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Old 9th November 2011, 10:52 AM   #41
Elias is offline Elias  Finland
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Originally Posted by graaf View Post
no pillow needed - OK I understand but my question is is it significantly different from the one with pillow trick and if yes - in what regards?

If we read through the diyaudio stereolith thread, we can refress our memory that the whole reason for the pillow direct sound blocker with The Cardboard was it's desired property of removal of listening distance dependency ! Back then, The Cardboard could not image without pillow at 2m distance, but could image at longer distances, say 5m.

Now, with x = 0.5, improvements have been achieved to this (for some reason hopefully appearing clearly to me some time soon) because the distance dependency appears to have diminished ! x = 0.5 images also at 2m, and at 5m too !

- Elias
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Old 9th November 2011, 11:06 AM   #42
graaf is offline graaf  Poland
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Originally Posted by Elias View Post
If we read through the diyaudio stereolith thread, we can refress our memory that the whole reason for the pillow direct sound blocker with The Cardboard was it's desired property of removal of listening distance dependency ! Back then, The Cardboard could not image without pillow at 2m distance, but could image at longer distances, say 5m.

Now, with x = 0.5, improvements have been achieved to this (for some reason hopefully appearing clearly to me some time soon) because the distance dependency appears to have diminished ! x = 0.5 images also at 2m, and at 5m too !
- Elias
I see - so the X0.5 circuit is there functionally instead of the sound blocker and sound-wise - as far as spatial presentation is concerned - the X0.5 and pillowed back-to-back are basically the same - have I understood You correctly?
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Old 9th November 2011, 11:30 AM   #43
Elias is offline Elias  Finland
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Originally Posted by graaf View Post
I see - so the X0.5 circuit is there functionally instead of the sound blocker and sound-wise - as far as spatial presentation is concerned - the X0.5 and pillowed back-to-back are basically the same - have I understood You correctly?
They are not the same in perceptual sense, not even close ! The difference is big !

Now I understand something was lacking with The Cardboard and the pillow. It's the naturalness of the center panned image !

Because:
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Originally Posted by Elias View Post
For example true mono signal is reproduced by Single Speaker Stereo (SSS) from a single location (Natural !), whereas by conventional three speaker spread stereo it is reproduced from three distinctive locations (Not natural !).

- Elias
This is also true between x = 0.5 and The Cardboard and the pillow. Earlier center panned image was relying on fragile phantom imaging theorem, but now it appears as a real sound source. And because center panned image = mono, and because x = 0.5 generates a true mono source, it is much better !

This is most apparent with natural sounds, like human vocals singing which are usually panned at the center (appears as mono). Let's not forget perception of the human sound has been evoluted during millions of years, long before musical instruments took place, and perception of it has been perfected so any anomalies in reproduction of human sound is the easiest to detect.


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Old 9th November 2011, 11:37 AM   #44
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Originally Posted by Elias View Post
Let's not invent problems where there may not be real problems !
Let's not ignore possible issues without having any real measurements. In theory inverted phase will have the said high pass effect. We have to find out if it is significant or not.

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The low freq directivity pattern depends on the amplitude and phase of the stereo input signals L and R. It will shift from monopole to cardioid to dipole when introducing a phase reverse. However, in a typical stereo recording there is no phase reversals at the low freqs !
Yes but the matrix introduces inverted phase. The higher x the more inverted phase components come into play.
I think it would be beneficial to have only positive vectors. This would have no negative effect on tonality. The (not so) simple question is what vectors are best? The original Stereolith radiates too much energy from the center.

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Originally Posted by Elias View Post
In addition, at high freqs the cabinet and element size affects the directivity more than input signal.
That's the problem, omni at low frequencies and increasing directivity at higher frequencies.
We probably want to achieve some reasonable SPL too (FRS8 is a no-go here), so driver size becomes an issue - or could it even help?

Last edited by markus76; 9th November 2011 at 11:41 AM.
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Old 9th November 2011, 12:10 PM   #45
graaf is offline graaf  Poland
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Quote:
Originally Posted by Elias View Post
They are not the same in perceptual sense, not even close ! The difference is big !

