# EQ Techniques-Suggestions



## stjc15 (Nov 19, 2006)

In my years of experience in sound, I have learned that it is important to eq your system. The problem is, I have never learned a good way to eq a system. How does everybody else eq their system? Which technique is the best?


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## Footer (Nov 19, 2006)

Depends what I have around. I rather like the way the peavey CEQ eq's a system on an RTA. If I am doing strickly voice I EQ to someone standing onstage talking into a mic. Otherwise a piece of music that has good vocal quality as well as decent music quality. I try to choose music that resembles what the PA will actually be used for. For most events I usually do a bit of Rent, a bit of Wicked, and a bit of Sting. If i have a 31 band I drop all the frequinces to as low as the will go and slowly add stuff in.


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## soundman1024 (Nov 19, 2006)

I would say there are two ways to EQ a system. You can EQ it for best audio quality and most gain before feedback. EQing for quality is certainly the more difficult of the two. Perhaps the easiest way is to use a flat response microphone and some Real Time Analysis software with white noise to get the system as close to flat as possible. The goal here is to account for imperfections everywhere down the line, and it is only as reliable as the microphone, the preamp the microphone for RTA goes through, and the purity of the white noise (the output device may have aberrations in its output). EQing for Gain before Feedback is EQing to take out frequencies where a feedback is more likely to occur allowing for more gain. Here quality is something that is desirable, but it takes second place to volume.


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## SHARYNF (Nov 20, 2006)

This is one of those seemingly simple questions that could turn into a very very long thread.

First a slightly different perspective than the two earlier posts.

There are two different uses of eq, one is for monitors, were you are to get the most GBF (gain before feedback). Here an rta hardware of software helps, very experienced folks learn to be able to detect the frequency by ear and make the slight adjustment. The RTA helps to identify the frequency. All the work here should be done with the mic being used on stage, NOT a rta dedicated mic and you need to check for mic positioning, cupping your hand around the mic etc, all those actions that the mic user is likely to use. Typically this is called ringing out the system. You can have several options of how to do this

There are automatic systems, like Sabine Behringer etc, which detect the offending frequency and have a very narrow filter that they use. In a pinch these work, but you loose control, and you can very well wind up with a sound in the monitoring system that has good GBF, BUT poor audio quality.
You can use a parametric eq or a 1/3 octave graphic. Graphics are typical, but you need to realize that the marked band is the center of the frequency area being affected, that there is quite a bit of overlap and the tool is not as fine as you might suspect. A 1/3 octave does NOT mean that only a 1/3 octave is affected, but rather that the center point is at a third octave point, Subtle but major point. A parametric gives you more precise control, and with a rta can be quite effective. Most of the auto systems use parametric technicques, and they argue for their effectiveness based on this. 

IMO it is NOT a good idea to simply drop all the 1/3 octave faders and then boost. First, as I mentioned each fader has quite a bit of influence on the adjacent frequencies, and for feedback elimination you should be reducing frequencies, not boosting the ones around them. Sometimes this idea comes from the technique that IMO you rarely ever want to boost a frequency about the zero line, but simply reduce the frequencies, SO in an extreme this could be interpreted as supporting the bring all the faders down to the minimal setting.


House eq is a different matter. Unfortunately a lot of people thing you just get a good ref mic, set the mic up and use the analysis to "level out" the room. The joke is the way to level out a room is with a bulldozer ;-)

Problem with the set the rta mic up is that you are doing it in a room where the reflections from the floor etc will have a dramatic effect on performance, and you typically have really extreme effects. In most cases these days people now look at really not using Rta systems to alter the room, but rather too correct the speaker system for its non linearities.

SO you are looking for smooth transitions at the crossover points, you are looking at time alignment combing etc. Problem is that these are usually a combination of some graphic but typically a DSP system like Driverack or BSS . IN addition a lot of the settings should have been properly set during installetc.

So graphic eq on FOH is something to be approached carefully, listening to music you know is very helpful, moving around in the room etc. making small changes and then going back and checking from the previous location etc.

