 4 corner type of sound propagation installation, and specially for low end/Subs coherent propagation and directivity...But it will cost you, double, to have access to this Data and designs...And will cost you a lot in Hi end professional gear and DSP. And even more to have me install and tune in on the spot. I got my ear plugs in ,so your noise and feedback will not be answered ,or read, or commented by me. Cheers!