Now I understand something was lacking with The Cardboard and the pillow. It's the naturalness of the center panned image !
I see - so the center image sounds unnatural with pillow and not so with X0.5

but how can it be "because":
Quote:
Originally Posted by Elias View Post
For example true mono signal is reproduced by Single Speaker Stereo (SSS) from a single location (Natural !), whereas by conventional three speaker spread stereo it is reproduced from three distinctive locations (Not natural !).
I can see it as important difference from three-speaker trinaural indeed but I can't see any analogy between three-box trinaural and one-box two-channel back-to-back
can You explain?


Quote:
Originally Posted by Elias View Post
This is also true between x = 0.5 and The Cardboard and the pillow. Earlier center panned image was relying on fragile phantom imaging theorem
why fragile? in the absence of any conflicting cues characteristic for stereo, trinaural and so on?
in my experience all images projected by back-to-back are rather very robust, You can turn Your head and walk around the room and everything stays in place

so what kind of fragility do You mean?

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but now it appears as a real sound source.
but it is real only exactly for one case of the middle point of the stage

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because x = 0.5 generates a true mono source
true in what sense? as opposed to what? is L+R not true mono in comparison? why?

anyway, we have been told already long time ago that any matrix derivations of center channel would be inevitably flawed because the center channel ideally has to carry only the information that is common to the L and R, not simple sum of L and R, even if it is divided by 2

can You comment on that point either?
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Old 9th November 2011, 12:46 PM   #46
Elias is offline Elias  Finland
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Originally Posted by graaf View Post
I can see it as important difference from three-speaker trinaural indeed but I can't see any analogy between three-box trinaural and one-box two-channel back-to-back
can You explain?




why fragile? in the absence of any conflicting cues characteristic for stereo, trinaural and so on?
in my experience all images projected by back-to-back are rather very robust, You can turn Your head and walk around the room and everything stays in place

so what kind of fragility do You mean?



but it is real only exactly for one case of the middle point of the stage



true in what sense? as opposed to what? is L+R not true mono in comparison? why?

anyway, we have been told already long time ago that any matrix derivations of center channel would be inevitably flawed because the center channel ideally has to carry only the information that is common to the L and R, not simple sum of L and R, even if it is divided by 2

can You comment on that point either?

The problem with center panned image with The Cardboard may have been exactly what was removed by the pillow, the direct sound is undefined as it's off axis sound (of the side elements), so at mid-high freqs it was relying solely on side wall reflections, which in turn makes it's performance comparaple with conventional two speaker stereo triangle in terms of phantom imaging. Thus it's fragile for a center panned image.

In SSS center panned image comes from a single location at all freqs ! This is a virtue.


- Elias
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Old 9th November 2011, 12:50 PM   #47
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Originally Posted by graaf View Post
but it is real only exactly for one case of the middle point of the stage

True, but for a conventional two speaker triangle center panned image is the worst scenario ! For SSS it is the best scenario !

As I said, for natural reproduction of the most important sounds, like vocals, true center source is an improvement because vocals are commonly mixed as mono in the center.

For me it appears counterproductive to spread the speakers far away, if the goal is to reproduce something in the center

- Elias
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Last edited by Elias; 9th November 2011 at 12:52 PM.
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Old 9th November 2011, 01:03 PM   #48
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For me it appears counterproductive to spread the speakers far away, if the goal is to reproduce something in the center

- Elias
I agree. Having a real center speaker is the most significant reason why I think about this single stereo speaker concept at all.
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Old 9th November 2011, 02:31 PM   #49
Elias is offline Elias  Finland
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Quote:
Originally Posted by Frank Berry View Post
This has been done for decades.
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Originally Posted by graaf View Post
the wheel reinvented once again?
Quote:
Originally Posted by Soundminded View Post
The idea is hardly novel.

If a design of a small two way bookshelf loudspeaker were presented instead, the responses would hardly be of this kind

So what is the problem now ?


- Elias
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Old 9th November 2011, 02:55 PM   #50
graaf is offline graaf  Poland
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Quote:
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The problem with center panned image with The Cardboard may have been exactly what was removed by the pillow,
yes I am confused - so was it removed or wasn't? does there remain a problem in spite of the pillow in comparison to "SSS" or not?

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For me it appears counterproductive to spread the speakers far away, if the goal is to reproduce something in the center
- Elias
well, in case of headphones sound sources are as much to the sides as it gets - typically at 90 degrees - have You any problems with center phantoms when You listen through headphones?
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Last edited by graaf; 9th November 2011 at 03:07 PM.
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