Speakers distortion

[Blumlein 88]

I think it's time for everyone with the capability to do some you close measures using REW.

 

[Krunok]

Thanks, I think the link is broken though.

Sorry, I corrected the link, it should work now.

 

[Krunok]

I think it's time for everyone with the capability to do some you close measures using REW.

Well that would be something, as then we would have some real stuff to compare!

 

[Krunok]

Well you can get a fair impression of this new world by using in-ear monitors, head tracking systems, computer game audio synthesis etc. The main limitation isn't a bit of distortion in the transducers, nor how the audio gets to your brain, but the recording/synthesis of the material you're listening to.

You can't record real acoustics such that you can reproduce them perfectly later, except from one position in space.

I dont agree. If we would be able to understand how audio signals are coded when being sent to our brain we could easilly send anything in a manner how we hear things in real world. In that scenario you don't need to use recording microphones, you record neuro signals being transmitted to your brain while you are listeing to the concert in a concert hall (or wherever) and they you simply reproduce those signals when you want to play it again.

 

[Krunok]

That's one of the strengths of Sonarworks- it's all automated. And IME, just about foolproof.

But it's set of pre-made EQ settings for certain models of headphones and not for speakers, right?

 

[RayDunzl]

My microphone is calibrated and cal file is loaded into REW, but I don't know how to calibrate SPL level in REW.

If the calibration file is working and properly formatted, it should display a fairly accurate SPL with no further intervention.

Play a tone and watch the level in the RTA window. Then...

Adjust the microphone level...

And the level reported in the RTA (live, not peak - existing peak won't adjust), and the SPL Meter, and wherever else, will remain the same as REW adjusts itself.

---

Example:

Drop input volume (gives more headroom) - see the DBFS in the SPL meter, but SPL remains (about) the same.

If it doesn't, the calibration file isn't working, and the SPL displayed may or may not be reasonable.

 

[FrantzM]

I dont agree. If we would be able to understand how audio signals are coded when being sent to our brain we could easily send anything in a manner how we hear things in real world. In that scenario you don't need to use recording microphones, you record neuro signals being transmitted to your brain while you are listening to the concert in a concert hall (or wherever) and they you simply reproduce those signals when you want to play it again.

We are speculating .. allow me to offer some counterarguments ...

Your assuming that the proces is linear and that the path from auditory stimuli to the brain doesn't undergo any processing or alterations.. Other psychological process may interfere with this transmission, for example how you are feeling at the moment or even your appreciation of the music ... or genres ...or ... You can see where I am going with that ...

 

[Frank Dernie]

I would imagine there would ne no compression if that driver is a tweeter but if it is a bass driver delivering 90dB of SPL I would imagine there would be some air compression, probably significant..

Compressibility effects come into effect above Mach 1.
This is a bit like the idea that having a rigid link between bearing and headshell on a record player being important, seems plausible but is actually not supported by the science...

 

[Krunok]

If the calibration file is working and properly formatted, it should display a fairly accurate SPL with no further intervention.

Play a tone and watch the level in the RTA window. Then...

Adjust the microphone level...

And the level reported in the RTA (live, not peak - existing peak won't adjust), and the SPL Meter, and wherever else, will remain the same as REW adjusts itself.

---

Example:

View attachment 19611

Drop input volume (gives more headroom) - see the DBFS in the SPL meter, but SPL remains (about) the same.

View attachment 19612

If it doesn't, the calibration file isn't working, and the SPL displayed may or may not be reasonable.

Thank you Ray, I'll give it a try. What I can't understand is why I'm getting different levels when measuring with RTA vs when I do log sine sweep although volume on my Volumio player is set to the same value.

This is how calibration file looks:

*1000Hz -39.3

20.00 -2.4
20.55 -2.3
21.11 -2.3
21.69 -2.3
22.29 -2.2
22.90 -2.2
23.53 -2.1
24.18 -2.0
24.84 -1.9
25.52 -1.9
26.22 -1.8
26.94 -1.7
27.68 -1.6
28.44 -1.5
29.22 -1.4
30.03 -1.4
30.85 -1.3
31.70 -1.3
32.57 -1.2
33.46 -1.2
34.38 -1.2
35.33 -1.1
36.30 -1.1
37.29 -1.1
38.32 -1.1
...
18438.94 -1.9
18945.26 0.0
19465.49 0.5
20000.00 0.2

REW loaded it without any problems.

 

[Krunok]

We are speculating .. allow me to offer some counterarguments ...

Your assuming that the proces is linear and that the path from auditory stimuli to the brain doesn't undergo any processing or alterations.. Other psychological process may interfere with this transmission, for example how you are feeling at the moment or even your appreciation of the music ... or genres ...or ... You can see where I am going with that ...

