# Tuning an auditorium



## reflect23 (Jul 21, 2011)

I am Biamp AudiaFlex certified. I have a lot of experience with programming DSPs but have never had to tune a system (most of the work I do is for courtrooms where some basic defaults sound pretty good and only voice is usually involved. 

I have been contracted out to tune a few auditoriums because they are based on Biamp DSPs. I informed the person that contracted me for this job that I had no prior experience with tuning a system but I could find out the process and get it done. I do have a pretty good ear for audio from previous car stereo installations. 

I guess my point i that I have no idea what I am doing for the tuning but they tune these systems once a quarter. They want data of before work and after work spectrum analysis files, in word and/or excel detailing graphic and numeric sample results. They want these done at multiple points in the auditoriums and have specified exactly where the tests need to be performed at. I have installed REW and have read several posts here as well as the guide that has been prepared for using the software. I have a behringer uca202 external sound card, a decent dell laptop, and a behringer ecm8000 microphone with an extron mvc101 mic preamp/volume controller. Can anyone possible tell me what kind of readings I should be looking for with this setup? And if it sounds like I should have everything I need? I can tweak the equalizer settings in the biamp programming with no problems but I don't really know what kind of output I should be looking to achieve at each point. 

Thank you.


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## reflect23 (Jul 21, 2011)

I guess really my main question is, What kind of levels should I be shooting for? I am planning on doing a sweep and pinknoise tests. Should I be going for a flat response? Or a type of room curve? I've tested my setup in my house and everything appears to be working well.

Sorry for replying to my own post, I just thought I'd clarify what I am trying to ask.

Thanks


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## EarlK (Jan 1, 2010)

Wow ( such naivete, but at least you're asking for help ), I suggest that you immediately order these two books;

  
and

   

- using Amazons fastest shipping option .

*IMHO ; *
> You're in way over your head . 

> Once you have both these books in hand ( with at least a modest perusal under your belt ) you'll see that the  * "articulation constant / loss" * of large room acoustics ( the ability of speech to be understood within an acoustic environment ) is largely dictated by that rooms RT60 time / along with the implementation of a properly designed audio system ( that's been engineered to overcome/complement those same room acoustics ) .

> One can't EQ out the natural reverb times of big spaces ( this must be done with room treatments ) / though one can play the "avoidance game" ( identifying frequencies that have unusually long reverb times and then using EQ to pull those frequencies back a bit within the sound-system ) . 
> The concept of "giving everyone a speaker at their lap" works wonders in overcoming room acoustics ( though is highly impractical ) . 

> At this point in time I don't think you have enough evidence to confidently believe that those existing sound systems can do a proper job ( apart from others say-so ) . 

> Situations like you are entering into, can quite easily turn into one of ;  *"Being Thrown Under The Bus"*  ( whether through the malice of others or through others sheer ignorance of acoustic realities ) .

:spend::yikes::spend:


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## EarlK (Jan 1, 2010)

> I guess really my main question is, What kind of levels should I be shooting for? I am planning on doing a sweep and pinknoise tests. Should I be going for a flat response? Or a type of room curve? I've tested my setup in my house and everything appears to be working well.



*LEVEL :*
Tune the room to the normally used ( expected ) level of the playback type ( see below ) . 

*ROOM CURVE :*
(i) I'd build a preset for voice , truncating the LF below 100hz and above 5K ( sloping off at maybe 12db per octave ) .

(ii) Another preset for "canned" music might use the movie industries







 *THX "X-curve" * .

(iii) Another preset for live music might be essentially flat up to 10K or 12K ( allowing the sound mixer to choose the final spectral result ) . If his mix sucks ,well, the sound guy gets "thrown under the bus" ( but hey , at least you didn't deny him a full-range opportunity to get it done ).

<. EarlK


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## reflect23 (Jul 21, 2011)

Awesome, thank you both so much. I will get those books ordered asap.


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## Wayne A. Pflughaupt (Apr 13, 2006)

As Earl noted, you can’t correct acoustical issues with equalization. If the room is problematic the best you can do is “shape” the room response curve to give an assist for voice, music etc. Your car audio experience won’t help you here. Pro audio systems in public auditoriums are a whole ‘nother world. 

Have you personally visited these sites to see what you’re getting into? It’s absolutely stunning how many public auditoriums are built without any consultation with a professional acoustics specialist. It’s actually the exception rather than the rule. Churches are especially notorious in this regard. As a result, excessive reverberation and/or slapback echo are recurring and common issues. 

If I were you, before agreeing to this project I’d at least go and personally check these places out. All you need to do is stand somewhere in the seating area and speak loudly or clap your hands a few times. If your noise-making has a long decay time (excessive reverberation) or bounces right back at you (slapback echo), you’d be smart to take a pass, as there is nothing you can do from a “proper” system set up or EQ perspective that will make an improvement. There’s no miracle cure or magic bullet that electronics can offer to fix a room like that, and they’re going to hold your feet to the fire when they don’t get the (unrealistic) results they’re looking for.

On the other hand, if the room seems to have good acoustics, then a proper EQ and “room tuning” can make a difference - assuming they have a capable and well-designed sound system. Which is a whole new topic for another day...

Regards,
Wayne


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## reflect23 (Jul 21, 2011)

awesome, thank you Wayne. My understanding of this project is that other people have tuned the system in the past and that they do it on a quarterly basis... (Maybe I am being naive here but I would assume that once it's tuned, you shouldn't have to go back and tune it again unless equipment changes or something?) This install has been in place for at least a couple of years now. I am unsure of who originally set it up though and its history. I will definitely go take a look at it this week and do the echo test with speaking loud and clapping. My understanding of what they want me to do is to just make some minor equalization adjustments and take before and after snapshots of the acoustic measurements, one room with 12 points of measurements and the other with 6 because it's smaller.


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## reflect23 (Jul 21, 2011)

I never made an update to this, so I will do so now :
Things ended up going really well. Whoever originally tuned/programmed the system had eq settings going through bitrate devices (the name escapes me) and through a eq in the Biamp Audia DSP. It was apparently adjusted to make up for some blown amplifiers so when the amps were replaced, they had to tweak levels on a mixing board to absurd values to make things sound decent. I turned off the eq on the bitrate devices and flattened out the eq in the biamp then started tweaking from different positions in the auditorium to verify the response. They tested the microphones out and found that they had to "zero" everything out (as you should) and the difference was night and day. I used REW for my measurements from a before and after stand point. They have since asked me to come back to do some work when they replace some of the speakers. Both rooms were relatively new and designed with the assistance of audio engineers. 
TL;DR: I went in and turned off EQ from a set of bitrate adjusting units, zero'd out the input levels, re-did the EQ in the biamp and everything turned out great. It (the large auditorium)now sounds amazing.


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## reflect23 (Jul 21, 2011)

all tuned with REW, and a Behringer ECM8000 mic. :-D


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## Wayne A. Pflughaupt (Apr 13, 2006)

Thanks for getting back to us, reflect - happy to hear that things went well! :T

Regards, 
Wayne


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