# Help to interpret results



## Macattack (Mar 20, 2013)

Hey folks, I have gone the route to set up a ECM8000 mic into a X502 and UCA222 into a Win Vista PC. I am able to make measurements and visually see the impact of speaker location changes (although the various controls on the X502 are somewhat of a mystery to me, I got it working). After much experimentation, I ultimately went back to locating my speakers within inches of where the Cardas formula says they should be (78" from back wall, 48" from sides) with my ears about 1.3 to 1.5 X the woofer distance (80"). Further, I have 'tuned' the LF eq of the Infinities to get as flat as possible. There are many, many variables but where I am at now seems to sound good, measure as good as I can seem to get it but does have some issues. The bump at 150 to 220 seems to be a room resonance (right?) and I cannot, no matter what I adjust, increase the upper mids \ highs to reach the same level as the low end. 

I have attached the .mdat file in the hope that you all can provide suggestions on where to go from here. Specifically how room treatment (and what treatments) can tame the bump up at ~150 to 220Hz. 

My room is 8.3' H X 14.8' W X 20.3' L. Open joists with 3" fiberglass on the ceiling, all other surfaces are solid concrete except for the wall behind the listener, which is a combination of an open door and drywall in an irregular pattern. The side walls are lined with shelving that contain a variety of irregular soft and hard surfaces and the odd hanging moving pad at primary reflection points . I intend to finish this room so not necessarily making it perfect in its present state. 

I really want to learn how to interpret what I see from REW in this two channel system to optimize location and room tuning before I go upstairs to 'theater' where things will be much more complicated by fewer degrees of freedom. These measuremnts are for the 2 channel system. I am not interested in any outboard equalizers.

After reading last night about the house curves and the theory of it, I think I will push the LF eq of the Speakers up a nudge and should, with smoothing, get a more balance sound. 


Thanks!


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## JohnM (Apr 11, 2006)

Measurement is good, you look to have everything working well on the REW front. Response looks good as well, but I'll move this thread to the acoustics forum where you'll get better advice on treatments


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## Macattack (Mar 20, 2013)

JohnM said:


> Measurement is good, you look to have everything working well on the REW front. Response looks good as well, but I'll move this thread to the acoustics forum where you'll get better advice on treatments


Thank you John.


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## Macattack (Mar 20, 2013)

Bump


Any thoughts on what I can to tame the 150 to 200 Hz bump?


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## Macattack (Mar 20, 2013)

Nobody?


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## EarlK (Jan 1, 2010)

Macattack said:


> Nobody?


Consider going the route of the following thread starter ;  *GIK Acoustics = Wow .*  The easiest route by far .

or ----

GOOGLE Search for ;  *Making Superchunk Bass Traps*  

or -----

Tutor yourself to acquire the necessary knowledge to arrive at similar conclusions ( as GIK ) through buying ( & reading a couple of the following reference books ) ;





Also, download the following pdf file ( to get an idea of how the look of certain measurements, "translate" into a good listening experience ) ;  *AMS parameters for Stereo Listening* 

:sn:


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## Macattack (Mar 20, 2013)

Thank you.


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## jim1961 (Apr 8, 2011)

It looks that mdat data is at 1/3rd oct smoothing. Need to see 1/24th oct smoothing.


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## Macattack (Mar 20, 2013)

jim1961 said:


> It looks that mdat data is at 1/3rd oct smoothing. Need to see 1/24th oct smoothing.


Ask and you shall receive.


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## jim1961 (Apr 8, 2011)

This is what I am getting at 1/24th oct smoothing.

I would say your getting some med/strong reflections causing the jagged looking curve. An ETC should reveal what those reflections are.


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## Macattack (Mar 20, 2013)

I appreciate you engaging in this. 

I am quite adept at following instructions, connecting things and executing but I am not an audio engineer. I can see what the measurements are and am trying to connect them to what I hear and then what I can do about it. I hear blooming sometimes in lower\mid register vocals (think Kathy Mattea) and a brightness to the overall sound. The measure seems to support the blooming but not the brightness as it is in general -5db below the lower registers. 

What is (an) ETC? Is it related to the RTA measurement and does that also help determine what the reflection frequencies are?


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## jim1961 (Apr 8, 2011)

Macattack said:


> I appreciate you engaging in this.
> 
> I am quite adept at following instructions, connecting things and executing but I am not an audio engineer. I can see what the measurements are and am trying to connect them to what I hear and then what I can do about it. I hear blooming sometimes in lower\mid register vocals (think Kathy Mattea) and a brightness to the overall sound. The measure seems to support the blooming but not the brightness as it is in general -5db below the lower registers.
> 
> What is (an) ETC? Is it related to the RTA measurement and does that also help determine what the reflection frequencies are?


ETC stands for Energy Time Curve or Envelope Time Curve. 

They look something like this:









They show reflections as amplitude in a time domain. They dont tell you where in your room the reflection is coming from or the frequencies associated with it. But those can be derived from the ETC using various other methods.

Nulls and peaks in the frequency response are always caused by reflections above the modal region. Often times what we perceive as too much or too little in some frequency range is due to the jagged and/or unevenness nature of the FR curve. 

If you were to run your FR response with no smoothing at all, I suspect you will see the peaks and valleys greater than they show even at 1/24th smoothing. When a musical note corresponds exactly to one of these peaks, it will sound loud and unbalanced even though the average response looks reasonable. 

From 4k to 7k, you have a 8db elevation in high frequency content. You also have a hump at 13k. These could be what your hearing in the upper range. Their could also be comb filtering at these frequencies which causes those frequencies affected to sound harsh.


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## Macattack (Mar 20, 2013)

Yes, lots of sharp valleys and 'rolling' peaks. I assume the shelving units with a wide variety of things on them AND the concrete walls are the cause of all of this. 

I started today to develop my design ideas and a list of materials to finish this room. That will include acoustic panels. Haven't decided on the exact measurements yet but will shoot for an optimal ratio that is as big as I can make it. (Still need storage there)

Have to learn more about comb filters. 

Thank you for your help.


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## jim1961 (Apr 8, 2011)

With no smoothing, it is to be expected to have lots of sharp jumps, especially in the higher regions. Its a matter of looking at it and knowing how much is acceptable and not. 

Any flat surfaces which by angle cause sound to reflect to the listening position are potential culprits. Shelves with lots of stuff on them are harder to simply look at and know what damage they are doing.

The ETC is the way to go when trying to deal with and track down reflections. The FR graph just isnt a good tool for it. Most of those I hang out with actually feel the ETC data is more important than the frequency response.

Food for thought


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