An experienced person typically when the see a graphic set up on mains that has dramatic all over the lot adjustments knows that it has been done incorrectly mainly based on a simple rta mic with an auto or semi auto set up.

The other thing to realize is that the frequency performance in a audience space is related to humidity and temperature, and also absorption. I know people selling auditorium seats talk about same absorption characteristics as people but that is just a minor part of all of it.

So imo look at eq on the main system as correcting the speaker system NOT THE ROOM. There are some cases where you have a horrible room with massive reflections, or an apparent standing wave problem. IN most cases you are better correcting these with physical techniques if at all possible rarely will the graphic fix this.

One technique is to set the graphic for foh flat, and play some music that you are familiar with, and then go thru and carefully boost the various frequence bands one at a time, and hear the increase of NEGATIVE effect, and then use
the eq to reduce these areas.

Another reason not to use the boost is that here again is where you can cause distortion or over driving in the system with expensive results (blowing the driver/speaker). For instance you have a multi way system, with a cross over system if you boost the signal around the crossover point you could overide effectively the cross over frequency and for instance put too low a frequence into a high freq driver, remember crossovers typically have 12-18 db roll offs, and you could off set this easily with the graphic.

There are some cases when you need to look at feedback elimination on main speakers, but if the system was installed properly this should be less of an issue as the speakers should not be placed so that the output feeds into the mics. Improper install or placement can lead to problems, most of the time you should first try to move the speaker or the mic.


The other eq is for the individual signals to get the correct tonal balance you want based on the mic performer etc etc. That is where you tend to do more individual tweaking.

So in general, monitors get rung out for feed back elimination\
Mains get eq'ed to smooth out the response of the speaker system
mics get eq'ed for tonal support 

Just some ideas

Sharyn


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## soundman1024 (Nov 20, 2006)

Often it is good to avoid a feedback destroyer as Sharyn advised. I'm of the thought process that a well set up system does not need them. And also like I said, using RTA software and a flat mic is probably the easiest way to EQ for quality. Doing it by ear is something I'm not experienced enough to do.

In addition defining a few words might help. When I found out what these all meant it helped a lot. An octave is double the frequency. One octave would be like from 1kHz to 2kHz, or from 50Hz to 100Hz. In addition the ear hears the difference from octave to octave to be the same, so from 100 to 200Hz sounds like the same gap as from 1kHz to 2kHz. So a 1/3rd octave EQ will have 3 sliders per octave. The "Q" function on a parametric EQ will change how wide the area affected by an adjustment is, from fractions of an octave, to octaves. Also an octave in music is the same, so from C to C (C2 to C3 for example) is doubling the frequency.
You might see "cents" used with octaves. They are simply one 1200th of an octave. Very small measurement, not really dealt with in audio for the most part, but good to know of.
Also a parametric EQ is an EQ with 3 adjustments per band, one changes the frequency of the center, one changes the width of the frequencies changes, and one changes the amount of gain added or reduced.


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## BNBSound (Nov 23, 2006)

I've used any and all of the above, but here's the short format of my two cents. In any situation you can simply throw on a CD, and listen on a good pair of cans, adjusting the FOH graphs until the room sounds as close to the cans as you can get it. That works best for situations where playback is the main concern. 

For vocal reproduction, you've got to address the feedback situation before tailoring the room to suit the program. When an RTA is lacking, you just have to make the room ring and try sliders on the graph until you find the right one. When an RTA is available, don't rely on it too much just as you shouldn't rely on an automatic feedback eliminator. Any monkey can look at the RTA and level the room out, that doesn't mean things will sound good after he's done. 

I have an RTA in my rig, it's actually a retired DEQ2496 digital EQ that I used to use FOH. I usually don't plug in the calibrated mic anymore. I just rest it on the dog house of my console and plug the wedge output into the left input. That way, what ever is solo-ed reads on the RTA display. It's higly useful for finding what frequencies to notch in a hurry, and the more I use it the less I need it, my ears are becoming more and more trained. But even when I can pick up on what's wrong with FOH by ear and tweak those graphs, when I'm doing six or eight monitor mixes from 150 feet away it can be difficult to tell which wedges are squealing. Sometimes too, I'll ring the system to within an inch of its life at three in the afternoon and run all day like that, and after seven the air will change and I have to fix the monitors, remotely, on the fly, quite a lifesaver.

