Sweet spot ?

[PeterSt]

I hope it is allowed to come up with another more or less controversial post, and I realize that I will be talking to myself merely. However, hopefully that latter will change in due time ...

All springs from what I described in this post : Re: SQ of 1.186, best ever! (Again) so I assume this post as "knowledge";
Say it is about flying seagulls and what it takes to perceive those.

In the far end this is about 3D perceivement of audio of which I feel I am getting fairly close to that.
Notice how I describe 3D in this case :

Dimension-1 : Left/Right;
Dimension-2 : Height;
Dimension-3 : Depth.

D-2 is a sneaky one because everybody will be able to say that he perceives that right now, while it is easy to be fooled by what you perceive of it. I mean, the whole picture can easily be lower or higher by means of small changes in the chain, and this sure is not the D-2 I am talking about.
It also can easily be how instruments picture at certain heights relative to eachother, and I am also not talking about that although it would be the better version than the one first mentioned in this paragraph. So explain this one specifically and how it can look like the D-2 while it actually is not :
High frequencies assumed to be more directional than the lower ones, any instrument showing the higher frequencies will be "able" to draw better towards the speaker, which means that it can play lower in that height-dimension space; when things really are not the best, the instrument will jump up and down (and from the speaker towards the middle) when the higher frequencies are in order or stay out. So while theory easily tells that this can as easily happen, this is not right and should not be. Thus, instruments should stay where they are, no matter whether they accidentally play higher frequencies or not.
This all assumed :

Again when things are right, the music will never go out of the boundaries of the room. If that happens after all you'll have some Lyngdorf in your chain and will work towards a brain damage - which is up to you.
The music you hear for a great deal emerges from reflections to walls, ceiling and floor, and when you damped all so much that *that* does not happen this topic probably is not for you. Or maybe in a later stage, but right now I see "this topic" happening / being in order for reflections only.


What I saw happening lately already, is a sort of tunnel effect when listening further back in the room. Hard to describe, but as if there's a more major beam where the sound is captured in and wich officially will be true when looking at how (types of) speakers radiate (or "throw"). Mine are horns, so they throw far (so to speak).
This tunnel effect feels like once you stay in that beam it is not quite possible to notice where the sound comes from were it for D-3 (depth), although it sure is so that our micro computing brain will tell it is from the opposite of the room where the speakers are. Here the reflections play a role because we are able to compute the difference from direct sound versus reflected ones and the net result is the distance of the speaker we thus now. This is not entirely true and more complicated but for my story it is more important that the reflections at least have a role in this, because it is the reflections I want to use and utilize.

What I already know is that and the distance of the speakers to eachother and the listening distance to the speakers really need not to be like we learned. This with the clear notice that this for 100% depends on the quality of the playback - but now with the "seagull experience" in mind (let's say the playback must me more than extremely good for whatever that means anno February 2014) and for me this is easily proven by my speakers being 6 meters apart with normal experience as we know it at 4 meters listening distance - that experience being just as goog at 12 meters listening distance. This coincides with my personal wish of not evenb *liking* sweet spots including not liking to be in the middle at all. And again, over here this is not necessary at all.
But :

This is outside the seagull experience.
Remember : this is about a seagul being able to fly towards you very sharply defined and the ceiling is the reflecting instance that makes it happen. So what you perceive from it is the seagul flying right under the ceiling and across the 12 meters it flies towards you. Not an eyes closed imagination, but just enabling pointing out where it flies. Now :
This will NOT happen when listening at 4 meters distance and *if* it does it flies 4 meters only (instead of 12) and if not that it's imagination (illusion !) after all.
Small disclaimer because I don't know at this moment : QSound will be able to let fly the seagull 12 meters after all but now over your head to the back of the room. So I am explicitly not talking about QSound, BUT all can have gone as far as no QSound needed anymore because all is in the (phase difference) "data" already. And don't underestimate this latter, because all my theories are based upon that (mind the name "Phasure").

Without reflections the seagull will still be able to fly but it will be way more difficult. This is because our means of localisation makes use of phase angle differences, while the radiators doing that are not suitable for 3D because of their 2D theoretical behaviour (= 2 speakers). Still this can happen with a sufficient amount of different frequencies at the same time, OR when more than two radiators are used in a consistent way. This latter is beyond our subject (but actually the base of it) but envision that the reflections (or better the walls) are that next radiator and because we can discern reflections from first tiem arrival sound, we can "work" with that in the aid of localisation. Try to see this as one speaker won't position the object (seagull), two will do somewhat but can't do it correctly, three will do it better again, for again better and so on. In the end a 5.1 etc. system is made for such things obviously, but this is by changing the signal; what we talk about here is explicitly using two speakers which consistently radiate the signal with the emphasis on the walls "making" that consistent for us (the reflections all have a distance and we know that) and thus *not* using 10 or so speakers because that would not make it consistent (not even with time delayed different signals where all remain rigid point sources).

