"The phase coherence of harmonics in the vocal formant range, ~630Hz to 4000Hz" - Page 11 - diyAudio
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Multi-Way Conventional loudspeakers with crossovers

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Old 30th November 2012, 06:35 PM   #101
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Binaural demo of ambiophonics. - YouTube
This is a binaural demo of ambiophonics.
Don't judge on sound quality. it's highly compressed (youtube) and I used a Kodak playtouch pocket recorder.

Notice the depth of field and how the center image is the same size as the R+L.

One guitar should be far left and one guitar should be just right of center.

Of course, this all depends on your own HRTF, I used my own head and ears for the recording.

Also, there are no treatments in this room, so it will sound a little wet to you, but perfectly natural to me because I'm used to my room signature.

Notice the airplane that comes in at 1:00.... that's in the recording, and sounds like a real airplane overhead in my room.

Notice how the cereal sound pans from R to C at 1:35....The HF certainly gets crisper due to correct pinna cues. This is the fault of the prototype speaker. I placed the R+L drivers way to close, 10" apart. This is something that will be remedied in my current build.....The "Supernova" found under the full range forum.
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Old 30th November 2012, 07:03 PM   #102
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Hi Tom,

What is phase coherence of speaker at one meter? What does 120Hz square wave look like? And at 5 degrees off axis horizontally, vertically and both?

Regards,

Andrew

Last edited by Barleywater; 30th November 2012 at 07:05 PM. Reason: detail
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Old 30th November 2012, 07:42 PM   #103
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Hi Barleywater

If by “phase coherence” you mean the acoustic phase as shown, it is the phase relationship between the input signal and the acoustic pressure the speaker produces. To get acoustic phase (per Heyser) you need to remove the apparent phase added due to the time of flight between the speaker and microphone. What is left when you remove all of the fixed delay is the acoustic phase of the source itself, that acoustic phase and the amplitude response govern how well a loudspeaker can reproduce the waveshape of a complex input signal, like a square wave or say music.

Fwiw, the SH-50 only reproduces a square wave from about 240Hz to 2900 Hz, it does so anywhere from very good looking on oscilloscope to fair depending. Over a broad band, the speaker radiates a portion of a sphere about 50 by 50 degrees.
There is very little change in appearance of the square wave until one is nearing the pattern edges, there radiate as if there had only one driver so there aren’t any lobes or nulls at crossover or anywhere else, just one forward lobe.
It does this because anywhere two or more drivers / sound sources interact; they are less than a quarter wavelength apart and so add coherently.
An odd ball crossover and the front to back spacing allows the elimination of the phase shift (time off set) the “named” crossover slopes impose resulting in one source in time as well as space, over a broad band..

This is the design approach essentially all of our full range loudspeakers use, the SH-50 and these being one of our oldest products.

Here are more based on the same acoustic approach;

Danley Loudspeakers | Danley Sounds Labs | Danley Sound Labs, Inc.

http://www.facebook.com/DanleySoundLabs?ref=ts

While a standard, perhaps what matters more than the response at one meter is the mag and time response at the listening position where you are when you experience the loudspeaker.
Best,
Tom Danley
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Old 30th November 2012, 08:02 PM   #104
ScottG is offline ScottG  United States
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Originally Posted by markus76 View Post
Scott,

I can only speculate what's causing the difference in perception. My front wall is completely covered with absorption and speakers have high directivity (though there's no absorption at side walls and speakers are not toed-in). So it's probably the difference in the indirect sound field of our rooms.

Would love to hear other's results. Here's the link again:
https://dl.dropbox.com/u/21936387/au...onic_highs.zip
Yes, it is interesting.

..The minor differences could be down to reflections, though again, when I tested them the second time it was well away from walls.

As for the L channel discrepancy vs. the R - that could be a problem with my sound driver (or something else).

Anyway - it's was enjoyable and I'm glad Tom took the time to try it out and comment.
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Old 30th November 2012, 09:36 PM   #105
Rudolf is online now Rudolf  Germany
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Tom.wav is clearly more focussed than 1 or 2.5 - with no real difference between 1 and 2.5 for me. I can't comment on depth, since 1 and 2.5 sound a bit duller than Tom.wav. That could suggest more distance.

