In response to the Live Sound Considerations: Mics, PAs, Mixes and More article, a reader sent me a super interesting and informative email about using the EQ section of your mixer to “tune the room,” so I thought I’d share it with you…
How to EQ a PA System
GUEST POST BY LONNIE SHURTLEFF
I will venture to add some detail to the discussion of the EQ process, the first point being to understand what the EQ section is and what it does, and consequently, how to take advantage of it.
What Happens When We Sing (or Play) Into a Mic
When a sound strikes a microphone (of whatever type) it generates an electrical signal that (theoretically at least) duplicates the characteristics of the sound.
(We’re talking pitch, amplitude, harmonics, phase, etc. – technical stuff here).
It never works 100% perfectly – that’s why different mics sound differently, and why a sound technician will choose different mics for different applications.
That electrical signal typically travels through some cabling to a channel preamp. From there, that signal (along with others) goes to a power amplifier, which in turn strengthens the signal and ships it out to some transducers (speakers) via cables again.
The speaker’s job is to bounce air molecules around in exactly the same way that they entered the mic but many times BIGGER and LOUDER.
The amplifiers are never 100% perfect. Neither are the speakers. The cables always have issues and affect the signal somewhat.
There is a lot of technical stuff to learn here if you want to be an engineer, but for our purposes, these are things that affect the signal.
These things are part of what the EQ section is supposed to correct.
The PA’s All Set Up – Now What?
Suppose you set your PA up somewhere quiet, outdoors, maybe in the desert, with nothing close by to reflect or otherwise mess with the noise. Everything is set up flat on your mixer.
Crank the master gain up, and what comes out of the speakers is (supposedly) what the sound going into the mic was, only BIG.
(It’s not really the same, but the only way you could sort it out would be by making measurements with expensive audio test gear.)
So, all you have is your ears, and you think it sounds “muddy,” or “shrill,” or “thin,” or “distorted,” etc.
So you “smiley-face” the EQ (boosting low and high end, and dropping some midrange frequencies) and use it like a tone control–and it works!
It sounds much better!
It works largely because the human ear does not work in a linear fashion and it hears soft sounds differently than loud ones.
But this is not really what the EQ section is for!
Most of the time, you are not out in the desert. You’re inside some structure or room that has walls and ceilings and floors and windows and reflective surfaces.
Some of the stuff in the room absorbs some sounds and some reflects some sounds.
Here’s where that EQ section really earns its keep. You set up your gear, and then…you EQ the room! You make that room behave like it was the middle of the wide open desert.
Here’s how I like to do it…
How to EQ The Room
After everything is set up, using only one mic with the channel gain about 3/4 up (that is usually a pretty sweet spot for the preamp), other mics off, monitors off (we are EQing the mains and the room–monitors are a separate deal!), then…
- Put the EQ sliders all about half way up
- Start bringing the master gains up (CAREFULLY!) until something starts to squeal or roar or whistle (feedback).
- Hunt around on the EQ bands and find the slider that affects that sound the most, and back it down a bit.
- Next, push the masters a little higher until you get feedback again in a different place. When we get to the point where we have touched most of the sliders, and any more gain brings random feedback at different pitches, we know we are compensating for all the different stuff that’s reflecting and absorbing sound in that environment. That threshold is the maximum overall amplification that can be applied in that environment. (A more sensitive mic or an omni-directional mic will cause that threshold to be lower, which is why we typically choose cardioid mics like Shure 57s and Shure 58s.)
- Then, simply pull the masters back away from that feedback threshold and the room is EQed!
- A simple trick to spot check this is to cup your hand around the mic. If it starts squealing, you’re too close to that feedback threshold.
Now, bring the other mics up and use the channel controls to make each mic sound good.
That’s what those controls are for!
This leads to a couple of final thoughts…
You probably just EQed a cold room! When the sun goes down, the temperature drops, the humidity goes up, people fill the place up with smoke and sweat, etc., the EQ changes, and you’re going to need to tweak it on the fly.
But at least you know you started in the right place!
Typically, hot humid air soaks up highs, so a little boost in the top end will help.
Also, the human voice likes a “presence peak” around maybe 2kHz or a little higher.
Rolling off some bass down around 400 Hz will often clean up “muddiness” and “rumble” in the bottom end.
Lots more to share, but I’ve already written a book here!
