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Multi-Way Conventional loudspeakers with crossovers

Fixing the Stereo Phantom Center
Fixing the Stereo Phantom Center
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Old 14th August 2015, 06:05 AM   #91
Kindhornman is offline Kindhornman  United States
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Fixing the Stereo Phantom Center
Pano,
Thanks for the explanation. I didn't zoom in to see that it was only a +/- 30 degree shift, a lot less than some xo's will do on their own really. I do understand the concept, just something new to incorporate into my thinking.
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Old 14th August 2015, 06:26 AM   #92
rastanearian is offline rastanearian  Canada
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Greetings,

I sat down and had a listen to the two counting tracks and found the difference between them to be quite subtle. This was on a pair of Duetta Sigs if that matters any.
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Old 14th August 2015, 06:40 AM   #93
Pano is offline Pano  United States
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Fixing the Stereo Phantom Center
Thanks! Good to know. I suppose not all systems and/or rooms have this tonal shift. But when they do, it's noticeable. For me, once I get a good overall tonal balance, then the sides will seem too bright.
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Old 14th August 2015, 06:47 AM   #94
rastanearian is offline rastanearian  Canada
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Do you find this happens with all your speakers?
I should try it in my other system that uses a more traditional sealed enclosure.
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Old 14th August 2015, 07:09 AM   #95
Pano is offline Pano  United States
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Fixing the Stereo Phantom Center
Not all, no. I'm trying to remember if it occurred with with ESL panels I've used, but can't,
I have heard it in various systems, tho. If it's comb filtering, then it should get worse as phase is more identical between left and right. But maybe it doesn't always.
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Old 14th August 2015, 09:36 PM   #96
Elias is offline Elias  Finland
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Quote:
Originally Posted by Pano View Post
Yes, correct. No center speaker, just the phantom image created between left and right. I have found that the center image has a darker tone than the sides. The paper I linked to early in the thread attempts to explain why this is. The paper proposes comb filtering of the two sources in the center as the cause of the tonality shift. This comb filtering usually causes important nulls at 2K and 6K, thus darkening the tone. That's the simple explanation.

To kill this comb filtering, the phase can be de-corrilated or "shuffled" between the two channels. The plot posted above gives you a good idea of what this looks like. the phase swings up and down +/- 30 degs. Now there is no comb filtering between the two sides. Because them sum to zero, there is no frequency response change to either side, just elimination of the comb filter. That kills the notches and the tonal shift.

Yes, you have to be willing to accept this phase shuffling, normally limited to above 700-900Hz, but so far we are finding that it doesn't damage the image. Oddly enough. It just changes the tone.
I'm trying to get a number of listeners with different systems to tell us what they hear, what they like or don't like about it.

Hi,

I don't see any oddity here, just natural phenomena. Sound localisation above about 1 kHz is dominated by interaural level difference, that is the amplitude difference between the ear signals. Phase loses its importance at high frequencies.

There may be other solutions too. Some say phase randomisation is achieved by bending wave transducers due to their operational principle, without additional phase shifters.

Or if one allows some early room reflections, then cross talk comb notches are filled and become non perceivable. Thus speaker directional patterns becomes important.
One could say highly directional speakers propably benefit more of "phase shuffler" than low directional speakers.


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Old 14th August 2015, 09:40 PM   #97
Elias is offline Elias  Finland
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Quote:
Originally Posted by Pano View Post
This is what the phase shuffle looks like on my latest version. The shuffle part was high passed with a steep filter at 900Hz. Not as smooth looking as I might like, but OK for testing. Basically alternating +/- 30 degs.
Click the image to open in full size.


If you manage to incorporate that phase response included into a passive cross-over, then this method can become very popular


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Old 15th August 2015, 07:05 AM   #98
Pano is offline Pano  United States
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Fixing the Stereo Phantom Center
Quote:
Originally Posted by Elias View Post
Some say phase randomisation is achieved by bending wave transducers due to their operational principle, without additional phase shifters.
That would be interesting to test. Never heard that before.

Quote:
Or if one allows some early room reflections, then cross talk comb notches are filled and become non perceivable. Thus speaker directional patterns becomes important.
One could say highly directional speakers propably benefit more of "phase shuffler" than low directional speakers.
Quite so, yes. Much of this is cover in the white paper.

Quote:
If you manage to incorporate that phase response included into a passive cross-over, then this method can become very popular
Hmmm Tall order. Gotta think about that one.
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Old 20th August 2015, 03:39 AM   #99
Pano is offline Pano  United States
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Fixing the Stereo Phantom Center
POS got me thinning about rePhase so I had a go at making a phase shuffler with it. Made two versions, which you can see below. It's a very different impulse from the original file I did. This affects phase only, not amplitude, as the original shuffler did. Certainly sounds different. The original is a series of quick reflections 11 samples apart that fall off by 5 or 6dB each. The new ones don't work that way at all, it's purely phase manipulation.

If you get a chance, check out the new ones and tell me what you hear.

Also included in the zip file is a perfect impulse. If you run this in your convolver, you should hear no change in the sound at all. If you do, there is something wrong. You can test if convolution is really working by loading the Telephone BW file, you will certainly hear that one if it's working! It is there just to verify that your convolution engine is working. No mistaking the effect if it works.

For those of you who can't use convolution in your playback chain, I will post some files next week that have been preprocessed.

Have fun with the new versions, let me know what you hear, if anything. Cheers!
Attached Images
File Type: png rephase shuffle-1.png (6.7 KB, 290 views)
File Type: png rephase shuffle-2.png (5.5 KB, 289 views)
Attached Files
File Type: zip Shufflers.zip (8.3 KB, 40 views)
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Old 20th August 2015, 03:04 PM   #100
wesayso is offline wesayso  Netherlands
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Briefly listened to the first rephrase shuffler. This one didn't move the position of the sound on the sides for me (that's a good thing). Though it still did seem to push the center image away a bit. I didn't have both tracks (one with convolved shuffler and the original) at the same volume and had to adjust on the fly. They should be exactly the same to form an honest opinion.

I'm testing too many things at once a.t.m. to say anything really useful about the coherency.
I just might have found the improvement I was after in the mid/side processing described in the LoCo link a few pages back. That's still keeping me happy so far and was simple to incorporate because I had all components in place.

I do hope more will listen to this one. If anything I think in my setup the old shuffler was more effective to make a perceivable (positive) change in the tonality of the phantom center. I'll have to give it another go soon.
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