Bottom line: *USE YOUR EARS... PRACTICE PRACTICE PRACTICE*
And here's a link to a software feedback trainer that I've used some:
https://sourceforge.net/projects/sft/


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## SHARYNF (Nov 23, 2006)

Jon raises some good points.

Be a bit careful with using cans, since phasing errors tend to be masked but it does give you an idea of what the music should sound like minus room/speaker "alteration"

As he points out, over time you do learn to know what it should sound like, like a musician knowing when the instrument is in tune
Patchable rta for monitor mixes controlled from foh, can be a big help for quick find. As Jon points out, remember that temp and humidity have a significant effect on the sound. Dave Rat of RAT SOUND and Band Engineer for Red Hot Chili Peppers just wrote an article on this for "live sound"

Sharyn


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## Eboy87 (Nov 27, 2006)

Hey Jon, do you know if that program works for mac?


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## saxman0317 (Dec 1, 2006)

Number one, i dont beleive in the auto systems. They may come close, but im never really happy with the sound that comes off of it, but it may just be because of my music background. Now, i know that for alot of people doing EQ can be kind of difficult, but the first thing i do is go for nothing but making the actually pitches correct. To do that, there a few things you can do, depending on how perfect you want it. As a musician i have a good ear for tuning and just play a very good copy of anmazing grace my buddy recorded and use it as abase for the pitches and different instruments for different pitch ranges and frequencys. If im in a really perfectionist mood or if the systems going to be set up for awhile, i will run different pitches and adjust untill each pitch matches up with a tuner in the house. Also works good when working with mics. I like to do each mic individually like this with a standard pitch to give them all an equal center. Its amazing how off some mics are. And once you have the nitty gritty down for proper pitches and such, everything else pretty much falls into place.


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## stjc15 (Dec 14, 2006)

Another question. If I know the freq respnse of the speakers I am using, is it a good idea to cut the freqs on the eq board that the speaker cannot produce?


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## SHARYNF (Dec 14, 2006)

The answer is it depends

On the low end cutting off low frequencies that your speakers cannot reproduce is usually a good idea, it reduces the work load on the amp and adds a degree of protection for the speakers. Reason being that many times the speaker is actually attempting to move to support the frequency but is not able to generate that frequency, SO in general a low frequency cut off will improve things a bit.

A trick that is used in a lot of pro setups is what is called AUX subs, here what you do on your mixer is only assign those inputs that actually have low frequency content that you want to reinforce to that aux feed in addition to your normal out, you then take your normal mixer/rack out and feed that to your crossover dsp system that covers everything above your subs (typically in big systems above 80hz or so) you then only feed the aux sub feed to a crossover/dsp that only send the 80hz and below to the sub FROM the inputs that you want. This can really clean up you system quite a bit, keeps a lot of low end rumble out of the system and gives you more control.

On the High end I would not cut out the frequencies, freq response of speakers is measured in terms of a response curve, with a roll off, so if you cut the hign end frequencies you are going to also effect the frequencies below the cut off based on the slope of the crossover.

Sharyn


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## Peter (Dec 15, 2006)

Hmm... somethings probably not right if you have speakers that cannot produce certain frequencies... If that is truly the case you should look what the documentation for your speakers says to do with the signal your feeding them. If they have their own crossover or something like that, just feed them a non-shaped signal (dont try to do the crossover's job for it). 

What is much more common to do (in my experience) is to pull out a frequency that a speaker produces too well. This frequency often has something to do with the speaker cabinet size and other design parameters. I know I use one set of speakers all the time, and I always have to notch out the same three frequencies and they sound about 100 time better, and I get a ton less feedback.