Editor’s Note (from Dave)
I asked Lonnie if there were other practical tips he’d want to share concerning live sound, and here’s what he said:
“There are a bunch of other aspects that I might talk about, for instance…
- how to get that little “ball of sound” around your head that makes it possible for you to perform at your best
- why people grouse that “It’s too loud!” when that isn’t really the problem at all
- why everybody else sounds out of tune when it is really the bass guitar
- (if anybody really cares) what Dbs (decibels) mean and why it matters
- stuff like “low impedance vs. high impedance,” “balanced vs. unbalanced mic cables,” “4 ohm speakers vs. 8 ohms” (rabbit hole stuff)
- or maybe how to set up the pickups on your Strat (kinda problematic)
- or why Leo Fender designed a flat peg head that required those little string-hold-down thingies that make a Strat so tough to tune!
Looks like I’m on a roll again, sorry!”
Lonnie said he’ll be glad to respond to any questions or comments this might provoke, so jump into the “Comments” section below and let’s discuss!
About The Author
Lonnie Shurtleff, aka “Lonnie The Eclectic Cowboy,” is a retired broadcast engineer terminally addicted to guitars and getting people to laugh and clap.
Based in La Grande OR, Lonnie performs wherever he can afford to go. He’s in the Artist-in-Residence program from Arts East serving ten rural counties in Oregon, performs in two duos doing everything from big band swing to Oregon Trail “Americana,” and does cowboy poetry workshops in schools and libraries where he talks about the history and legacy of the west.
About The Blog
The Educate and Entertain blog provides articles, tips, encouragements, and how-to’s for regional performers (in any region) interested in making a great full-time living in the arts.
Good article Lonnie, I was looking for a way to show my brothers band how to eq properly (apart from my view). Your description is great, but I wonder. I was taught by an engineer in Australia who mixes the big international acts and he told me exactly what you have said, but to stop at three peaks. The eq should be flat with only the first 3 peaks pulled down. They are found exactly as you described. Reason is – your job is not to colour the sound, just to make it louder. 3 peaks on the equaliser are enough to flatten the pa without adding colour. The parametric or eq on the desk is then used for each individual instrument, and compression/limiting finishes the deal Just interested to see what you think of this. Great article mate. Regards Todd.
I havent seen anything written so far on headset mics w/ radio frequency channels and Bluetooth mics. I use a Samson headset mic with its transmitter plugged into the PA channel of Fishman Loudbox battery amp. My electric harp plugged into other channel, Im planning to test out my new repertoire outside as well as inside. I do not have an EQ. Just use amp controls. Any advice?
Thank you Lonnie!
One thing I’ve wondered, I usually use quarter inch jack cables for instruments and 3-prong cables for vocal mics. I have some mic cables with a quarter inch jack on the end you put into the mixer, does it matter if i use that vs the cable that has 3-prong (“balanced,” i think it’s called) type on both ends?
I yearly work at the local arena
(5000 people). System is very trebally. Is there something I can do with my mic to make it with more bass. I do NOT have access to the arena’s sound board. Thank you
Thank you, Dave for reposting this old material. John’s old post regarding the arena system sounding very trebly caught my attention. Great question! The short answer is, “Almost certainly not!”
Remembering that the arena system was designed for maximum intelligibility of the human voice at high volume in a large “soundscape”, probably does not even have the capability of sounding big and warm for singing and music. Think about singing over an old fashioned telephone–not optimized for music transmission. I might be wrong here. If they can play recorded music through the system and it can recreate the huge base sounds of some modern genres, then perhaps it does have the capability…but you don’t have access to the mixer for your individual channel anyway.
What you can do, however, to make your performance easier is to make the “ball of sound” around you head more conducive to your artistic expression. Still tough, but this can work. find a way to obtain your pre-fader mic signal (you’ll need a splitter) and route it into your own EQ box (probably a battery powered unit that you can locate somewhere close to you or hang on your belt) and feed a set of ear buds with that signal (will need some amplification…headphone amp, 9volt battery, I’ve built a few in years past for radio work…).
Or another idea pops into my head, a little mixer board, Behringer 4 channel, etc. that has those capabilities, probably with digital effects and a bunch of other stuff that will make you sound great in your own ears.
Bottom line, if the arena system has the capability of big warm bottom-end sounds you can find a way to (perhaps radically) EQ your signal before it hits their board. If their system cannot sound big and warm, you can split your signal to your own miniature system to obtain a better working environment around your own ears. Great question! Lonnie
A final consideration would be to try and choose material that will come through their system reasonably well.
