If I have followed you correctly, you are speaking about a mono signal reproduced in a stereo system, right? What sense does it make to have that signal imaged anywhere else than on your center line between both speakers?
Rudolf
Yes, true mono signal on stereo playback. It's not intended for that to happen, it's merely a consequence of high quality playback - it serves as a marker, a test that a certain standard of reproduction has been achieved.
If you listen on the centre line, obviously that's where the image will lie, for any reasonable system; if you then start to move sideways with conventional quality 'in play' the image will sustain to a certain point, and then collapse into the nearer speaker, the sound will obviously be originating from the drivers. The higher quality of playback stops this collapse happening, at all times ...
If you listen on the centre line, obviously that's where the image will lie, for any reasonable system; if you then start to move sideways with conventional quality 'in play' the image will sustain to a certain point, and then collapse into the nearer speaker, the sound will obviously be originating from the drivers. The higher quality of playback stops this collapse happening, at all times ...
I think it's a higher brain function and not the quality of playback that prevents image collapse. What might be happening: Once your brain is locked onto a specific location for a sound, it doesn't let go although there's new input suggesting otherwise. You know it has to come from the center between the speakers, right? Have you ever done that test blindfolded? I bet the outcome will be very different from your past experiments.
On the other hand, in one of the Litovsky studies cited earlier there was a person that couldn't discriminate two clicks beyond a delay of 45-50ms. Everybody else could discriminate clicks only 5-10ms apart.
Because I've experienced this effect over and over again, on a number of setups I know it by heart: if the quality is not there then the effect won't happen. Wanting it to happen, wishing it to happen, believing you've done the right things to allow it to manifest, makes not an ounce of difference - it will resolutely refuse to behave, to give you "invisible speakers". This can lead to frustration, to the point of feeling like going up to a piece of the gear and giving it a good solid kick!
Remember, the image follows a directly forward looking vision -- another way of thinking of it is that if you had a line of chairs either side of the normal listening position, to beyond the speakers on each side, and had a person sitting on each seat, all looking directly foward, not towards the centre of the speakers - they would all experience exactly the same acoustic image in front of them.
I have done this with closed eyes, shuffling side to side, beyond the speakers, and the image tracks with me.
The point is, the experience is so different from normal that when it happens it's day vs. night, subjectively. Early in the piece I thought it may be something that only a limited number of people could trigger on, but Pano's and other's accounts indicate that it should be fairly general ...
Remember, the image follows a directly forward looking vision -- another way of thinking of it is that if you had a line of chairs either side of the normal listening position, to beyond the speakers on each side, and had a person sitting on each seat, all looking directly foward, not towards the centre of the speakers - they would all experience exactly the same acoustic image in front of them.
I have done this with closed eyes, shuffling side to side, beyond the speakers, and the image tracks with me.
The point is, the experience is so different from normal that when it happens it's day vs. night, subjectively. Early in the piece I thought it may be something that only a limited number of people could trigger on, but Pano's and other's accounts indicate that it should be fairly general ...
Yes, high level brain processes taking completely over although other processes tell something completely different, is fairly normal, e.g ventriloquist effect.
Do the blind testing I had suggested: Have yourself blindfolded, turn around a couple of times until you loose control which direction you're facing, have a second person guide you a couple of feet in one direction, play the signal and try to localize it by pointing your finger at it, then remove the blindfold and check how well you did.
Do the blind testing I had suggested: Have yourself blindfolded, turn around a couple of times until you loose control which direction you're facing, have a second person guide you a couple of feet in one direction, play the signal and try to localize it by pointing your finger at it, then remove the blindfold and check how well you did.
Interestingly enough, that's exactly what I've suggested a number of times, in a number of posts. And, the result will be that the person can't localise it - meaning, that they can point to where it is that the sound appears to be coming from, as in, I hear a piano playing over there, and the drums are in that place - but if asked to point to the speakers the response will just be a wild guess ...
Yes, that's the easy one.
In my rather crappy system the sound will only originate from the nearer speaker in situations where level/time trading doesn't work well enough. For most of the time the center phantom stays behind the speaker plane and somewhere between the speakers - even if I stand in front of the right or left speaker.
This has very much to do with the driver directivity and radiation patterns - and almost nothing with the overall equipment quality.
Rudolf
The reason to use mono for such tests is pretty obvious - there is, there can be only the centre phantom, unless there is some major imbalance or outright problem with one channel vs. the other.
