Posted by Julien43 (A) on March 26, 2007 at 18:11:35

As I posted earlier I planned on using five 2' X 4' X 4" OC 703 panels
Four are placed across the front and rear ceiling/wall corners, against the side walls
The fifth is behind my listening position

I have two 15" X 5'(front corners) and two 12" X 4"(side walls) ASC type traps. My measurements were taken with the same software, @ 80db. The only differences between the two graphs is that an ECM8000 Mic was used for the second measurement after the panels were installed and an old RS SPL meter did the duties for the first measurement. The proper calibration files were loaded for each measurement

I can't believe the extension the second graph shows because I am not driving my Gallo Reference3's woofers second voice coils.

I am planning to minimize any humps with a DEQ2496 when I get the room as good as I can(with in my limits)

Can you tell me what is going on here??

Here's the original graph

This one is after the panels were installed

Thanks for your help!!

Julien
"There's someone in my head, but it's not me"

• Re: 4inch 2' X 4' OC 703 panels Before and after measurments - Ethan Winer 10:56:33 03/27/07 (3)
  In Reply to: 4inch 2' X 4' OC 703 panels Before and after measurments posted by Julien43 on March 26, 2007 at 18:11:35:

  Julien,

  > Can you tell me what is going on here?? <

  You can't measure a room one day, then measure again another day - with a different microphone no less - and expect a valid apples-to-apples comparison. The main problem is the low frequency response in a room, even when treated with bass traps, varies a lot over very small distances. Even four inches away the response will be very different. I'm sure this is the main reason for the large changes.

  Also, a better way to assess the improvement from adding bass traps is to look at waterfall graphs. This way you can see the reduced ringing after adding traps, even if the magnitude of the response at different frequencies changes. Since you have the data in REW form there's no need to measure again - just switch to the waterfall plots.

  --Ethan
  
  

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  • Re: 4inch 2' X 4' OC 703 panels Before and after measurments (with waterfalls) - Julien43 15:22:34 03/27/07 (2)
    In Reply to: Re: 4inch 2' X 4' OC 703 panels Before and after measurments posted by Ethan Winer on March 27, 2007 at 10:56:33:

    "You can't measure a room one day, then measure again another day - with a different microphone no less - and expect a valid apples-to-apples comparison. The main problem is the low frequency response in a room, even when treated with bass traps, varies a lot over very small distances. Even four inches away the response will be very different."

    I'm still amazed at the huge change in tonal balance with each step I take while walking across my small room!

    I loaded the appropriate calibration files for each mic, so that should help make the results a little more comparable.

    Here are the plots

    This is the first measurement

    
    
    

    Here is the measurement after installing the panels

    
    
    

    Well, the second graph looks a little cleaner, I don't really know how to interpret what I'm seeing, let alone the best way to improve the situation(besides squeezing in more traps)

    I am going to get two 2'X4'X2" panels for the side wall first reflection points. I have my 12"X4' ASC type traps there now.
    That would free up those traps to be placed for better effect
    When finances and time allow, I will install two more 2'X4'X4" panels across the sidewall/ceiling corners

    Thanks for taking the time and effort to share your knowledge and experience!!

    
    

    
    Julien
    "There's someone in my head, but it's not me"
    
    

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    • Re: 4inch 2' X 4' OC 703 panels Before and after measurments (with waterfalls) - Ethan Winer 09:13:26 03/28/07 (1)
      In Reply to: Re: 4inch 2' X 4' OC 703 panels Before and after measurments (with waterfalls) posted by Julien43 on March 27, 2007 at 15:22:34:

      Julien,

      Those graphs are different enough that you should measure again if possible. But this time leave the microphone where it is between the With and Without tests!

      --Ethan
      
      

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      • Re: 4inch 2' X 4' OC 703 panels Before and after measurments (with waterfalls) - Julien43 07:04:33 04/01/07 (0)
        In Reply to: Re: 4inch 2' X 4' OC 703 panels Before and after measurments (with waterfalls) posted by Ethan Winer on March 28, 2007 at 09:13:26:

        "Those graphs are different enough that you should measure again if possible. But this time leave the microphone where it is between the With and Without tests!"

        That would be a major pain in the arse
        I'll just have to wait until I'm ready to make my next round of treatments to get accurate measurements of before and after

        Thanks again for your help

        
        Julien
        "There's someone in my head, but it's not me"
        
        

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