The tunnel (or beam) I have been talking about is a tunnel with a width. Again tough to explain, but this tunnel is not detected by means of walking and noticing that you just walked out of the beam, but you can hear it already when stending still somewhere - but within the boundaries of the beam;
What I'm after today, is where the *height* of the beam resides. So what I noticed already is that when being more into the room (towards the speakers) things "fly less". The logic of this IMO is in the reflecting back wall which must aid. So, side walls may reflect and can help to locate the seagull in the D-1 (L/R) space, they might help a very little because of smeared reflections (think a few meter long beam hitting the side wall), but it is logic that the back wall brings the information of the depth, because that's the one reflecting in that D-3 space. And the possible crux : the farther we are away from the back wall, the more the sound will be snowed under by the direct sound of the speaker.
For this I have another accidental observation :
While I can't detect any standing waves anywhere (not audibly and not by means of SPL meter), there is one odd small corner in that back wall, and when I listen with my head in that corner, all becomes totally consistent and way better and like wearing headphones. Sound only comes from that corner and I am not able to detect that the sound actually comes from the opposite side of the room, 12 meters further.
What I'm trying to say, is that this is totally undistorted, not bloomed by too much bass or anything but obviously I am listening to sound captured in a corner and/but it shows the opposite of listening to the speakers. Now obviously there is an "in the middlle of that" as well, and this is not 6 meters but maybe half a meter from the back wall. So, the relation between 11.5 meter distance direct sound and 0.5 meter distance reflected sound and there the SPL of both is equal. Well, almost, because right in that corner it is, and at 0.5 meter distance it is less again BUT this now just allows for those reflections for be deteced as such, while in the mean time the changed phase of it (180 degrees to begin with) helps localising.

Someone still here ?
No ? good. Then I can continue.


Apart from now perceiving all flying around (not only seagulls), this topic is deliberately theory. So, all I noticed in some glance is that the seagull can fly towards you just onder that ceiling, and my brief notice that it depends on my own distance to the speakers - but (theoretically !) better : the relation of that with the back wall incorporated.
What bugs me (or will bug me I think) is that we will be able to hear that the radiating device (the speaker) is more far away than the sound we perceive from it (can you follow ?).
So what I will try to sort out is what the "sweet line" is allowed to be (or what the margin in it is) in order to see both flying seagulls and not perceive the so far away speakers. Could be a matter of playing louder - I don't know yet.

If you don't see me back here, all failed.
Peter

[christoffe]

Hi Peter,

An interesting article to read.

Even a 5mm of speaker movement will/might have a severe impact of the SQ. Overall, it is a "trial and error" game. The distance between the speakers is one of the most underestimated items.

See also:
http://www.gcaudio.com/resources/howtos/speakerplacement.html

Joachim

EDIT: Our CD music is a reproduction of the sound recorded ...... . For a replay of a seagull flight towards you a third speaker behind the listening position is required due to the different SPL of that flight. THe SPL of a seagull flight increases with the distance from the speakers. To listen to a flight from left to right it is no problem, but ...... .

A sample: http://www.youtube.com/watch?v=a1O5UtLWH3Y

[PeterSt]

Hey Joachim,

EDIT: Our CD music is a reproduction of the sound recorded ...... . For a replay of a seagull flight towards you a third speaker behind the listening position is required due to the different SPL of that flight. THe SPL of a seagull flight increases with the distance from the speakers. To listen to a flight from left to right it is no problem, but ...... .

You are correct of course, and I guess that's exactly my described problem. Well, sort of;

The SPL (or general loudness) of the seagull increases clearly (so I see it coming flying in from the sea), but still it doesn't work out well, because the louder SPL springs from the speaker and we keep noticing that. Well, to some degree (pun). Please see upcoming small post.

Regards,
Peter

[PeterSt]

Yesterday I performed a few chlidish tests. Childish because it looks like that to begin with, but also because it is not much scientific. That is ... there's too much logic in it to even start trying. Still I never did that before, and I only "could" do it because of my first post in here.