I'm sure more specialised driver and carcase construction will alter the subjective impression to some degree - I've never played with horns, for example - all my adventures have been with very boring, extremely conventional 2 way and single driver setups. And, with those the phantom centre tracks with the position of the listener - if I stand in front of the right speaker the phantom image will lie exactly in line with the right speaker, but beyond it - the phrase seems to be that the image floats free of the speaker, and that's exactly the illusion produced: the speaker and the sound produced beyond it are completely unconnected, one could knock the speaker over onto its face and it would make no difference to what you're hearing, is the impression given.
Again, this only happens when the quality is there sufficiently - if the standard drops then the above scenario evaporates, and there is just an obvious, conventional speaker producing sound in front of you ...
I'm sure more specialised driver and carcase construction will alter the subjective impression to some degree - I've never played with horns, for example - all my adventures have been with very boring, extremely conventional 2 way and single driver setups. And, with those the phantom centre tracks with the position of the listener - if I stand in front of the right speaker the phantom image will lie exactly in line with the right speaker, but beyond it - the phrase seems to be that the image floats free of the speaker, and that's exactly the illusion produced: the speaker and the sound produced beyond it are completely unconnected, one could knock the speaker over onto its face and it would make no difference to what you're hearing, is the impression given.
Again, this only happens when the quality is there sufficiently - if the standard drops then the above scenario evaporates, and there is just an obvious, conventional speaker producing sound in front of you ...
My experience is a little different from Frank's, if I understand him correctly. For me it was the phantom center staying in the same spot while I moved around in front of the stereo pair. It stayed stable in a position about 1M behind the speakers. It wasn't 100% stable or perfect - there was some shifting, but still quite surprising to hear. It's one of those "But wait! Speakers don't do that." moments. Even walking up to the left speaker's left side the phantom image stayed centered about 1M behind the pair. It sort of made my brain hurt, because it's "impossible." 
This was such a surprise the first time I heard it that I'll never forget it. Not many speakers can do it. I suppose the electronics need to be up to par as well, but can't really verify that.
This was such a surprise the first time I heard it that I'll never forget it. Not many speakers can do it. I suppose the electronics need to be up to par as well, but can't really verify that.
I think we're on the same page, Pano. The image always exists separate from the speakers, and always when I've heard it it's well behind the speakers. What will sound totally bizarre to some people is that I've been able to stand literally inches away from the front of the speaker, and lean forward so my head is well forward over the top of the speaker on that side; yet the illusion still remains - amazing stuff!! To me, the obvious answer is that the sound field being produced is so well 'disciplined' with respect to what the ear/brain expects to hear that the mind is happy to hang on to the illusion.
The key thing would have been to do the moving around with a true mono track playing, that's what makes it easy to perceive this sideways shifting of the image as a totality. With strong stereo separation of the left and right signals, it would be far less a feature of what one hears ...
Edit: Pano has come from the angle of optimising the speaker, myself from looking at the system as a totality, working out where the weaknesses are that are dragging down the quality, in the key areas that cause the illusion to collapse. We end up with the same result, which to me says that it's all about that getting that sufficient quality, by whatever means. A number of times I hear other people's systems playing, and I think, Gee, that's close, that's mighty close to being there, it just needs a liiiittle bit more and it's over the line ...
The key thing would have been to do the moving around with a true mono track playing, that's what makes it easy to perceive this sideways shifting of the image as a totality. With strong stereo separation of the left and right signals, it would be far less a feature of what one hears ...
Edit: Pano has come from the angle of optimising the speaker, myself from looking at the system as a totality, working out where the weaknesses are that are dragging down the quality, in the key areas that cause the illusion to collapse. We end up with the same result, which to me says that it's all about that getting that sufficient quality, by whatever means. A number of times I hear other people's systems playing, and I think, Gee, that's close, that's mighty close to being there, it just needs a liiiittle bit more and it's over the line ...
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Another way of looking at the situation is that the ear/brain is reacting to the sound field that it encounters, not to speakers that happen to be producing that sound field. Which is why multi-channel if really well done will also do the job, the amount of sound information 'meaningful' to the recorded event is enough to mask the fact that mechanical drivers, located at certain spots, are producing the information - if the drivers give away too many clues that they are the "culprits", trying to fake it, then the illusion fails. Normal stereo has only 2 directly facing baffles to do this job, so they have to be on their best behaviour to make it happen ...
can You please describe some of them? Types of speakers and of rooms and of used stereo geometry?
Have they anything in common besides (possibly) the low level of IM or other distortions?
Nothing really special in the audiophile sense about the setups other than the level and type of tweaking: the speakers have until recently been classic 2-ways, bookshelf up to floorstanding, with simple, straightforward crossovers. Tweeters were non-metal domes, and normal cone; all poor connections inside the carcase were eliminated, and more recent examples had their crossover electrolytics replaced with Solen units.