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## SHARYNF (Dec 15, 2006)

I am assuming that the OP comment was regarding speakers that either do not have the low end range or the upper end range which is pretty typical, A lot of speakers don't put out much below about 60hz or so and roll off dramatically about 12k or so

so it does not mean that there is something wrong with the speakers

Sharyn


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## stjc15 (Dec 15, 2006)

Now, I am going to be eqing a system in a gym. I have worked a little bit with sound in there and I can't seem to get it to sound right. Are there any tricks, or is a room like that beyond making your system sound good? Our gym has an open balcony and is made of bricks, all flat of course. So echo and reflection is a real pain. Any suggestions?


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## SHARYNF (Dec 16, 2006)

your problem is not eq it is the room

Get your speakers up high, pointing DOWN at the audience, to reduce bounce back from the walls

If you can get drapes that you can hang around (commando 16 works great) it can make a big difference.

Lastly believe it or not if you can just borrow plastic wrapped bales of fiberglass insulation, and leave them all wrapped up and just stack them in the corners and in a few columns along a side wall it will help. Sometimes your local home improvement center will loan it to you, since you don't have to open them at all

Lastly, if you do this all the time, we on occasion use a series of curved panels that we hang from the ceiling, to reduce the reflections from the high areas of the gym, and keep the sound directed down to audience, sort of like a big band shell.

Sharyn


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## stjc15 (Dec 17, 2006)

I know that the room is a problem. I think the problem is a little of both. We are using the older PV SP-3's and I recently had to replace the woofers in them because one of them had been damaged. I figured a basketball or something hit it. Now that that problem is fixed, I am working on the sound. I am going to be talking to a company in our area to see if they will donate some sound baffling materials to the school to use in the gym. I will see if I can get the speakers to be pointed down a little. They aren't right now.


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## SHARYNF (Dec 17, 2006)

Think of the speakers like lights, the need to point and shine where you want the sound, NOT around the rest of the gym. I have seen endless setups where the speakers are just pointed out at the audience, the problem is the sound goes over their heads, bounces off the walls especially the back wall. Get the up high pointing down on the audience, then the sound absorption of the people will make a difference.

Sharyn


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## TomyN (Jan 18, 2007)

Hi,

in order to come back to the initial posting. In my experience the common RTA/pink noise measurement fails if the room is reverband or otherwise critical.
This happens because an RTA just averages over a longer period of time (which must be done to get stable results), but human hearing uses time to decide what sound is 'good' (which is the sound arriving first) and which is 'bad' (which is the sound arriving later). Because an RTA is 'timeblind' it can not decide which sound is good and which is bad. 
There are a lot of useful aplication for RTA, like ringing out or checking frequency content of a signal or detect feedback, but it is not 'state of the art' for equing a speaker room combination. 
Nowerdays I suggest a pc based system, like smaart(R) sim(R) or SATlive as the tool to use for speaker/room equing.
Nevertheless you must know what you're doing.

Be blessed

Tomy


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## jkowtko (Jan 20, 2007)

I also have a bit of a feedback problem in our little community theater. We hung the center cluster (for the first time ever) this past summer, and while it sounds pretty good in conjunction with the left and right wings (which I also just hung) it's about 10 feet back from the front of the circular stage front and we do get feedback from the actor's mikes from time to time. The "better" actors with louder, more level voices come out fine, it's the actors with the weaker voices that I have problems with. Currently without spectrum analyzer (RTA?) or EQ my only resource has been to pull down the center cluster volume momentarily as needed to squash the feedback, and live with lower-than-required mic volumes for these actors.

The reigning suggestion seems to be to balance the mic not the room. So I would want an RTA that I can move between input channels during a show to see how each input is balancing and where feedback problems are occuring. Then I need a good EQ for the output ....

Fyi, I'm using a Mackie CFX-20 ... analog, 20 input channels, 12-16 live mics.

Questions:

1) RTA: any suggestions on what software (I will be able to get a PC if needed) or hardware to use for a spectrum analyzer? Preferably one that I can easily move between channels, or set up to several direct outs (we have inserts that can be used for this) or sub or aux outs, so I can quickly switch my monitoring between channels during the performance as needed?

