Help with REW RTA measurement on generated sweep - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 14 Old 01-17-19, 02:30 PM Thread Starter
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Re: Help with REW RTA measurement on generated sweep

Hi guys,

I am super excited as I managed to do my first hopefully proper measurement using the Pink PN + RTA method.

Here is what I did:

1. Used a Pink noise to set the volume of my AVR until the SPL showed 75 DB (that was 65 on the Master Volume for me)

2. Generated and saved a PINK PN sample 20Hz - 20k Hz -12 DB, Stereo, 24-bit

3. Ran a measurement with RTA with the following parameters (thanks John!)
- RTA 1/48 octave
- FFT - 65536
- Max Overlap 93.75
- Adjust RTA Levels


Here are the results with the 1/48 smoothing and the 1/3 smoothing. What do you think?
Attached Thumbnails
Help with REW RTA measurement on generated sweep-pink-pn-measurement-1.48-smoothing.jpg  

Help with REW RTA measurement on generated sweep-pink-pn-measurement-1.3rd-smoothing.jpg  


Last edited by kalohts; 01-17-19 at 03:01 PM.
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post #12 of 14 Old 01-17-19, 04:52 PM
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Re: Help with REW RTA measurement on generated sweep

Quote:
kalohts wrote: View Post
John, thank you for breaking it down for me. I did exactly as you said and configured as in your screenshot. However, when I hit measure, the sweep plays through my laptop speakers and does not wait for me to play the sweep as you describe. Is it possible that in the latest version I have installed this is no longer the case? (the waiting does not happen)
I can't provide a specific answer as I do not know your entire equipment setup and capabilities.

Basically, use any method you have available that prevents the REW output signal from going out through the system; route the REW output to an unused channel, unplug the REW output wire, mute the REW output channel, etc.

If the output of REW is shared with the music player on the same computer and you have no other direct way to mute the REW output maybe try setting the REW output volume initially to minimum (-90 dB). REW not be able to detect the generated signal and will have to wait until the file is played. You can then play the file with the music player using the appropriate volume. My setup does not have this problem so I have not tried this.

I just set the input mode of my AVR to my music player rather than the input that is connected to REW.
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post #13 of 14 Old 01-18-19, 12:10 PM Thread Starter
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Re: Help with REW RTA measurement on generated sweep

THANK YOU!

I finally figured it out how REW waits for the timing reference - very smart! I basically turned all the way down my laptop volume, so as REW starts it does not hear any sound coming out. Then I play the file from my AVR.

So here are my results. I used the measuring sweep in the Measure tool.

I do not understand much (yet), but I think on my stereo measurement my speakers output is generally flat up until 500Hz. Interesting is that my speakers measure quite differently... which I sort of expect. My left speaker is next to an open door - so an open space. The right speaker is limited to the right wall of my room which is about 9 feet away from it and probably some other living room stuff.

What do you guys think about the graphs? I have Graphic EQ on my AVR with 9 bands (63 Hz / 125 Hz / 250 Hz / 500 Hz / 1 kHz / 2 kHz / 4 kHz / 8 kHz / 16 kHz) but I am hesitant to tamper with them as I know that's totally different than Parametric EQ.
Attached Thumbnails
Help with REW RTA measurement on generated sweep-both-speakers.jpg  

Help with REW RTA measurement on generated sweep-left-speaker.jpg  

Help with REW RTA measurement on generated sweep-right-speaker.jpg  

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post #14 of 14 Old 01-18-19, 01:02 PM
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Re: Help with REW RTA measurement on generated sweep

That looks very good to me.
The individual speakers 500-20k response looks good. It is normally not recommended to make any adjustments there based on LP measurements anyway. The room influence changes the relationship of the SPL vs our perception of the sound. Our perception is more based on the direct sound portion of the total SPL measured. Both channels measured together is completely unusable as comb filtering is an additional big problem that impacts the upper end of the SPL response. It is responsible for the large sag centered on 7kHz on the L+R measurement.

Any EQ you want to try is best limited to the 20-200 Hz range. That should be viewed using no smoothing. You can used 1/24 octave smoothing to help decide the 1/3 octave GEQ setting, but then switch back to no smoothing to confirm the improvement. There is usually little that can help as it takes some luck for the GEQ to be able to help with the problem. If you can reduce the 65 Hz peak without causing other issues then that would help a little.

Basically is very good as is. The L+R 20-200 Hz measurement is ideal and that may be better than with any adjustment to the 65 Hz individual peaks. It depends is the bass of a particular recording is mono or in just one channel.

Just the thoughts of this hobbyist.
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