Sure, I do. But that is acceptible as that is how our brain works anyway. We don't always have the same reaction to the same stimuli, but that is a feature, not a bug.

 

[Krunok]

Compressibility effects come into effect above Mach 1.
This is a bit like the idea that having a rigid link between bearing and headshell on a record player being important, seems plausible but is actually not supported by the science...

Aaa, ok I see, thank you!

 

[Krunok]

If the calibration file is working and properly formatted, it should display a fairly accurate SPL with no further intervention.

Play a tone and watch the level in the RTA window. Then...

Adjust the microphone level...

And the level reported in the RTA (live, not peak - existing peak won't adjust), and the SPL Meter, and wherever else, will remain the same as REW adjusts itself.

Btw, as I'm using Volumio I can't play a tone via REW, I can only generate a file fia REW (like shown below) and play it.

 

[RayDunzl]

Play the tone whereever (in the air) , check the REW SPL level, change the microphone volume level in Preferences, see if REW adjusts itself to maintain the same SPL reading.

If it does, you're probably "calibrated". If not, ???

 

[SIY]

But it's set of pre-made EQ settings for certain models of headphones and not for speakers, right?

No, it does full in-room EQ of speakers. There's a headphone module in it (which basically comprises their True-Fi headphone EQ software), but the main software runs you through an automated room EQ process. Once that's done, you can set it up either as a VST plug-in or as "Systemwide." AX was nice enough to put my review online.

 

[Krunok]

Play the tone whereever (in the air) , check the REW SPL level, change the microphone volume level in Preferences, see if REW adjusts itself to maintain the same SPL reading.

If it does, you're probably "calibrated". If not, ???

Ok, it's calibrated now. As I can connect my mic to my phone I downloaded SPL meter app and calibrated REW using external calibration value from the SPL meter app.

This is what I'm getting now with RTA when playing 420Hz tone:



That peak level is the same as reported by SPL meter when using the same mic from the same position.

And this is for 4000Hz tone:



This is at app 62dB so THD figures are decent, but I can't crank it up now as my neighbours have already started giving me "the look" when we meet in the yard.

 

[Cosmik]

I dont agree. If we would be able to understand how audio signals are coded when being sent to our brain we could easilly send anything in a manner how we hear things in real world. In that scenario you don't need to use recording microphones, you record neuro signals being transmitted to your brain while you are listeing to the concert in a concert hall (or wherever) and they you simply reproduce those signals when you want to play it again.

With your method, you are still only experiencing the audio from one point in space - even if the point moved about at the concert. When you are playing it back, it is as though you are moving about in the same way as the person whose brain waves were being recorded at the concert (check out the film Brainstorm). Maybe that's good if you can re-live everything including the 'motivations' of the person at the gig, but it isn't the same as you, now, being at the gig. It probably involves you sitting in a chair with a special headset on and alarms that go off to remind you to go to the toilet.

The alternatives we have now are:

1. Headphones that give the same audio as being at a gig - if recorded using a binaural dummy head, at least. But you can't move about at will in the concert. There's no physical sensation of acoustic power.
2. Speakers that create a hybrid between being at the gig and being in your house. You can even move around and turn your head to a limited extent. You can feel the acoustic power. It contains the essence of a real concert even if it's not a perfect facsimile.
3. Synthesised acoustics (and visuals) with head tracking. It doesn't tap directly into your brain, but it aims to reproduce the same experience as you, now, being at a virtual concert and able to move around. Depending how detailed the model, it could be a fair representation of what you would hear (and see) at a real concert. You could even experience it with other people who are physically located all over the world.

I think they're all fascinating, but (2) is the one everyone will ultimately live with the most happily - just as most people prefer to watch 2D TV, with their 3D goggles gathering dust.

 

[Krunok]

With your method, you are still only experiencing the audio from one point in space - even if the point moved about at the concert.

Well you can't experience audio from some other point in space different than the one where you are, can you?

The point is to experience audio in the very same quality as you are being there and current technology with microphones and loudspeakers can't give you that.

P.S. I'm more thinking "augmented reality", not "virtual reality", so no problem with going to toilet.

 

[FrantzM]

Sure, I do. But that is acceptible as that is how our brain works anyway. We don't always have the same reaction to the same stimuli, but that is a feature, not a bug.

True that! By then , there will be "an app for that"

 

[Krunok]

@RayDunzl , how do you clear measurement in RTA window?
When I press Reset averaging it doesn't clear the window so I found a workaround but I suspect there is more elegant way to do it.

@JohnPM , do you have an idea why log sine sweep measreuments show app 9db higher than RTA?
Also, can you please help with clearing the RTA window question?

 

[JohnPM]

To remove the display of the currently selected measurement just untick the check box for it in the legend. These kinds of questions probably belong in one of the dedicated REW forums though.