2) EQ: For the output, do I plan to EQ the individual channels (we have 20), or the sub-outs to the speakers? I have four main house outputs (left, center, right, rears) so if the EQs work in channel pairs then presumably I would need two units.

Thanks. John


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## TomyN (Jan 20, 2007)

Hi,

are you satisfied with the sound of the vocals, and there is just a feedback problem, or is the sound not what you exspect?

If you have an anused aux, you can simply use the aux to feed the rta. Other posibility is to connect the RTA to the pfl signal, which might be done using the monitor output.

As the first step I'd assign an eq to the center cluster. 

If you're using a digital controller, you might also try to adjust the time differences between left / right and center.

Tomy

P.S. If you're sure that you only need an RTA then I'd go for a 19" RTA, otherwise I'd use a software solution (which also can help during EQ and delay setup). Threre are some software RTA's available. On the Allen&Heath pages there is a pure RTA software. Other software containing an RTA is smaart or SATlive (and a many other).


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## brucegoodman (Jan 20, 2007)

Most of the venues I work were not built for performance but to look pretty. Many gyms and community buildings. My goal is speech intelligability 1st and music second. 
The comment about the speakers being behind the stage is one I run into all the time. Architects love to put them there. But they can't be there and get the house to sound good. They become stage monitors. High speakers are the best idea where the rear listener is < 2 times the distance to the front listener. Then I add fills to the back. High again.
I have to do two ringouts. I use pink not white noise. I typically use an RTA with a test mic set in the middle of the room moving it front to back (max comb effect w/ L/R speakers) looking to see if I phase between 500hz and 3000hz. Cause thats the spot nobody can be heard/understood. I flat the eq first to see what my speakers can do, and I gar-on-tee two ways won't hit 300hz. I always have one eq per speaker and dump the low end with a hipass. Pay attention to the guy who spoke of the Q of an eq. Then I build a pink noise room curve per speaker. Bump the lows, flat the middle and tail off the highs. Then I set up mics and take down(with a parametric) at least the first 3 ringback freqs. Always being careful not to gain up or down too much because it will change the phase of the freq. Then I ring out my monitors much the same way. Rear Fills must be timed and sometimes I'll use timing to adjust comb for left right phasing. 
Actually, I left a step out at each point. I usually play/and have someone speek so I know it sounds natural and pure.
Then the lighting guys show up.


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## jkowtko (Jan 21, 2007)

Thanks for the previous replies. 

I am fine with voice quality in most cases -- it seems to me that most of this is up to the actor and there's not much I can do except play with the channel midrange and high end a little (I usually pull the bass down and I have the highpass filter on the input channel turned on).

I did download Allen&Heath's RTA program ... nice little program and seems pretty convenient to check out the acoustics of our room. 

However it looks like I'll probably need to buy a decent EQ ... maybe two if I want to manage all four output channels. Does anyone have suggestions on good (budget) EQs that will also allow me to notch down for feedback? I've seen them as cheap as $100 ... are those any good? Should a standard 31 band EQ work for this or is something else needed?

Thanks. John


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## audioslavematt (Jan 21, 2007)

Get yourself a dbx2231 and be done with it. They're rock solid and fairly cheap.


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## brucegoodman (Jan 21, 2007)

Let me reiterate that understanding the Q of an eq is essential and why parametrics are used to knock down feedback. Q is the bandwith affected by the eq. Feedback usually has a very specific center freq caused by the room dynamics. You want to lower the level of that freq. You don't want to change the gain or attenuation of freqs outside of this center. Cheap eq's gain or attenuate the freqs outside the center freq. Your ding is at 1112 hz. You can't pull that down with a 31 band eq, you pull down 1k until you're affecting 1112 hz, but now you've also pulled down 800 thru 1200 hz parabolicly. Like the other person said, parametrics adjust the freq center, the bandwith, and the depth of cut, minimizing feedback and an unatural sound.


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## jkowtko (Jan 21, 2007)

I have been looking at the DBX equipment -- thanks for the endorsement.

