Speakers distortion

[RayDunzl]

Gotta do some work, will return in a couple of hours (and delete this notice)

 

[Krunok]

Interesting "broad base" there.

Try no averaging?

55dB is low - try 75 or whatever you're comfortable with.

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Oh, I see, the broad base is a remnant of the beginning of the tone. Forever average and only 15 of them.

Reset the averaging - best way seems to be to turn the red button top right off and on again while the tone isn't stopped when averaging.

I don't understand. Shell I set averaging to some other value than "Forever"?
I reset averaging before every measurement.

It is not 55dB, volume on Volumio is cranked to 82 out of 100. I have no idea why it is showing such low value as 55dB as speakers are certainly producing much more than that at 82% of the volume.

 

[JohnPM]

Maybe some future version of REW will take room characteristic into account when measuring distortion..

REW already has an option to allow for responses that are not flat, tick the box to "Use harmonic frequency as ref".

Edit: this is for sweep measurements.

 

[JohnPM]

So, can I use the same log sine WAV file as I'm using for frequency response measurement?

No, you need to save a WAV file of a tone, e.g. 1 kHz, not a sweep. Also on the RTA you need to use a Window other than rectangular, such as Blackman-Harris 7.

 

[RayDunzl]

REW already has an option to allow for responses that are not flat, tick the box to "Use harmonic frequency as ref".

I don't understand that option.

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Also, the current beta - V5.20 beta 2 - seems to have some flaky operation, don't see mention of it in your forum. Another person here rolled back to a previous version.

 

[Krunok]

No, you need to save a WAV file of a tone, e.g. 1 kHz, not a sweep. Also on the RTA you need to use a Window other than rectangular, such as Blackman-Harris 7.

I used sweep to get distortion in the "Distortion" pane. It's shown here.

I will now try with the WAV file as you explained - thank you for helping me!

 

[Krunok]

No, you need to save a WAV file of a tone, e.g. 1 kHz, not a sweep. Also on the RTA you need to use a Window other than rectangular, such as Blackman-Harris 7.

I got this. Is that ok now?



If I press Save how can I again get the same data in this view?

 

[JohnPM]

I don't understand that option

If Use harmonic frequency as ref is selected the reference will be the frequency of the harmonic - for example, at 1 kHz the 2nd harmonic figure will depend on the level of the fundamental at 2 kHz, the 3rd harmonic will depend on the level of the fundamental at 3 kHz and so on. This follows a recommendation made by Steve F. Temme in "How to graph distortion measurements" presented at the 94th AES convention in March 1993.

Also, the current beta - V5.20 beta 2 - seems to have some flaky operation, don't see mention of it in your forum.

Depends what you mean by flaky, I'd need something a little more specific . Here are the things I know about that are fixed for beta 3:

[*]Bug fix: Calibrate soundcard wouldn't work on macOS
[*]Bug fix: If the sig gen had not been launched calibrate soundcard would fail to play the 1kHz tone and check levels would not work
[*]Bug fix: Output level was not shown on VU meter when measuring with a 4M sweep

 

[JohnPM]

I got this. Is that ok now?

Looks good, may want to use Spectrum rather than RTA mode though.

If I press Save how can I again get the same data in this view?

The distortion data is in the notes for the measurements that is created.

 

[Krunok]

Looks good, may want to use Spectrum rather than RTA mode though.

How do I do that? Is it different than the first distortion measurement I made here?

 

[Krunok]

This is how it looks for both speakers. My Castles fought hard and brave but couldn't come close to @RayDunzl Martin Logans.

 

[RayDunzl]

Depends what you mean by flaky, I'd need something a little more specific .

I know....

I will make a list - haven't specifically tested between old and new - can run both versions and illustrate differences (I don't think they are all in my head)

A few things I remember;

Measurement - fails to complete, or completes improperly, repeat, repeat, then ok
Phase measurement result has changed a bit
Impulse response doesn't time align itself properly, may be inverted
Step response looks wacked...

Several unexpected differences, maybe more...

I'll make a list with examples and give you a PM in a day or two...

I've been actively using it for a long time with a stable audio system, something seems to be odd...

 

[JohnPM]

How do I do that? Is it different than the first distortion measurement I made here?

The first setting in the RTA controls lets you choose between a Spectrum view or various RTA resolutions, spectrum is more commonly used for distortion plots.

 

[Krunok]

The first setting in the RTA controls lets you choose between a Spectrum view or various RTA resolutions, spectrum is more commonly used for distortion plots.

I see, thank you. So with RTA I should use "Spectrum" mode and "Blackman-Harris 7" window?

To which value should I set Averages?

 

[JohnPM]

Yes. The more averaging you use the more you will see the average rather than peak levels of noise components, won't make much if any difference to distortion components that are above the noise floor.

 

[Krunok]

Yes. The more averaging you use the more you will see the average rather than peak levels of noise components, won't make much if any difference to distortion components that are above the noise floor.

I understand. Is 16 averages sufficient or you would recommend higher value?

In your experience, do the distortion values you get for particular frequency with RTA correlate well with values you get from log sine sweep?

 

[JohnPM]

I understand. Is 16 averages sufficient or you would recommend higher value?

It doesn't much matter, affects appearance more than information content.

In your experience, do the distortion values you get for particular frequency with RTA correlate well with values you get from log sine sweep?

Yes, though the sweep has a higher noise floor unless very long sweeps are used.

 

[RayDunzl]

I have no idea why it is showing such low value as 55dB as speakers are certainly producing much more than that at 82% of the volume.

Are you using a microphone with a calibration file?

Or calibrating the displayed to another meter? (see the SPL Meter window "calibrate" button)

Or what?

 

[Krunok]

Yes, though the sweep has a higher noise floor unless very long sweeps are used.

Sweep file I'm using lasts 12 seconds.

Should I hold the mic steady at one position while doing RTA measurement or should I move it like when I'm doing MMM RTA frequency response measurement?

When doing sweep distortion measurement is it necessary to make several measurements from different positions and average it like when doing frequency response measurement or it is enough do do it from single position?

 

[Krunok]

Are you using a microphone with a calibration file?

Or calibrating the displayed to another meter? (see the SPL Meter window "calibrate" button)

Or what?

I'm using microphone with calibration file.
It would probably be the best to calibrate SPL in the SPL Meter window but I don't know how to measure reference SPL.