# Soundcard Calibration Help



## Phillips (Aug 12, 2011)

Hi 

I have moved REW on to another laptop.

I am trying to do a sound card calibration file for the other laptop. 

I have attached some print/screen shots of the settings, please can you advise.

It has a single in and out.

Looking last night there was stereo mix and mono mix as well (hidden in the advanced settings)

The laptop is XP and about 8-10 years old. 

I tried to download the Realtek High Definition Drivers (but came back with Audio may not start code 10), or something better currently using ALi, old? Any ideas please?

The general error i get is "Excess Variation" 

Help would be really appreciated?

Thanks in advance

View attachment Laptop Settings.zip


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## robbo266317 (Sep 22, 2008)

You may want to look in the REW FAQ section as laptop soundcards are not ideal (ie not supported)


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## Phillips (Aug 12, 2011)

robbo266317 said:


> You may want to look in the REW FAQ section as laptop soundcards are not ideal (ie not supported)


Thanks for that, i got good results on the other laptop. 

Thanks again


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## JohnM (Apr 11, 2006)

Some pointers on the settings you posted: On the output side you had everything muted (except Line In, but with master volume muted there would still be no output). What you should have is everything muted *except* Master Volume and Wave. That set of controls affect what comes out of your laptop, the only thing you want coming out is REW's Wave signal. Line in must be muted on that output control, otherwise you have a feedback loop. On the Recording settings you had microphone selected instead of Line In, you should select Line In.


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## Phillips (Aug 12, 2011)

JohnM said:


> Some pointers on the settings you posted: On the output side you had everything muted (except Line In, but with master volume muted there would still be no output). What you should have is everything muted *except* Master Volume and Wave. That set of controls affect what comes out of your laptop, the only thing you want coming out is REW's Wave signal. Line in must be muted on that output control, otherwise you have a feedback loop. On the Recording settings you had microphone selected instead of Line In, you should select Line In.



Hi John thanks for your reply.

I have attached two files, mdat, Word with the results, still not working.

Maybe it is the cabling i am using?

Thanks again

View attachment Soundcard Trial.zip


View attachment Soundcard.pdf


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## JohnM (Apr 11, 2006)

Make sure you are actually generating output first, connect the soundcard output to an input on your receiver and check that signals are getting through OK - use the REW signal generator or simply run a measurement and listen to the result. Also double check which connectors on the soundcard you are plugged into.


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## Phillips (Aug 12, 2011)

JohnM said:


> Make sure you are actually generating output first, connect the soundcard output to an input on your receiver and check that signals are getting through OK - use the REW signal generator or simply run a measurement and listen to the result. Also double check which connectors on the soundcard you are plugged into.



Hi John thank you

I have attached measurements and settings that were set for the measurement.

I had to untick the "PCM Out" to get any output.

There was noticeable noise through the speakers, i tapped the mic but nothing came through the speakers that i could hear.

The "Output Device and Output" and "Input Device and Input" are highlighted ( 4 tabs) have i selected the correct ones?

Thanks again 

View attachment Measurements Settings.zip


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## JohnM (Apr 11, 2006)

That is a valid measurement, so setup is OK. I see you are now using Omnimic as the input. A couple of things remaining, the levels are plotting a little low, may need to redo the REW SPL Calibration to correct them. Also the distortion is high, especially the odd harmonics. That can be caused by clipping somewhere, was the measurement quite loud? May need to turn down the output level from your laptop and turn up the volume on your receiver to compensate, in case the receiver input is being overloaded. There is also an inversion somewhere in the signal chain, that only affects phase results but you can correct it by ticking the 'Invert' box under Input Options on REW's soundcard preferences.


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## Phillips (Aug 12, 2011)

JohnM said:


> That is a valid measurement, so setup is OK. I see you are now using Omnimic as the input. A couple of things remaining, the levels are plotting a little low, may need to redo the REW SPL Calibration to correct them. Also the distortion is high, especially the odd harmonics. That can be caused by clipping somewhere, was the measurement quite loud? May need to turn down the output level from your laptop and turn up the volume on your receiver to compensate, in case the receiver input is being overloaded. There is also an inversion somewhere in the signal chain, that only affects phase results but you can correct it by ticking the 'Invert' box under Input Options on REW's soundcard preferences.


Thanks John.

By using the Omnimic input seem to improve the headroom slightly, should i change it back, which should i select?

No the measurement was not loud.

Is there any other print screen shots you would like me to send.

Shall i go ahead and do the sound card measurement with the present laptop settings etc?

Thanks again


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## JohnM (Apr 11, 2006)

It is OK to use the Omnimic for measurement, but you can't make a soundcard loopback with it - that would have to use the soundcard line in.


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## Phillips (Aug 12, 2011)

JohnM said:


> It is OK to use the Omnimic for measurement, but you can't make a soundcard loopback with it - that would have to use the soundcard line in.


Hi John i have attached a Sound Card measurement from my *previous laptop* that only had Headphones out and Mic In.

Sorry i am a little confused, i thought if i was able to do a sound card measurement that it would be ok to enter in to "preferences" "soundcard" "calibration" "file" so REW can allow for the soundcard measurement and i miss out having timing reference. 

Does this look ok?

View attachment Soundcard.zip


Thanks again


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## Phillips (Aug 12, 2011)

Hi John i have attached all the settings available for the laptop "sound", also whats available with the outputs & inputs for REW with all the cables in place, like ready to measure.

BTW I did some more measurements today and found that the noise is when the mains power, as soon as i run on battery the noise goes away. Is there any way i can run on mains power without the noise?