One personal peculiarity to speak of: Tom.wav travels at (somewhat) equal angles from left to right. But in 1 and 2.5 the central "tom" and the next two "toms" to the right form a sort of cluster with reduced angles between them and a large angle to the third "tom" from center.

My right ear canal is kind of "un-normal", since no standard earplugs or earbuds keep hold in it. I reckon that 1 and 2.5 lack some information, that stabilizes the angular separation in tom.wav - at least for me.

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Old 30th November 2012, 09:47 PM   #106
ScottG is offline ScottG  United States
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Attachment 314878



My right ear canal is kind of "un-normal", since no standard earplugs or earbuds keep hold in it. I reckon that 1 and 2.5 lack some information, that stabilizes the angular separation in tom.wav - at least for me.

..makes me think I need to have my hearing checked - it's always a possibility that something is wrong there.
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Old 1st December 2012, 03:34 AM   #107
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Originally Posted by Tom Danley View Post
Hi Barleywater

If by “phase coherence” you mean the acoustic phase as shown, it is the phase relationship between the input signal and the acoustic pressure the speaker produces. To get acoustic phase (per Heyser) you need to remove the apparent phase added due to the time of flight between the speaker and microphone. What is left when you remove all of the fixed delay is the acoustic phase of the source itself, that acoustic phase and the amplitude response govern how well a loudspeaker can reproduce the waveshape of a complex input signal, like a square wave or say music.

Fwiw, the SH-50 only reproduces a square wave from about 240Hz to 2900 Hz, it does so anywhere from very good looking on oscilloscope to fair depending. Over a broad band, the speaker radiates a portion of a sphere about 50 by 50 degrees.
There is very little change in appearance of the square wave until one is nearing the pattern edges, there radiate as if there had only one driver so there aren’t any lobes or nulls at crossover or anywhere else, just one forward lobe.
It does this because anywhere two or more drivers / sound sources interact; they are less than a quarter wavelength apart and so add coherently.
An odd ball crossover and the front to back spacing allows the elimination of the phase shift (time off set) the “named” crossover slopes impose resulting in one source in time as well as space, over a broad band..

This is the design approach essentially all of our full range loudspeakers use, the SH-50 and these being one of our oldest products.

Here are more based on the same acoustic approach;

Danley Loudspeakers | Danley Sounds Labs | Danley Sound Labs, Inc.

http://www.facebook.com/DanleySoundLabs?ref=ts

While a standard, perhaps what matters more than the response at one meter is the mag and time response at the listening position where you are when you experience the loudspeaker.
Best,
Tom Danley

By phase coherence I am referring to phase and magnitude of frequency components of signal being maintained in output. Square wave is convenient example even with band limiting imposed by sampling rate.

The direct sound waveform received at listener position will correlate highly with output of speaker along design axis for smoothly produced wavefront. This is basis for how mind sees rest of room with ears.

Picture is worth a thousand words; frequency response, phase plot, and knowledge of minimum phase all pass at 300Hz and 1200Hz precludes stable square wave across most of operating band.

Attached is zip of swept square wave from about 100Hz to 3kHz captured on design axis of DSP implemented Pluto type speaker over 10 seconds. File is intended to look at with editor in lieu of numerous pics.

Diffraction as off axis frequency/angle dependent radiation leads to splotchy illumination consistent across source material, leading to identifiable sameness imparted to listening experience of system/space.

Similarly, baffle edges, sound reflecting off magnets and baskets, along with insides of cabinets that comes back through driver(s) impact resolution of system and identity as projector.

The panning experiments with modified bandwidth and uncluttered sound field reveal classic difficulties in achieving repeatable reference monitoring regarding sound image.

Regards,

Andrew
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Old 1st December 2012, 09:41 AM   #108
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Quote:
Originally Posted by Barleywater View Post
The direct sound waveform received at listener position will correlate highly with output of speaker along design axis for smoothly produced wavefront.


Quote:
Originally Posted by Elias View Post
It's all nice, BUT, what will happen to the harmonic phase coherence when you put 2 loudspeakers in a triangle and get terrible stereophonic comb filtering at the listening position ?
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Old 1st December 2012, 10:04 AM   #109
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Old 1st December 2012, 10:13 AM   #110
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There should be at least one possible solution to reproduce sound over loudspeakers while the above requirements remain achievable: Cross talk cancelling
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