Imaging "Outside The Box"

[jdm56]

Most of the time, the image produced by two speakers is confined to an imaginary line drawn from the left speaker to the right. If a given pair of speakers can reproduce solid, convincing images at any point along that line, they're doing pretty good. Sometimes the line is straight and sometimes it is bent in the middle, depending on whether the speakers are "forward" or "laid back". And some speakers produce vague images along the line, while others are razor sharp. And some can produce images behind the line. These speakers, we say, have good depth. But there is one aspect of two-channel imaging that in my experience is more or less constant. Others may disagree, but personally, I seldom experience image placement outside this imaginary line. That is, to the left of the left speaker or to the right of the right speaker.

Notice I said "seldom". Because I do have a few recordings that will at times image "outside the box"; sometimes extremely and startlingly so. My question is: "how is this accomplished? What factors are at work here. My feeling is there must be some kind of phase manipulation going on, some audio "hocus-pocus" if you will. Or perhaps it is just accidental!

And this leads to the next question: If this can be controlled, that is, if it's just a matter of the recording engineer pushing the right buttons or turning the right nobs, then why isn't it done more often. It is a very "cool" effect and could be used to widen the soundstage considerably.

[WMcD]

Psychoacoustics is a big issue and localization is a part of it. I looked at http://en.wikipedia.org/wiki/Sound_localization . This doesn't really answer the question.

In short, localization relies upon several factors including relative level, phase, and frequency response. Our outer ear (somewhat a directional horn) is involved.

There was one old technique for goosing imaging which played with the head transfer function. It was in Audio or Stereo Review.

Consider what happens when a source is hard left at 90 degrees. The sound hits the left ear. Then there is a delay and attenuation when it get to the right ear. Therefore, even hard left is picked up by the right ear with delay and attenuation. OTOH, if we plug our right ear, we don't hear everything as being hard left. The conculusion is that the head transfer function is a big part of localization.

Roughly, when a speaker is, say 30 degrees, left off center axis, we are getting a weaker verision of that full 90 degree off axis function. The sound to the right ear is not quite as delayed and not quite as attenuated. We sense that the speaker is only 30 degrees off axis. But maybe we can fool around and at least decrease the amount of left channel leaking in our right ear and make it seem more like it is 90 degrees off axis.

So we take a (usually midrange) "effect" speaker and feed it with the left channel from our amp but wired backwards. We put that one about a head width behind the right speaker. Now that effect speaker output arrives, delayed, to our right ear. It essentially nulls out (180 degrees out of phase) the genuine left channel which gets to our right ear. So the head transfer function is closer to the 90 degree situation. Of course we need the same set up on the other side too.

As you can imagine this fools the head transfer function and can tend to broaden out the sound stage. These days, it is not difficult to do the same with signal processing. I think that Carver was fooling with this.

There were some popular recordings in the early 1970s called Environments. One was a full side of an LP with breaking waves. Another was an aviary with birds. The birds would seem to be everywhere in the room. In my case, in the car, where I heard it on FM.

I suspect this is not used more because it may ??? rely on the exact placement of the speakers to get right. Also, it is somewhat hoaky. As much as we all like wonderful effects, it really does not add to the performance.

Now you know what I know.

Wm McD

[Coytee]

I'd wonder if and if so, how much the room might have to do with it?

sucky room = never hear it right

good room = might hear it properly if on good speakers??

(just wondering)

[Guest " "]

speaker placement is a controllable one.

putting a pair of speakers 1ft apart, and placing your head in between, would be ideal, if we we using a single full range speaker, but with multi-array speakers that have tweeters, mids, and woofers, there's whats refered to as a buble effect...which basically means there's a min distance needed away from the speakers before you are in the zone.

most folk place speakers at the 11:30 and 12:30 clock position of a room which requires even more of a distance before the zone can manifest itself.

placing your speakers in corners toed in, the 10:30 and 1:30 positions brings the zone closer to the front of the room.

[Groomlakearea51]

Phase, "good room", and proper placement seems to be the key. All other factors taken care of, in a "good room", the imaging (dependent upon the recording) will often exhibit some depth characteristics (if originally recored with those effects) as JDM mentioned. Most of the time, it's pretty much in the "horizontal" line. I've been able to get some better localization, or depth, using a second pair of speakers in a vertical array. Requires very careful work with volume control, etc., Since the second pair(s) are at a different distance from my ears as opposed to the primary source speakers, I guess I'm "mechanically" inducing this effect. I have to be careful though or I'll get comb filtering issues.

[Don Richard]

If one wants to "hear around" a set of speakers it is essential to locate those speakers away from the walls. Only then can the perception of depth and hearing beyond the width of the speakers occur clearly. This is partly because most recordings, especially those made these days, were mixed on near-field monitors set up in that manner. Speakers located in a corner or against a wall have their sound confined by the room boundaries, and we hear the resulting sound as being between those speakers. Much trial and error is involved in placing speakers so that "outside the box" imaging will occur and sound realistic.

[TNRabbit]

Speaker placement and room details play a HUGE part. You guys need to hear a pair of Polk Audio SDAs or Carver Amazings with Sonic Holography engaged....

[jdm56]

The most holographic imaging I've ever achieved myself was with a pair of Optimus Pro-77's from Radio Shack, set up on stands well out from the walls, in almost a near-field arrangement. No bass, but lots of depth and imaging magic. Too bad their tweeter was so lame. I'm sure much better results could be obtained with better mini-speakers, such as ADS L310's or something along those lines.