Great as always to have you returning to chime in here, Lonnie!
I LOVE this! I hate to admit how long I’ve been talking/singing in front of live audiences without knowing this stuff. Can’t wait to try it out at my next gig. Oh – and, I’m probably the only one but, I’ve always wondered about that whole ‘High impedance – Low impedance’ thing. I’ll grill the brats and buy the beer if you’d like to take a shot at explaining it to this troglodyte. 😉
I’ll venture forth! lol
As a woodworker, I think I know why Fender guitars have the “flat” heads. Because it’s easy to make, involving less wood and joinery. Personally (again as a woodworker) I have never found them to be attractive. Give me a Les Paul head any day!
As for setting up a PA? I can’t imagine having the luxury of taking my time and making feedback noises. In the world of club and restaurant gigging, there are always people there and the less annoying I can be, the better. Plus, as you said the dynamics of the room are going to change when more people show up. Sadly, If I can hear myself, it doesn’t sound too horrible? Good enough for now, maybe a little tweaking as I go. One thing I love about my Fishman tower is (unlike the old monitor days) what I’m hearing is what they are getting. The only tricky part is getting the volume set for them and not me. Which in my case (standing in front and to the side) means setting it just a bit strong, which is actually wonderful as I can hear my voice and guitar very well. When I’ve used other people’s set ups, I often have trouble hearing my guitar, which results in playing harder, which in turn results in them turning me down more. But when I’m in front of my own PA, I play my best!
Charles, you have hit the nail on the head! (Bad pun, I know). I believe Leo’s decision to make the head stock flat was so that he could get the entire neck out of a single piece of 5/4″ maple. Then, since the break angle over the bridge is not adequate, he had to go to the little twiggy string hold down things…which introduce numerous issues. Just tonight a friend and I were discussing the idea of taking a fender-type neck and making an angle splice right behind the nut to angle the head stock back about fifteen degrees. Haven’t tried it yet.
Regarding your PA set up comments…yeah, its sometimes pretty difficult! The “people considerations” necessarily drive a lot of the compromises we accept. My own experience with the Bose LP-1 was not very positive, but the unit did perform its auto EQ silently and effectively. I’ve spent too much of my life in the situations you describe. Many times I have come in at a slow time of day like early afternoon and done my best to set sound for our group. If you are careful, you can search for those feedback points without the folks at the bar ever noticing. Can’t do it when the juke box is going, etc. I’ve also waited until the barmaid was stacking chairs on tables and mopping the floor to EQ the room so that I had a starting point. With some experience you can walk into a room and look at the double glass windows facing the street or the brick wall behind the bandstand or the draperies in the alcove, etc and have a pretty good idea of what you will need to do.
When you talk about the volume settings, and the sound guy turning you down and your response by just playing harder, you are describing exactly the difficulties referred to when I talk about obtaining that sweet little “ball of sound” around your head so that you can perform at your best. To me that is the most critical part of the whole thing! I’ve never performed with ear phones or ear buds except in a studio setting, but I think that is one approach worth investigating. The discussion concerning monitors and side-wash systems, etc. becomes long and complicated and above my pay grade.
thank you fro reading my little article. Hope you were able to take something away from it. Lonnie
Hey, guys – Fender fan here. Just read today about a player who bought staggered height tuning pegs so he could get rid of the string trees (yeah, that’s what they’re called). This is new to me but may be worth looking into if you love your axe but hate dealing with the tuning issues. Chill – Jim
Thanks for the nice article Lonnie. What is your view on Feedback eliminator type units?
Rob, I replied in the wrong place. Scan on down to my response below MattW’s Frequency Analyzer question for my comments. Sorry! Lonnie
Kinda got your question tangled up with his. I am not really sure what devices you are referring to. The clipping alarm circuitry in many PA heads shows you what freqs are being hit the hardest and may cue you as to what might need to be done to flatten out the power amp, but that is not really eliminating feedback In the room. Bose and Fischman and others have intelligent circuitry that EQs the room for you and they seem to do it quite well. My experience with them is limited. Sorry I cannot be more specific in my response. Lonnie
Does anyone use smart phone frequency analyzer apps for tuning a room?
Sorry to be so long replying to you. I’ve been out of the country.
