REW-Moving Microphone Method Help

[ppataki]

Yes, I did it again, same results

 

[markus]

Yes, I did it again, same results

How large is the area you're covering with the mic?
What results do you get when you just hold mic at a single location?

 

[ppataki]

Approx a 30cm sphere
The one-point measurement is the other graph you can see in my screenshot

 

[markus]

Approx a 30cm sphere
The one-point measurement is the other graph you can see in my screenshot

Was the one point measurement also done using the RTA with a noise signal?
Did you hold the mic in your hands for the one point measurement or was it on a boom stand?
Do 4 more one point measurements 15cm left, right, up, down from middle of the sphere and post the results.

 

[Pio2001]

Am I doing anything wrong or the MMM is not really to be used for measuring below 200Hz?

MMM is very accurate in low frequencies. Something strange happened in your measurement.

 

[markus]

MMM is very accurate in low frequencies. Something strange happened in your measurement.

The problem with RTA measurements is that they are susceptible to noise, especially at low frequencies and when the mic is hand-held. That's why I asked ppataki for more data.

@ppataki
Here's a more detailed description how to do the measurements: https://mehlau.net/audio/room-correction-peq/

 

[dasdoing]

The problem with RTA measurements is that they are susceptible to noise

yea, the sweep was introduced for a reason.
personaly I see no advantage of the MMM whatsoever.
I once took several meassurements to the left, and to the right. the average matched the 1 center meassurement with the var filter

 

[markus]

yea, the sweep was introduced for a reason.
personaly I see no advantage of the MMM whatsoever.
I once took several meassurements to the left, and to the right. the average matched the 1 center meassurement with the var filter

Unfortunately not true for each and every room. MMM is usually used to cover larger areas, not just a single listener area. Here it is way faster than taking a multitude of single sweeps. On the other hand you're losing phase information which might be of interest for a more detailed acoustical analysis of a particular room.

 

[dasdoing]

way faster

how many times a year do you take those meassurement though?
this is an issue for PA setups, not for home aplication

 

[Blumlein 88]

You see similar results comparing sweeps and MMM results here:
https://www.audiosciencereview.com/.../mmm-vs-sweep-rew-of-my-jbl-e80-towers.16966/

And here:
https://www.audiosciencereview.com/...ings-vs-impulse-convolution.13609/post-412457

For smaller MMM sized movements, smoothing may be just about as good with a sweep. MMM was developed for larger movements in larger spaces like theaters and areas with big PA systems.

 

[markus]

how many times a year do you take those meassurement though?
this is an issue for PA setups, not for home aplication

If you're an installer, hopefully pretty often And, for some enthusiasts it's a hobby. Anyway, the question is what data one wants or needs to obtain. MMM is just a tool in one's toolbox. Nothing good or bad about it per se.

 

[Chromatischism]

There are some settings you can't determine from the video. If you want it to look as shown in the video, you need to go into Appearance and uncheck "Use bars on RTA", and check "Adjust RTA levels". Took me a while to figure out why my RTA was so far off from my sweeps.

I am also using Pink Periodic noise, Full range, with:

Mode: RTA 1/48 octave
FFT/Sequence length: 32k
Averages: Forever
Window: Rectangular or Hann
Max Overlap: 50%, not sure if it matters

I measure speakers at 75 dB using the 90 degree calibration, mic pointed upwards. It's easier when you get near chairs, etc.

 

[Chromatischism]

One thing I'm finding really annoying is that a bump to the USB cable spikes the measurement and I have to start over.

 

[Evozero]

Hi All,
Just trying to get familiar with measuring and creating filters and have a hit a roadblock.
I have Moode 7.2.1 with CamillaDSP running on RPI4, USB to Topping E30 DAC.
Using my Mac and RCA cables to my amp, to run REW MMM and export WAV file filters then import into CamillaDSP. This process functions correctly.

My problem is how do I remeasure in REW with the filters applied?
How do I perform the measurements as the REW sweep signal is coming from the Mac not via the RPI with the filters applied.

Can I apply the filters REW creates on my Mac and retest from within REW?
Am I being stupid, I'm confused?

Thanks for any advice.
Ian

 

[Matias]

Hi All,
Just trying to get familiar with measuring and creating filters and have a hit a roadblock.
I have Moode 7.2.1 with CamillaDSP running on RPI4, USB to Topping E30 DAC.
Using my Mac and RCA cables to my amp, to run REW MMM and export WAV file filters then import into CamillaDSP. This process functions correctly.

My problem is how do I remeasure in REW with the filters applied?
How do I perform the measurements as the REW sweep signal is coming from the Mac not via the RPI with the filters applied.

Can I apply the filters REW creates on my Mac and retest from within REW?
Am I being stupid, I'm confused?

Thanks for any advice.
Ian

Play pink noise through your regular payback chain with DSP enabled, and measure with REW's RTA.

 

[Geert]

Or create a measurement sweep in the Generator window, save to disk and transfer to RPI.

 

[Evozero]

Thanks for the reply.
I was just reading that I can save a sweep as a WAV file and copy it to my RPI, but I have been following the MMM guides in this thread using RTA in REW, I am trying to do comparison MMM measurements?

Still confused

 

[Geert]

The principle still stays the same. But you manually start the measurement sweep on your RPI, and configure REW to start the measurement using the acoustic timing reference.

 

[Evozero]

The principle still stays the same. But you manually start the measurement sweep on your RPI, and configure REW to start the measurement using the acoustic timing reference.

Thanks thats helpful, create a sweep file for each channel and use a timing ref on one.
I understand transferring the sweep to the RPI as a wav and measuring with UMIK1+REW on the MAC

Still confused if the MMM RTA measurements will compare to a pink noise sweep, do I need to use specific sweep settings to compare them?
Thanks again

 

[Geert]

Now I'm getting confused ... Did you make the initial (before) measurement with a REW measurement sweep or with a MMM using pink noise?

Just create the same signal you used initialy in the REW Generator and use that on RPI to remeasure.