Question -- should I consider the iEQ31 instead, to get the feedback suppression notch filtering? I've heard a general sentiment against feedback suppressors, but these evidently have pretty narrow notch filters.

However, I notice the "short" filter lift time on this unit is 10 minutes ... with live musical theater it would be great to have something with a 10 to 60 second lift time since the moments of feedback exposure are so brief. The iEQ manual doesn't say if you can reset the filters on the fly ... do you know ... or is there another feedback suppression unit out there that will do this? This is, of course, assuming that you support live feedback suppression at all (and for that I am eager to hear the opinions of others ...)

Thanks. John


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## TomyN (Jan 21, 2007)

Hi,

I think you should forget those feedback 'killers', because actors move, and so this units must fail.
If do not use a systemcontroller device yet, I'd suggest to use some. This digital units are nowerdays cheap and have reached a fine audio quality. They normaly feature parametric eq capabilities, and (which I like most of all) delay capabilities. Disadvantage is that 'realtime' access to the eq is not so easy. Therefore you can use them just for a basic setup, but when you're fixed on one location, and your speakers do not move, this is not so bad.

I use a systemcontroller (for x-over and delays) device in conection with a digital eq (both liked using AES digital signal) for live sound.

Tomy


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## SHARYNF (Jan 22, 2007)

Just because the actors mhve does not mean the feedback surpressors will fail. The issue with feedback surpressors is that they are best as a quick and dirty, I don't have time to ring out the system OR in fact when the actors do move . BUT if the sound system is properly set up and run out, the only area for feedback problems will typically be monitors. Unless of course you have one of the non audio savey installs which insist in putting the speakers behind the stage lip

Sharyn


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## TomyN (Jan 23, 2007)

Hi,

in my experience a feedback-killer-device works only fine if basic equing is fine. The feedback killers act fine and quick on small peaks, which they suppress with a notch filter. But if there is a wider peak on transfer function, the killers just set one notch beside the other until there are no more notches left. 

So my suggestion is always:

First EQ and proper setup of it, 
second feedback killer as 'emergency break'.

Tomy


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## avkid (Jan 23, 2007)

$500 is fairly cheap?
http://www.sweetwater.com/store/detail/2231/


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## audioslavematt (Jan 24, 2007)

avkid said:


> $500 is fairly cheap?
> http://www.sweetwater.com/store/detail/2231/



When the company you work with most often has KT, Drawmer, and BSS processing, yes, a $500 EQ is fairly cheap. Now if you want cheap, go B******** (but that's another thread).


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## Yellow_Fuzzy (Feb 5, 2007)

Hi,

The company that I have been doing some work for recently uses FuzzMeasure(Mac Software, http://www.supermegaultragroovy.com/products/FuzzMeasure/) which plays a Swept Sine Wave through the speakers and records the response via a Measurement Mic. Then from looking at the response graph a XTA DP2000 & DP226 has parametric EQ's which are used to flatten out the response. From what I have heard of the system once tuned in both outdoor and indoor environment it works very well. Personally my boss much prefers the result from this method than from an RTA playing white/pink noise.

Regards,
Zac


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## tblan (Feb 19, 2007)

Really, the most important factor to consider here is phase, a topic that only a few people have touched on. The first thing you need to realize is that eq can only affect the output of your speakers, and is not an effective tool to correct room characteristics. An rta measures the acoustic energy at a specific instant in a specific spot in the room. For that reason, it is not very helpful when equalizing the system because it cannot distinguish direct sound (which you can control) from reverberant and reflected sound (which you can't control). A distinction needs to be made between rta's and programs such as SMAART and Spectrafoo, which utilize dual channel FFT and TDS (time delay spectrometry) to screen out reflections and compare the speaker output to the board output. Say for example you noticed a notch at 1 kHz. This could be due to a speaker irregularity, or due to a phase cancellation from a reflection. The simple rta would give you no indication as whether you need to apply equalization or consider acoustic treatment or repositioning some speakers. I'll leave it at this for now, out of consideration for space. For more information on this check out some Live Sound issues from a few years back (2003 rings a bell), they had a whole bunch of great articles on this.
Some other thoughts of mine from reading your posts:
*Boost frequencies with caution. Many engineers only cut frequencies, as a boosted frequency can serious cut down your headroom at the amps.
*Think of the graphic equalizer as a very blunt tool. Its good for addressing some general trends in the frequency response of the system, as well as for program equalization. To achieve a linear response, parametrics are the way to go. (However, in monitor world this is a whole different story)