I’m not aware of any of the local guys using that technology. I’d be interested in learning more about it, for sure. One pragmatic issue that I see is, (as with using most test gear) what do you do with the information it provides?
A freq analyzer will tell you the response/reflectivity of various sound frequencies in the room. An advantage of the cell phone is that you can walk around the room and watch the responses change. The old fashioned way of doing that is to walk around and clap your hands and listen to the reverberation coming off the walls ceilings, glass windows etc.
What you are really concerned with, is how it is all working at the microphone location–and what to do to adjust for the inevitable reflections and adsorptions in the environment. A freq analyzer may be overkill for this situation, more info than you can make use of. Pretty interesting though because ti allows you to get a real feel for the effects of various sound-modifying aspects of the room, like draperies, diffusion shapes, angled reflecting surfaces–stuff you deal with when designing a radio or recording studio. Thanks for the comment.
An interesting question! I personally am not aware of anyone using them but I am not in the full-time touring and gigging community anymore. I have looked at some broadcast studio installations with an audio frequency analyzer, but that is old history now. The technology has advanced very rapidly in the last decade or two. I have come to trust my ears and experience mostly.
I expect the learning curve would be to understand the data on the phone well enough to make decisions concerning things like room resonances and optimum speaker placement and such, and then figure out a way to work around them, because someone decided to put the bandstand in the corner (typically a terrible place) or some other audio mine field situation. Thank you for your comment. Lonnie
Hi Lonnie – great article, thank you very much. I have a couple questions about the process…
Where do you place the initial microphone used to EQ the room? Is there a sweet spot for that?
Also is there any signal going through the mic while EQ’ing (ie. singer saying “testing 1,2”, “testing, 123”)?
I suspect this process is slightly different if using a Bose, Fishman, or JBL stick-style PA’s since the mic is typically in front of these and used for both PA and monitor – would you agree?
Thanks again – much appreciated!
ps. Would love to read more about the “ball of sound” and the “too loud” issues you mention!! 🙂
My apologies for the delay in responding, I’ve been out of the country for a couple of weeks
Think about where you want the audience to focus their attention–typically center stage. that’s the mic I will choose to EQ the room. .
Yes, there is actually a signal going into the mic. What you want the mic to hear is the pure ambiance of the room–pretty low level. That’s why you will have to drive the gain way up to get the feedback that will identify the sonic structure of the room. Best not to have a bunch of music or other significant sound going on like singing or playing or a stereo blasting away.
The big deal about the Bose and the other “intelligent” systems is that they do this for you automatically when they first come on. Pretty neat–and you don’t even hear it! And of course, it is that active “intelligent” circuitry that allows you to stand right in front of them without the squeals and roars that you would expect. Be a little careful with your Bose gear. I have had a bad experience with their version of customer support.
The short version on “ball of sound” idea is that by use of monitors and stage EQ and etc. you strive to make that “ball of sound” around each performers head sound just the way he/she needs it to sound so that they can really get into what they are doing. It is as much about understanding how they work as it is about knowledgeable application of the tools you have available. I’ll write more if Dave thinks it might be useful.
Regarding, “Too loud…”, it is usually a perception issue (often related to EQ and harmonic distortion) more than a question of volume. If your sound is very “clean” and you system has excellent “projection” you can actually operate at high volume levels without being perceived as “Loud”.
Are you familiar with the difficulty of hearing across a set of drums when they are in the middle of the band? some of the same issues are involved, masking frequencies, hearing algorithms, etc. Pretty interesting! Thanks very much for the comment1
Ol’ Leo, the Henry Ford of the electric guitar, was concerned with ease of manufacture hence the flat headstock and string guides. The vintage-style round ones on a Telecaster are cool. So why DO people grouse that it’s too loud when it’s not?
Lol, Yeah, good ol’ Leo! Basically, it comes down to distortion (read “added harmonic content”–the very thing that a guitar amplifier must do to make a thin-sounding plank instrument sound interesting). Play your typical Strat through a good PA system–not very compelling.
When people cannot carry on a conversation through it, it is perceived as loud. Lots to think about here. thanks for the question. Also, see the above comment concerning drums for additional insight. Thank you for the comment.
This was incredible helpful, especially for newbie like me. Thank you a ton!
Your comment just made this old cowboy’s day! You’re sure welcome!
You’re sure welcome! Thanks for the comment!