High measurement distortion

[PK1]

I’ve just begun setting up and measuring REW, but I continue getting a “The measurement distortion is very high” notice, and it ranges somewhere between 10-14% depending on the sweeps. My system:

- REW is installed on a Windows PC
- A Umik-1 is connected to the usb port of the PC, and I am using a 10’ usb extension to allow the mic to reach my listening position
- The output is connected from the USB-C port of the PC to the USB-C input of my DAC (SMSL-SU10). This USB-C cable is about 6’ in length
- The connection from the DAC to my Pre-amp (Ladder Bach), and from my pre-amp to the power amp (Arcam PA240) are all balanced XLR
- I have two REL subwoofers connected to my speakers through the high level input connection, but I get the distortion notice regardless of whether the subs are powered on or off

Any suggestions on where to look to address this?

Thanks!

 

[John Mulcahy]

Look at the distortion graph to see what that shows.

 

[PK1]

Look at the distortion graph to see what that shows.

Will do. I interpreted the message as a warning to fix something in the connections (picture of it below). I didn’t realize the graph could hold the answer. I’m very new to all of this…

I’ll run it again when I get home, I’m out at the moment.

 

[PK1]

I tried it again after I got back, and this time I get no distortion messages! I have attached the distortion graphs anyway in case something stands out.

I have also attached the SPL-Phase graphs. What is strange is that although I have set the system volume to measure around 75dB output, the measurements on the graph show closer to 80dB.

I calibrate the level using the system volume, and when the level settles around 75dB I leave he volume at that level. But if I turn the noise generator back on, the level starts reading at around 80dB and slowly comes down to 75dB without me touching the system volume. Is this normal behavior?

First and second graphs are distortion for L and R, and the third SPL/Phase

 

[John Mulcahy]

A distortion graph image doesn't convey much if it doesn't show any of the distortion data . Below 80 Hz or so the result is in the noise floor, so noise will register as distortion there and could trigger a warning.

 

[PK1]

Clearly I must be doing something wrong. All the boxes at the bottom of the graph are ticked, so I would have thought it shows all the harmonics unless I am not recording correctly. Is there something I need to activate/enable or am I doing something wrong in the recording process?

 

[dcibel]

Where do you expect the harmonics to be? Scroll down on the graph...

 

[John Mulcahy]

You can adjust the graph range by clicking the "Limits" button at the top right of the graph or moving your mouse over the ends of the axes and using the scroll wheel.

 

[PK1]

Where do you expect the harmonics to be? Scroll down on the graph...

I don't know where harmonics would be. I had assumed, clearly incorrectly, that the limits on the graphs would automatically be set to show the relevant data in the output view.

I am new to all of this and just trying to get set up first so that I can be able to get measurements and then read up on things and learn as I go along. I was getting some distortion warnings which sounded to me like a connection problem or a wrong setting somewhere which is why I posed the first question.

Changing the graph limits this is what I get. Not sure how to interpret it but will read up on it. When I ran this yesterday I was no longer getting the high distortion warning, if it comes back I'll need to figure out where it' coming from.

 

[PK1]

You can adjust the graph range by clicking the "Limits" button at the top right of the graph or moving your mouse over the ends of the axes and using the scroll wh

Thanks!