An essential was always ensuring good coupling to heavy mass, homemade, sandfilled concrete stands for the bookshelfs using Blu-Tack to link speaker and support, with spike coupling to the floor. I also used extra mass damping on top of the speakers - the goal was to make pushing on the side of the speaker feel like pushing on a very heavy piece of furniture.
The rooms have been various types: cathedral ceiling in one, with carpet; wood lined, with timber floor in another, and glass most of the way down one side. Geometries I have not worried about, no toe-in and such-like, for no other reason than I wasn't interested in such things ...
Key to the electronics side was simplicity: no pre-amp, no input switching, until recently digital volume control directly driving power amp - complexity and extra fussiness breeds distortion artifacts.
No, very little of the normal audiophile "gadgets" - original cable was van der Hul, but that was just because I caught "that" bug at the time, and I've used it for a fair bit of the time, just because it was there. In essence, I look for weaknesses throughout the system and solve, improve them; rather than have a fetish about using "magic" parts.
The principle has always been tracking down 'the weakest link in the chain' thing - if you knock each one over, eventually the system gets good enough to work to the level that I'm talking about ...
An essential was always ensuring good coupling to heavy mass, homemade, sandfilled concrete stands for the bookshelfs using Blu-Tack to link speaker and support, with spike coupling to the floor. I also used extra mass damping on top of the speakers - the goal was to make pushing on the side of the speaker feel like pushing on a very heavy piece of furniture.
The rooms have been various types: cathedral ceiling in one, with carpet; wood lined, with timber floor in another, and glass most of the way down one side. Geometries I have not worried about, no toe-in and such-like, for no other reason than I wasn't interested in such things ...
Key to the electronics side was simplicity: no pre-amp, no input switching, until recently digital volume control directly driving power amp - complexity and extra fussiness breeds distortion artifacts.
No, very little of the normal audiophile "gadgets" - original cable was van der Hul, but that was just because I caught "that" bug at the time, and I've used it for a fair bit of the time, just because it was there. In essence, I look for weaknesses throughout the system and solve, improve them; rather than have a fetish about using "magic" parts.
The principle has always been tracking down 'the weakest link in the chain' thing - if you knock each one over, eventually the system gets good enough to work to the level that I'm talking about ...
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I see, I wonder though how this tweaking translates to the needed reduction of distortions, in other words how it fits into Your low level of distortion hypothesis
You're probably describing a sound field where there're so many confusing/ambiguous/missing localization cues that the brain simply creates its own reality (not that it wouldn't do that all the time anyway) that has nothing or very little to do with the real situation.
Could you post an impulse response measured at the listening position from a room (system) that has the said qualities?
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yeah, perhaps it's a matter of those high level brain processes, it appears that it's better to have some and that systems like FCUFS are simply only for people with some high level brain processes
Here, http://www.diyaudio.com/forums/lounge/200865-sound-quality-vs-measurements-943.html#post3526022, I explain the key aspects I worry about - and there's some interesting material in the following posts relating to the points made ...
interesting discussion
I do not put into question anything of what You say out of Your personal experience but still I would like to see some scientific explanations of what is going on, some scientifically explained link between what You do and levels of identifiable distortions of particular types and how it affects imaging/soundstaging of an audio system
This might be something that fits better in the other discussion, but I've long thought that physics / math and measurements..while able to offer some insight into the things we hear, really can't give us the whole story. Individual hearing and subjectivity always creep into it because..well...we're human beings and we're different.
Our hearing mechanisms might all operate on the same basic principles, but I think there's quite a bit that we just can't measure or illustrate because we just don't have the techniques to properly translate the experience of what something really sounds like into an image or formula that can be pasted into a jpg and conferred to others. We can get pretty close...and we can glean some useful information..but in the end, what do we always do? Once we're done measuring and calculating and fussing with charts, we plug the thing in and see what it sounds like.
For instance, if I have one pair of speakers where I play a recording that has recorded bird song...and on the first pair of speakers that sound comes pretty much only from the front and lies kinda flat against the wall, but then I try a second set and the bird song pops out all over the room in various locations, what do I set my o-scope to so that I can see what causes that, or share that with others?
Don't get me wrong, I think measurements and scientific study and information is immensely valuable, I just think sometimes we skew that value a little farther out of proportion with the real goal, which is a pleasant listening experience....which is all so subjective ...some of you are now thinking "That's why I like FCUFS!" and others are like "That's why I like surround sound!" and still others are like "That's why I like my FPB-600s and Wilson X1s!"
Sometimes, when asked why someone prefers something, there's just no chart that can be reached for.