Posted by Ethan Winer (M) on March 27, 2007 at 10:56:33

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

• 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"
  
  

  ---

  • 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
    
    

    ---

    • 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"
      
      

      ---

Post a Followup: