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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 23rd April 2016, 09:02 AM   #241
wesayso is offline wesayso  Netherlands
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The mid/side EQ would be easier with some plugins I guess. I'm using Voxengo's mid-side plugin as shown earlier in this thread, like this:
Click the image to open in full size.
But with EQ on the other leg as well. The biggest challenge was to adjust tonality to counter the change in overall tonal balance. Something that Pano mentioned being necessary for the Phase Shuffler as well.

I do agree with your results and perception. They mimic my experience. I'm glad you took the test. We could have talked about it for ages but hearing it is much more powerful.

I might even go back and give that last Rephase 2 shuffler another shot. Last time I tried I had to convolve songs off line to get to hear it. But it should be possible to run 2 convolutions, I need the first one for my base EQ/time alignment.

Fun stuff, isn't it?
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Old 23rd April 2016, 05:45 PM   #242
dynomike is offline dynomike  Canada
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Yeah, I figured that was how it was set up. That Voxengo plugin sure is useful. Could we see what the EQ is that you have on the side channel vs mid channel?

As I listen to it more, the "rephase-2" phase-only shuffler is just incredible. It tightens up the imaging of mono (center) material so much. I don't hear too much talk about mono imaging too much, because it usually sucks I guess. Has real depth now!

Pano do you have the settings file for Rephase? I wanted to load it up and make some IRs at other sample rates. And experiment with it a bit, but having a known starting point. I may just try to recreate it from the image you posted.
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Old 23rd April 2016, 08:21 PM   #243
dynomike is offline dynomike  Canada
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Similar effects on the Infinity tower speakers (out from walls, 1.3m equilateral triangle).

Tightens up center image at times an uncomfortable amount... ie. hip hop with a lot of extremely dry center elements (dead vocal booth, direct drum machine..). When mixes actually rely on the fuzziness of the phantom center to give center elements greater ASW (apparent source width), it can eat up some of the magic. I still prefer it pretty much all the time, even when the extra transparency reveals "the man behind the curtain"...
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Old 23rd April 2016, 10:25 PM   #244
wesayso is offline wesayso  Netherlands
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The mid/side EQ I used to judge was something like this:

Side signal: boost at 400 Hz, Q = 0.5 Gain = 1 dB, cut at 4000 Hz, Q = 0.4 Gain = -1 dB
Mid signal: cut at 400 Hz, Q = 0.5 Gain = -1 dB, Boost at 4000 Hz, Q = 0.4 Gain = 1 dB

This was used to listen to center and side vocals for tonal balance. After that I have made changes to the overall balance so it has changed but it would not make much sense to post it separate from the rest of the things I do. Which include ambient channels where I have an opposing cut at 400 Hz in the side channels for example.

I compared this to the first shuffler presented in this thread. I still need to revisit that last rephrase shuffler. What I did notice in the brief test I did on that one that it was a big improvement compared to the first one presented in this thread. Meanwhile I moved on to the ambient experiments. That alone can create it's own troubles with tonal changes. So I never gave the second shuffler a fair chance. But I haven't forgotten it and will pick it up at some point.

I'm glad you're liking the results. I'm thinking the mid/side EQ might not give the same benefit with more traditional speakers. The way I see it line arrays already have a lot of tiny phase shifts due to the use of multiple drivers. But it can't hurt to try.

I do have some extra cuts at 3700 Hz and 7270 Hz in the mid signal (very specific to my speaker/listening distances) after some cross talk cancelation experiments. It loosely relates to the dips created by introducing an opposing signal in each channel with a delay of 0.270 ms. (difference between the ears at the listening spot) This improved the intelligibility of some specific material.

Last edited by wesayso; 23rd April 2016 at 10:28 PM.
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Old 23rd April 2016, 10:59 PM   #245
Pano is offline Pano  United States
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Fixing the Stereo Phantom Center
Hi Mike and thanks for trying it and posting your results. Stereo is a wonderful illusion, but it isn't perfect, especially for the phantom center. This shuffler seems a good way of fixing some of those problems.

The 2nd of the phase only shuffler files should, in theory, be the best. So far it has been found to be so in the very limited number of test we have made. I'll dig to see if I can find the settings file, not sure if I saved it. Hadn't thought about adding EQ or other effects to it, that's a good idea.

As for EQing the system after the shuffle, it will probably be individualized. Since the comb filtering is different for different head sizes and shapes, what the shuffler does will be different for different heads. That said, a good comprise could probably be reached.
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Old 23rd April 2016, 11:10 PM   #246
Bob Richards is offline Bob Richards  United States
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In the case of a 3 speaker arrangement (like I'm building), whatever else I do with delays, I would want the center speaker acoustic signal to arrive first, so precedence effect would put it out front of the rest of the band.

What I was getting at in a previous comment was that using a very short delay (1 - 20mS) to create a decorrelation between the center and the L&R side spkrs. would also create comb filter effects due to crosstalk in the extraction process (L+R center and L-XR/R-XL for sides, X being continuously variable so can be better optimized). But if instead of a single delay, several delays were used in that time range (1 - 20mS), and they had either a 1.4 or 1.62 delay relation to each other, and with the other channel(s), then maybe the cancellations would get largely filled in with minimal doubling up of cancellations and/or their integral multiples. Much like how listening room acoustics work, where the worse case is one reflection, and many reflections largely fill in each others cancellations, leaving you with something listenable.