View attachment Laptop Sound Card Settings.zip



Thanks again


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## JohnM (Apr 11, 2006)

Phillips said:


> BTW I did some more measurements today and found that the noise is when the mains power, as soon as i run on battery the noise goes away. Is there any way i can run on mains power without the noise?


Probably not. It might be noise from the power supply (some generate a lot of electrical noise) or there may be a big ground loop through the power supply and the soundcard cabling to your receiver, either way running on battery is the easiest solution.

On the soundcard settings, I don't know what question you are asking. If you want to make a loopback measurement of the soundcard, you need to have the soundcard selected as the output *and *the input, and a cable connected from the soundcard output back to the soundcard line input. You can't measure the soundcard if the input is set to be the Omnimic.


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## Phillips (Aug 12, 2011)

JohnM said:


> Probably not. It might be noise from the power supply (some generate a lot of electrical noise) or there may be a big ground loop through the power supply and the soundcard cabling to your receiver, either way running on battery is the easiest solution.
> 
> On the soundcard settings, I don't know what question you are asking. If you want to make a loopback measurement of the soundcard, you need to have the soundcard selected as the output *and *the input, and a cable connected from the soundcard output back to the soundcard line input. You can't measure the soundcard if the input is set to be the Omnimic.



Thanks John, would the noise effect the measurements?

I am getting confused with all the settings, and wanting to do a sound card measurement for correction. 

This computer has alot more settings than the other laptop. I was giving all the settings to see if there was anything hiding in there.

I have tried the Ali output and Ali input.

I keep getting the Variation is too great and too low message. I turn up the volume with no success.

Does it matter if the 3.5mm are stereo or mono?

The Omnimic input only appears when the mic is plugged in, but i don't have it plugged in when i am doing soundcard measurement.


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## JohnM (Apr 11, 2006)

3.5mm soundcard sockets are stereo, so you would need to use stereo jacks in them.


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## Phillips (Aug 12, 2011)

Hi John i have attached a mdat file with a REW measurement + Imported Omni Wav file 32 bit and a imported Omni software FRD file, all labelled. I am aware of the smoothing difference.

These were made from the other laptop, i thought before transferring to another laptop it would pay to make sure the mic / system is compatible / working.

All measurements were taken with the same mic / position, just different software.

Please could you look at these, very interesting, the REW + Omni Wav files look similar.

The Omnimic is generic.

I have seen something about response correction/calibration and not having sample clocks locked. Would this make a difference?

Thanks in advance

View attachment REW Comparison.zip


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## JohnM (Apr 11, 2006)

The Omnimic wav and REW measurement do show very good agreement, although the REW measurement has better S/N (by about 13dB).


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## Phillips (Aug 12, 2011)

JohnM said:


> The Omnimic wav and REW measurement do show very good agreement, although the REW measurement has better S/N (by about 13dB).


Thanks John

Please can you explain why the frequency response graph looks so different between the REW and Omni FRD measurement? The Omnimic Imported Wav files (2) and Omnimic FRD file relate to each other. I realize the smoothing is different.

Would the response correction/calibration and not having sample clocks locked. Would this make a difference?

Thanks in advance


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## JohnM (Apr 11, 2006)

The FRD file is similar at low frequencies if you apply 1/12th octave smoothing to the REW measurement, though the FRD seems to be more heavily smoothed as frequency increases. Difficult to know quite what is being done to produce the frd result, but the underlying impulse response looks the same as REW's, based on the imported wav files.


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## Phillips (Aug 12, 2011)

JohnM said:


> The FRD file is similar at low frequencies if you apply 1/12th octave smoothing to the REW measurement, though the FRD seems to be more heavily smoothed as frequency increases. Difficult to know quite what is being done to produce the frd result, but the underlying impulse response looks the same as REW's, based on the imported wav files.


Hi John thank you

If I look at both the REW measurement and imported FRD file and use 1/1 smoothing (or more) the bass especially looks down with the REW measurement?

Is it the impulse response (REW and Imported Wav file) that counts the most that should line up?

Thanks again


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## Barleywater (Dec 11, 2011)

Comparison of wave file exported from Omnimic software is only route to valid comparison.

Sweep lengths used with Omnimic and REW need to be of same length.

Omnimic results appear to use short sweep. This is evidenced by S/N ratio as pointed to by John. Also seen directly in IR displays. Omnimic soft appears to truncate result at about t=-1ms. Omnimic results have pre-ringing artifact before t=0. This is likely aliasing do to sweep being too short; thus insufficient bandwidth:









The two Omnimic imported waves produce poor repeatability as seen with A/B trace arithmetic:









For good comparison multiple measurements are needed with each software. Omnimic exported waves should not be normalized.

A/B trace arithmetic of repeated measurements should produce exceptionally flat SPL across frequency band of interest.

Resolution/number of data points of Omnimic cal file is relatively low as indicated by smoothness of cal file spl display; and may be biggest source of apparent differences viewed as SPL, due to way Omnimic and REW apply correction data to actual measurements:









Cal data doesn't look much different than average ECM8000 data.

Nonetheless, Omnimic is likely suitable for use with REW and your measurement needs.

Regards,

Andrew


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## Phillips (Aug 12, 2011)

Barleywater said:


> Comparison of wave file exported from Omnimic software is only route to valid comparison.
> 
> Sweep lengths used with Omnimic and REW need to be of same length.
> 
> ...




Hi Andrew thank you very much.

I have attached 2 files "New Measurements" (which has some imported Omnimic Wav files) and due to size some extra separate "Omnimic Wav files". These are all labelled. Please see notes in the REW measurements and others

If there are more you would like me to post, please suggest them.

Yes they are short sine sweeps.

Thanks again

View attachment New Measurments.zip


View attachment Omni Imported Wav Files.zip


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