EQ Techniques-Suggestions

[brucegoodman]

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.

 

[jkowtko]

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

 

[audioslavematt]

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

 

[brucegoodman]

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.

 

[jkowtko]

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

 

[TomyN]

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

 

[SHARYNF]

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

 

[TomyN]

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

 

[avkid]

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

 

[audioslavematt]

$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).

 

[Yellow_Fuzzy]

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

 

[tblan]

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)

 

[Ghost]

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)

 

[TomyN]

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

 

[Andy_Leviss]

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

 

[jkowtko]

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

 

[TomyN]

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

 

[Andy_Leviss]

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

 

[DarthFader]

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.

 

[howlingwolf487]

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.