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Sine Sweeps vs. RTA
Old 8th September 2019
  #1
Gear Head
 
Helvetica's Avatar
 

Sine Sweeps vs. RTA

I just finished tweaking my (professionally designed, treated) room. Adjusted speaker position, sub location and level, crossover freq. etc. I even added a little correction eq and I am very happy with the results. Sounds much better. So I took some measurements with sine sweeps. Looks as good as it sounds, not much more than a few dB of variation. While I was at it, I measured pink noise through an RTA (in REW). Totally different story. Approx. 25 dB difference between 100Hz and 10kHz. Can anyone explain this? Sorry if this has been answered but the only thread on GS that came close was a colossal thread which quickly devolved into math and bickering. Can I trust the RTA readings? Did I measure it incorrectly? TIA for any help.
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Sine Sweeps vs. RTA-l-r_average.jpg   Sine Sweeps vs. RTA-post-eq_rta.jpg  
Old 8th September 2019
  #2
Old 8th September 2019
  #3
Gear Head
 
Helvetica's Avatar
 

So… are you suggesting that I use white noise instead? It makes sense but contradicts everything I've had about doing this kind measurement. Can anyone corroborate this?
Old 9th September 2019
  #4
Lives for gear
 

It's correct. No errors. As the explanation at Jason's link explains (in technical terms), pink noise has the same energy in each octave of the spectrum. When you do a sine wave sweep, REW puts out the same power for each individual frequency, as it slowly scans up the spectrum, so the resulting curve appears to be flat: same intensity for each FREQUENCY. But when you tell it to generate pink noise, you can think of it as putting out all possible frequencies at once (instead of one at a time), and adjusting the power of each frequency such that it is generating the same power for every OCTAVE (instead of each individual frequency). Since the octave bands are logarithmic, with each consecutive band having twice as many frequencies in it as the band below, the same power is now spread across twice as many places, and thus the power for that band is lower than the power for the previous band: therefore, the curve is "tilted" to the right. Because the same amount of power is spread out over a wider area of the spectrum as you go up in frequency, and thus the power for each individual frequency is lower. The slope of that curve should be 3 dB/octave (assuming you are measuring power).

So your room tuning is fine. That's a pretty good result, actually! You seem to have around +/- 3dB frequency variation, or better, which is not easy to achieve. Nice!

You might want to consider applying a house curve, similar to the famous B&K curve from many many years ago: Some engineers prefer to have that slight bass boost and slight treble roll-off, as they say it is easier on the ears for long sessions, and sounds a bit more natural than totally flat. Some people don't like "flat", and say it is too "clinical". Others love "flat", and would not have it any other way! That's more of a personal preference, actually: the conventional specifications for control rooms do specify "flat", and you are meeting that, so if you are happy with it then that's great! No need to change. But if you feel that the high end is slightly "live" or "harsh", and the low end is a little "dull" or "lacks punch", then you could try adding a house curve. It's very subtle, though! Don't go crazy! Just very minor changes.


- Stuart -
Old 9th September 2019
  #5
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Jason Foi's Avatar
 

Quote:
Originally Posted by Helvetica View Post
So… are you suggesting that I use white noise instead? It makes sense but contradicts everything I've had about doing this kind measurement. Can anyone corroborate this?
No, im saying everything looks correct.
Old 9th September 2019
  #6
Gear Head
 
Helvetica's Avatar
 

Jason and Stuart. Thank you for your expertise. I am feeling much better about these measurements now. You guys rock.
Old 9th September 2019
  #7
Lives for gear
https://www.roomeqwizard.com/help/he.../spectrum.html

Have you read the rew help?

Use pink pn sound, use the average and let one minute before stop.
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