I have all hard walls and glass at all sides of the room. I observed the "phenomenon" without the seagull but different "sharp" music (the higher the frequency the better we can localise which is related to phase angles more easily being different hence more easy to detect).
On the side walls there are curtains and I felt or heard that with them open the effect would not work as well. This too I of course wrote out and it is about the beam implied by the width of beam radiated by the speaker against the side walls and while I said that could help somewhat, I now thought that would confuse when the back wall is to be explicitly used as "reflector". So I closed the curtains to the windows on the side walls.

First thing I now noticed explicitly that my little corner which is perceived as headphone like, can only work like that when you look into the corner. So you're looking the opposite way of the speakers. I already knew that, but never did anything with it. Now I did, and it brought me to the childish experiments;

I went to the middle of the back wall - which is just in between the speakers (though they are at 12 meters distance) and put my hands behind my ears as if I wanted to hear better. Well, this is to point out what I really did, which is put my hand in front of my ears making the shell of my hands the other way around. So easy to see : I wanted to capture the reflected sound of the back wall better.
Thus, just look towards the speakers, but your hands the other wat around in front of your ears;

What happens (in my sutuation) is that the phenomenon of being able to hear where the sound springs from (the plane of the speakers) shifted just over one meter. So, speakers were now at 11 meters distance and I needed to be around 0.5 meter from the back wall to not imply anomalies like a different colour of the sound or decreased highs.
I let do this by someone else in the room, and that she came up with the same location of the speakers.

I thought, okay, this is not the very best and we can improve on this by now turning around and facing the back wall, and now put your hand behind your ears to hear better as usual.
Now the sound was over 4 meters closer. That too was confirmed by the she.

While I could see myself making me some "ear devices" attached in front of my ears like the first test and walk around with that from now on, I did not see myself having similar devices behind my ears and from now on facing back walls. So while that would be the far better working solution, it isn't practical and thus no solution. Anyway :

I am not sure what I proved except for reflections sure working (which was a kind of obvious), but when the problem were to be that we keep on hearing where the sound really springs from, at least that position can be shifted far more towards you and with larger ear devices most probably even way more. So let's say that half of the room in my case - or 6 meters - is possible.
But then what ?

I am pretty sure that to eagle or whatever is going to fly from 12 meters towards me or IOW I don't think that now any sound will emerge ever behind that 6 meter plane. So if the eagles and seagulls and dinosaurs fly, they now will fly over a distance 6 meters only. At least that is what I think.
What I 100% sure did achieve though is that no single sound springs from the speaker any more, now matter how hard you try;
What I observed from it, but now facing the speakers and hands in front of my ears, so "physical detachment" was over 1 meter only, is a sort of confusing or obfuscating depth of sound source. Probably this is because of the one (higher) frequency reflecting better than the (lower) other and how phase relations (in the longitudinal plane) now don't fit anymore. You could say that instruments now became too fat but in that longitudinal plane (yea, that's a new one I guess).
But ...
I now must be careful because my back wall is not 90 degree angled in relation to the side walls and it is merely 80 degrees. This means that the reflections from left and right are mangled with, or at least will again create a wider beam similar to the beam I described from the side walls. Thus, obfuscating somewhat.

On some other note it can well be - or should be - that my room just is to long to really let it work well. I mean, when the room would be 5 meters I can imagine that I don't need to put my hands in front of my ears at all, because SPL against the back wall is high enough to observe it in normal fashion. Small problem with this : I would also be 4 meters from the speakers only, and maybe it all can be seen as a linear function and the room length doesn't matter (regarding this).

[PeterSt]

Last one on this for now :

By pure accident - and actually with the seagull it went exactly the same as I realized afterwards - I found the position of where all suddenly receives that super depth and indeed against the ceiling;

Not that it's worth anything to you all but this is at ~ 8 meters from the speakers which is 4 meters from the back wall ... BUT ... only when walking towards the backwall (so mind the positioning of ear shells).
Supposed this is official per means of speaker positioning :
Room is 8 (!) meters wide, just over 12 meters long, speakers are 6 meters apart and around 80cm from their back wall.
So yes, 8x8 should be some room mode but don't ask me whether this is related. Same with my position from the back wall which is 4 meters and which is half of 8 (two folded).

Stupid thing : at this 8 meters distance I can't be in the middle of the speakers because I then have to remove a (drinking) bar which probably is the last thing I will do.

Peter