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Old 8th December 2009, 09:40 PM   #1
Key is offline Key  United States
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Default 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

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Old 8th December 2009, 11:01 PM   #2
Key is offline Key  United States
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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.
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Old 9th December 2009, 01:14 AM   #3
Theo404 is offline Theo404  United Kingdom
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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) ?
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Old 9th December 2009, 01:17 AM   #4
Key is offline Key  United States
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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.
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Old 9th December 2009, 02:19 AM   #5
Pano is offline Pano  United States
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Is there an ABX plug in for Foobar? Or just play and report what we hear?
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Old 9th December 2009, 02:20 AM   #6
Key is offline Key  United States
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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 02:37 AM.
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Old 9th December 2009, 02:22 AM   #7
Pano is offline Pano  United States
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OK, Thanks. I'll check it out.
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Old 9th December 2009, 03:30 AM   #8
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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
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Old 9th December 2009, 04:26 AM   #9
Key is offline Key  United States
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Thanks will take a look and listen.
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Old 9th December 2009, 04:56 AM   #10
Davey is offline Davey  United States
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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.
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