This technique may be able to work with only two speakers too, to improve the phantom center image apparent stability when a bit off axis. You'd pull the L+R away from the L and R (with the above mentioned stereo matrix and L+R), add the delays to each of the 3 signals strategically as mentioned above, and then re-combine them somehow... Or, you might want to just add the multiple delays to the center image, and only a single slightly longer delay (~16mS) to the L and R signals, so the center image would stay out front (precedence effect). 'coarse I could be wrong... (?) My understanding of decorrelation is that it creates more of a sense of separateness from other signals. I haven't found a detailed explanation as to how it's done in the real world (in stereo output digital reverbs for ex.), but I'm guessing it's about using multiple delays too short to perceive, but long enough to do the job (?)..
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Old 24th April 2016, 02:32 AM   #247
BYRTT is offline BYRTT  Denmark
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Fixing the Stereo Phantom Center
Quote:
Originally Posted by dynomike View Post
.....Pano do you have the settings file for Rephase? .....
Quote:
Originally Posted by Pano View Post
.....I'll dig to see if I can find the settings file, not sure if I saved it......

Settings file for Rephase attached below and it is created visual by comparing to Pano's posted graph, after that tried wav-file import to REW and exported as frd-file for import into Rephase to flatten phase and that way find numbers but result didn't get any closer than first try.
Attached Images
File Type: png 91.png (24.0 KB, 124 views)
Attached Files
File Type: zip rephase_shuffle-2_PANO.zip (1.2 KB, 29 views)
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Old 24th April 2016, 03:20 AM   #248
dynomike is offline dynomike  Canada
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Quote:
Originally Posted by BYRTT View Post
Settings file for Rephase attached below and it is created visual by comparing to Pano's posted graph, after that tried wav-file import to REW and exported as frd-file for import into Rephase to flatten phase and that way find numbers but result didn't get any closer than first try.
Nice, thanks. I ended up doing the Wav -> REW -> txt -> rePhase method myself, but couldn't figure out how to get 2 channels showing at once in rePhase...

How did Pano come up with those "shuffle frequencies" anyway? They seem related to the ear-spacing comb filter frequencies?
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Old 24th April 2016, 04:23 AM   #249
BYRTT is offline BYRTT  Denmark
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Fixing the Stereo Phantom Center
Quote:
Originally Posted by dynomike View Post
Nice, thanks. I ended up doing the Wav -> REW -> txt -> rePhase method myself, but couldn't figure out how to get 2 channels showing at once in rePhase.....
To cheat and get Rephase visual show 2 channels load the settings file and hit "Generate" button which make blue trace in plot go red and into memory, now at "General" tab invert time and you will see new actual settings as blue trace together the remembered red trace.

Can think of generate one separate mono or stereo IR-wav file for above non inverted and inverted correction one at a time and then let a config-file for JRiver point to left and right IR-wav file. But how Pano did create one stereo IR-wav file that have non inverted and inverted correction for left and right in one stereo IR-wav file i don't know, can only guess that maybe Audacity can create that mix.

Quote:
Originally Posted by dynomike View Post
.....How did Pano come up with those "shuffle frequencies" anyway? They seem related to the ear-spacing comb filter frequencies?
i'm blank that subject : ) but can easy hear his IR-wav file creation works.
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Old 24th April 2016, 09:07 AM   #250
wesayso is offline wesayso  Netherlands
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Quote:
Originally Posted by Bob Richards View Post
In the case of a 3 speaker arrangement (like I'm building), whatever else I do with delays, I would want the center speaker acoustic signal to arrive first, so precedence effect would put it out front of the rest of the band.

What I was getting at in a previous comment was that using a very short delay (1 - 20mS) to create a decorrelation between the center and the L&R side spkrs. would also create comb filter effects due to crosstalk in the extraction process (L+R center and L-XR/R-XL for sides, X being continuously variable so can be better optimized). But if instead of a single delay, several delays were used in that time range (1 - 20mS), and they had either a 1.4 or 1.62 delay relation to each other, and with the other channel(s), then maybe the cancellations would get largely filled in with minimal doubling up of cancellations and/or their integral multiples. Much like how listening room acoustics work, where the worse case is one reflection, and many reflections largely fill in each others cancellations, leaving you with something listenable.

This technique may be able to work with only two speakers too, to improve the phantom center image apparent stability when a bit off axis. You'd pull the L+R away from the L and R (with the above mentioned stereo matrix and L+R), add the delays to each of the 3 signals strategically as mentioned above, and then re-combine them somehow... Or, you might want to just add the multiple delays to the center image, and only a single slightly longer delay (~16mS) to the L and R signals, so the center image would stay out front (precedence effect). 'coarse I could be wrong... (?) My understanding of decorrelation is that it creates more of a sense of separateness from other signals. I haven't found a detailed explanation as to how it's done in the real world (in stereo output digital reverbs for ex.), but I'm guessing it's about using multiple delays too short to perceive, but long enough to do the job (?)..
While obviously I didn't play with a 3 speaker setup close together I did play with delaying the sides compared to the center. What I ended up with were strange effects and 3 sources. Left, Right and Center... no real imaging in between. It was fun to play with, but it didn't impress . I only tried very short delays.

I can see the cross talk cancelation working with such a setup though. I never got that to work properly with a stereo pair of speakers. At least not for the complete stereo field. I tried several variants of available plugins and convolution files. Mess with the stereo mix too much and you end up with only 3 mayor sources of sound.

I'd like to try that last shuffler again with a slight EQ at ~400 Hz to the sides.
I'm in no hurry though as I do enjoy what I've got right now. The ambient addition was one of my most successful experiments, besides cleaning up the early waterfall plots with various measures. The biggest of those measures being time coherency.
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