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## Ghost (Feb 26, 2007)

i have found afew Beta software programs if you have a computer on hand. Sia Smaart is one of the best, Spectrum Analyzer Pro Live is a trial for 14 days and has sugested EQ functions that show you exactially what to add and remove for a digitally correct mix (just go by ear after that for tweaking)


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## TomyN (Feb 26, 2007)

Hi,

well there are other programs out there like SIM II(I), which I consider to be the best system for live audio measurement. An other one is SATlive, which can be used as a 30 day demo also.
I do not like 'equalisation suggestion' by software. I like to see the facts and then to make a desicion on my own.

Tomy


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## Andy_Leviss (Feb 26, 2007)

Ghost said:


> i have found afew Beta software programs if you have a computer on hand. Sia Smaart is one of the best



Just to clarify, Smaart 5 (Windows) is not beta, it's a few years old, but works quite well. Smaart 6, which is the first cross-platform (Mac and PC) version, is in Beta, due to be released March 15 or so. About the same time I'll be migrating from Windows to a Mac Book, hopefully, conveniently enough!

--A


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## jkowtko (Feb 27, 2007)

Argh -- it looks like I may need to go back to Engineering school ... just starting to read up on info from SATlive, SIA, Meyer. 

It looks like I could learn a lot about our theater's acoustics with one of these dual channel software analyzers, but seeing as how right now I don't have any detailed knowledge of this stuff and have no sound conditioning equipment whatsoever, is there an approach I should take here? 

And good white papers I can read first?

Any suggestions for what I should do with a 2-week free trial of an analyzer program, which will lead me to buy the right first piece of equipment?

Thanks. John


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## TomyN (Feb 27, 2007)

Hi,
as a starting point I'd suggest reading either one or more of the technical articles available on siasoft's homepage, covering different things, or the 'Timealignment using SATlive' pdf, which covers setting up the measurement system, measurement of delay and frequency response and adjusting the timealginment in a small subwoofer-Top configuration. This can be found at 
http://www.take-sat.de/download/timealignmentE.pdf
Those documents give you an overview what can be done using those softwares.
Tomy


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## Andy_Leviss (Feb 27, 2007)

If you explore both SIA's website and ProSoundWeb.com, you'll find a couple tutorials on Smaart that are worth reading. If you can afford it and are serious about it, Smaart School or Meyer's SIM School are well worth it. I've taken the former, and the latter is on my to do list; I've been told that since SIM is more complex, if you take SIM School, you'll be able to find your way around Smaart on your own, so it may be the better time/money investment.

-A


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## DarthFader (Mar 3, 2007)

stjc15 said:


> In my years of experience in sound, I have learned that it is important to eq your system. The problem is, I have never learned a good way to eq a system. How does everybody else eq their system? Which technique is the best?



Everyone has their own thoughts here, but here is what works for me.

First I use a laser to verify that my speaker aiming points are unchanged and correct.

I have a low end RTA. It doesn't really matter because I use it only to establish a starting reference point. The rig is permanently installed in the theater so I have located specifc points in each coverage area that I EQ to a flat response with the respective graphs. That helps compensate for changes in the theater like soft goods and other changes in materials or structure.

From that point there its a no substitute for listening and fine tuning. I keep a some digital pictures of the EQs and compare the new setings with the old when it all sems to be pretty good. If I see a radical change in any of the graphs, its sort of a nudge to go back to that area and listen again to be sure.

I'm of the school that the better the room and the installaton, the less EQ is needed or desirable. When you see huge differences in adjacent sliders on the graph to get the RTA to show flat it usually means there is a problem in room reflections or timing, not in the EQ. If you go back to that location and listen you will probably find that six inches away it is completely different. Time to back off the graphs and work on fixing the reflections or timing issues. If you've got more than one speaker and a completly dead room, you will never get all the issues perfect, but you can move them to where they do the least damage and do your EQ again.

