Can you hear phase distortions on your system?

Key · 8th December 2009, 08:40 PM

Pretty straight forward test idea here. I have two copies of two songs but one of the copies of each song has been run through an unneeded crossover filter and summed back together. Lets keep this one blind. If you feel like it later we can do ABXing with two clearly marked examples.

Example 1 A
zSHARE - Lou Reed - Walk on the Wild Side A.flac
Example 1 B
zSHARE - Lou Reed - Walk on the Wild Side B.flac

Example 2 A
zSHARE - Yusef Lateef - _I Dont Stand_ A Ghost Of A Chance With You A.flac
Example 2 B
zSHARE - Yusef Lateef - _I Dont Stand_ A Ghost Of A Chance With You B.flac

Untouched Phase vs LR24 @ 1.5kHz round 1

vs

Key · 8th December 2009, 10:01 PM

Er those huge things were thumbnails when I posted. Anyway if you really can hear a difference between the files a good way to prove it to yourself and others is to use Foobar2000 and a PC to ABX and generate a report.

Theo404 · 9th December 2009, 12:14 AM

Do you mean its same one (A or B) of both tracks you have modified? Or is it random (could still be the same letter) ?

Key · 9th December 2009, 12:17 AM

It's blind and random. I know which one is which. You can actually verify the filter I used independently but not sure I am telling how right now. But in both examples there is one (either A or B) that has an all pass LR24 applied to it. This is significantly more distortion than the average crossover.

Pano · 9th December 2009, 01:19 AM

Is there an ABX plug in for Foobar? Or just play and report what we hear?

Key · 01:37 AM

Highlight the two tracks> Right click> utilities ABX.

If you don't have it you have to reinstall I think. The option is under the installation customizations.

Tell us what you hear as well.

And of course if you can't hear a difference there is no need to really start the ABX. Sometimes A/Bing can make it easier to hear a difference that is present though Guess my point is if you can't hear the difference still let us know.

Pano · 9th December 2009, 01:22 AM

OK, Thanks. I'll check it out.

zapnspark · 9th December 2009, 02:30 AM

Here are some links to the use of all-pass (phase rotator) filters in broadcasting:

The W3AM Phase Rotating Asymmetry Eliminator!

Allpass paper by W4ENE

http://tinyurl.com/hv2ef

When you listen to broadcast music , the odds are high that it's been passed through a phase rotator.

The following are mono voice WAV sound files. Two very different voices.
One of the channels (L or R) has gone through a 4 pole phase rotator.
The other channel is unmodified.

http://tinyurl.com/mqq2wy

http://tinyurl.com/mo536h

(Note that the phase rotator causes a pseudo-stereo effect when listening on
stereo headphones even though the audio source is monophonic)

There is a possible hitch to ABX testing on these types of files. A phase rotator diminishes the peak to average levels of the audio signal. In casual ABX testing of the above files, a couple of people could distinguish L from R. They both reported that the phase rotated signal was subjectively heard as louder.

Just thought I would throw this information out there for your consideration.

Cheers.

ZAP

Key · 9th December 2009, 03:26 AM

Thanks will take a look and listen.

Davey · 9th December 2009, 03:56 AM

Key,

Your second 1.5khz graph indicates MUCH more phase shift than a LR24 crossover would have. I see quite a few wraps when there should only be one. Confusing.

Cheers,

Dave.

8th December 2009, 08:40 PM	#1
Key diyAudio Member Join Date: Jan 2009	Can you hear phase distortions on your system? Pretty straight forward test idea here. I have two copies of two songs but one of the copies of each song has been run through an unneeded crossover filter and summed back together. Lets keep this one blind. If you feel like it later we can do ABXing with two clearly marked examples. Example 1 A zSHARE - Lou Reed - Walk on the Wild Side A.flac Example 1 B zSHARE - Lou Reed - Walk on the Wild Side B.flac Example 2 A zSHARE - Yusef Lateef - _I Dont Stand_ A Ghost Of A Chance With You A.flac Example 2 B zSHARE - Yusef Lateef - _I Dont Stand_ A Ghost Of A Chance With You B.flac Untouched Phase vs LR24 @ 1.5kHz round 1 vs

9th December 2009, 01:20 AM	#6
Key diyAudio Member Join Date: Jan 2009	Highlight the two tracks> Right click> utilities ABX. If you don't have it you have to reinstall I think. The option is under the installation customizations. Tell us what you hear as well. And of course if you can't hear a difference there is no need to really start the ABX. Sometimes A/Bing can make it easier to hear a difference that is present though Guess my point is if you can't hear the difference still let us know. Last edited by Key; 9th December 2009 at 01:37 AM.

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8th December 2009, 10:01 PM	#2
Key diyAudio Member Join Date: Jan 2009	Er those huge things were thumbnails when I posted. Anyway if you really can hear a difference between the files a good way to prove it to yourself and others is to use Foobar2000 and a PC to ABX and generate a report.

9th December 2009, 12:14 AM	#3
Theo404 diyAudio Member Join Date: Mar 2008	Do you mean its same one (A or B) of both tracks you have modified? Or is it random (could still be the same letter) ?

9th December 2009, 12:17 AM	#4
Key diyAudio Member Join Date: Jan 2009	It's blind and random. I know which one is which. You can actually verify the filter I used independently but not sure I am telling how right now. But in both examples there is one (either A or B) that has an all pass LR24 applied to it. This is significantly more distortion than the average crossover.

9th December 2009, 01:19 AM	#5
Pano diyAudio Moderator Join Date: Oct 2004 Location: SW Florida	Is there an ABX plug in for Foobar? Or just play and report what we hear?

9th December 2009, 01:22 AM	#7
Pano diyAudio Moderator Join Date: Oct 2004 Location: SW Florida	OK, Thanks. I'll check it out.

9th December 2009, 02:30 AM	#8
zapnspark diyAudio Member Join Date: Sep 2006 Location: Midwest	Here are some links to the use of all-pass (phase rotator) filters in broadcasting: The W3AM Phase Rotating Asymmetry Eliminator! Allpass paper by W4ENE http://tinyurl.com/hv2ef When you listen to broadcast music , the odds are high that it's been passed through a phase rotator. The following are mono voice WAV sound files. Two very different voices. One of the channels (L or R) has gone through a 4 pole phase rotator. The other channel is unmodified. http://tinyurl.com/mqq2wy http://tinyurl.com/mo536h (Note that the phase rotator causes a pseudo-stereo effect when listening on stereo headphones even though the audio source is monophonic) There is a possible hitch to ABX testing on these types of files. A phase rotator diminishes the peak to average levels of the audio signal. In casual ABX testing of the above files, a couple of people could distinguish L from R. They both reported that the phase rotated signal was subjectively heard as louder. Just thought I would throw this information out there for your consideration. Cheers. ZAP

9th December 2009, 03:26 AM	#9
Key diyAudio Member Join Date: Jan 2009	Thanks will take a look and listen.

9th December 2009, 03:56 AM	#10
Davey diyAudio Member Join Date: Dec 2001 Location: Bremerton, WA.	Key, Your second 1.5khz graph indicates MUCH more phase shift than a LR24 crossover would have. I see quite a few wraps when there should only be one. Confusing. Cheers, Dave.