I know that everyone hates to part with the $$$, but invitiing in an installation pro to apply some fresh ears and ideas to the system usually is a smart investment. If their job every day is resolving room and timing issues, they darn well should be better at it than the rest of us.


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## howlingwolf487 (Mar 3, 2007)

SHARYNF said:


> your problem is not eq it is the room
> Get your speakers up high, pointing DOWN at the audience, to reduce bounce back from the walls



Just be careful there...you can get reflections off the floor, too. EQ'ing a system for a "gymatorium" isn't fun nor is it easy. The amount of people in the room and where they are positioned or clumped together will usually have a large impact on the low-end response of the room. I know our auditorium (NOT a gymatorium) has to run a bit hot for the low-end until it fills with people. They suck about about 13dB of low end and level out the room reponse very nicely.


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## jkowtko (Dec 23, 2007)

A more experienced sound guy that came by a few weeks ago to help me EQ the room had a neat trick --

A CD with pink noise separated into the bands of the 1/3 octave EQ. Each track on the CD played a reference band alternating with one of the other bands, switching back and forth about once a second. Each track on the CD compared a different EQ band against the reference band.

This technique allowed him to select a CD track and tune each EQ band individually against the reference band. And you could definitely hear where the speakers were louder or softer than reference

If anyone else has used this technique I'd like to hear your thoughts.

Or, if there are other similar tricks out there that aid in balancing speakers in a room, please share!

Thanks. John


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## SHARYNF (Dec 24, 2007)

The method you have described is now typically considered not to be a good idea

In general you use the Graphic eq as a way to eliminate feedback in monitors, and IN the MAIN FOH speakers to correct for non linearity in the speakers themselves, NOT to correct for Speaker/room interaction. Attempts to do this result in serious distorted response curves, and typically are only valid at a single point in the room if anywhere. In general you are looking for responses issues in the speakers/ or the cross over and attempting to eliminate the room from the measurement
As a rule, use acoustic treatment of the room or speaker placement to correct for speaker/ room interaction. 

Sharyn


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## mixmaster (Dec 29, 2007)

jkowtko said:


> A more experienced sound guy that came by a few weeks ago to help me EQ the room had a neat trick --
> A CD with pink noise separated into the bands of the 1/3 octave EQ. Each track on the CD played a reference band alternating with one of the other bands, switching back and forth about once a second. Each track on the CD compared a different EQ band against the reference band.
> This technique allowed him to select a CD track and tune each EQ band individually against the reference band. And you could definitely hear where the speakers were louder or softer than reference
> If anyone else has used this technique I'd like to hear your thoughts.
> ...



John,
It is an interesting thought but I wonder how he decided on his "reference" bandwidth. 
I prefer to hear the whole spectrum when listening to a room, so I can hear the effects of what I'm doing as it applies to the "big picture". You see, each bandwidth you adjust interacts with the ones on each side of it. If you just listen to, say 80 hz and compare it to 160 hz, then adjust the 160hz to match, you don't really know what's going on at 140hz. Even if your next comparison is at 80 and 140 you never hear 140 and 160 together. There can be all sorts of stuff happening there. The interactions between frequencies is sometimes called "color" (As in: You've overdone the EQ and colored up the mix.) I can see his technique as a tool for finding and working on a specific frequency maybe, but not for a whole room response. The best tool you have is your ear. 
When I do a room with pink noise, I play the whole bandwidth, 20 hz to 20khz. I listen to the sytem and try to hear frequecies that stand out and notch them. At first you may need an RTA to help you visualize what's happening, but with practice you will tune your ears and learn to do it without the RTA. At that point you can say "the lower mids are killing me here" and work with a group of filters till you get it right. Eventually, you get to where you can hear a frequency and say "that's 250hz biting us, drop it by 3db" and all the young kids will look at you in amazment.
Play with it, and have fun.


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