I guess another related question (not that the first ones have been answered yet[]) is how much of any given set-up's imaging performance could be described as accurately reproducing information on the recording, and how much is just a speaker/room induced effect? Especially the "outside the box" imaging; i.e. the (re)creation of images outside the plane of the speakers. And I guess what I'm still hoping to hear from some of you knowledgable audio dweebs (a compliment!) is what's going on when a system does just that. I recall watching one of my kids DVD's that had a scene with a jet on a runway. As the jet streaked from right to left, the image just kept on going beyond the left speaker -amazing! I don't hear that kind of eerie, beyond the speaker imaging in music as often as I do in movie effects, but I do hear it sometimes.

[Marvel]

My LS are about two feet in from the left and rightside walls, about 30 degrees apart (15 left and right of center). I have one album by a friend of mine, with one particular song that always surprises me. There is percussion which sounds like it is 60 degrees from center on the left. It isn't just a little outside, it is way to the left. It is almost unsettling.

This reminds me that I need to ask him about it.

Bruce

[jacksonbart]

Amused To Death, Roger Waters, track 4.

[jdm56]

My LS are about two feet in from the left and rightside walls, about 30 degrees apart (15 left and right of center). I have one album by a friend of mine, with one particular song that always surprises me. There is percussion which sounds like it is 60 degrees from center on the left. It isn't just a little outside, it is way to the left. It is almost unsettling.

This reminds me that I need to ask him about it.

Bruce

That's what I'm talking about! How do they do that? Unless somebody comes up with a better explanation, I'm going to go with phase manipulation. Of course, just saying that doesn't really explain the how, really. It'd probably be over my big, fat head anyway.[]

[Groomlakearea51]

Just a thought... I'm not sure... but if the recording folks add just a teeny weeny bit of reverb to a certain instrument at a certain point in the recording, it may be that what you hear is a sense of "depth". pschoacoustically, that could be the effect. Possible? Anyone have any ideas about that?

[TNRabbit]

Bob Carver used phase manipulation, delay, and frequency emphasis in combination to form Sonic Holography. Maye some magic smoke, too.... []

[tigerwoodKhorns]

Amused To Death, Roger Waters, track 4.

If your speakers are set up correctly and image well there is a voice on this track that you will hear either immediately to your left or several feet behind you to the left. I was able to hear it behind me when I had a pair of small towers set up in a large room well away from the walls.

[boom3]

The times I've experienced this were with very wide-dispersion speakers, relatively far from the sidewalls and back. In my present set-up my Corns are pretty close to the sidewalls, so I have not experienced this effect. I have heard the early Polk flagships speakers and yes, they do have this effect. The room I heard them in is far from optimal but I could hear it.

[tigerwoodKhorns]

The times I've experienced this were with very wide-dispersion speakers, relatively far from the sidewalls and back. In my present set-up my Corns are pretty close to the sidewalls, so I have not experienced this effect. I have heard the early Polk flagships speakers and yes, they do have this effect. The room I heard them in is far from optimal but I could hear it.

FWIW my speakers are about 12 feet apart and against the wall and they always image beyond the speakers. They are those junky B&W 800's that everyone says cost too much.

[jdm56]

My definition of "too much" keeps going up. Especially since the Palladiums came out! $20,000.00?[:S]

Bob Carver seems to be an "outside the box" kind of guy. Kind of like Paul Klipsch, only with different conclusions. Check out Bob's little cinema ribbons: http://www.sunfire.com/CR.htm I'll bet these little pups can pull off all manner of imaging hocus-pocus.

[tigerwoodKhorns]

My definition of "too much" keeps going up. Especially since the Palladiums came out! $20,000.00?

Bob Carver seems to be a "outside the box" kind of guy. Kind of like Paul Klipsch, only with different conclusions. Check out Bob's little cinema ribbons: http://www.sunfire.com/CR.htm I'll bet these little pups can pull off all manner of imaging hocus-pocus.

A local friend has the biggest collection of electrostats that you can imagine. He has a pair of Carvers stats that just sound awesome. I think they have a woofer on the bottom of the cabinet if I remember correctly. Very nice. He aslo has a little Carver subwoofer that looks like the prototype for the JL Audio Fathon. it is a little cube that juts puts out tone of bass.

[TNRabbit]

A local friend has the biggest collection of electrostats that you can imagine. He has a pair of Carvers stats that just sound awesome. I think they have a woofer on the bottom of the cabinet if I remember correctly. Very nice. He aslo has a little Carver subwoofer that looks like the prototype for the JL Audio Fathon. it is a little cube that juts puts out tone of bass.

FYI: Carver Amazing Loudspeakers (ALs) are "ribbons", not electrostatics. The ones with the downward-firing 10" woofer are the AL-III iteration (last ones made by Carver). I have a pair; they have a bleached-oak finish (custom).

You're right about the Sunfire subs; they were the first "micro" subs made...he sorta broke the mold with those. Pound for pound, probably one of the strongest outputs in the business. Not the best by any means, but they are pretty good, and you can run multiple subs out of sight.

[garymd]

In my experience, I get that "outside the box" effect all the time on my Cornwall setup and I believe it has to do with the fact that there is about 6 or 7 feet beyond the side of each speaker before you hit the side wall. I don't get this effect as often with my Khorns as they are crammed into the corners. I can't explain it in technical terms like some others here but my guess is the sound has room to move beyond the speakers and bounces off the side walls giving you that effect. Just a guess. I also hear a lot of sound behind me. I obviously have no acoustical treatments to deaden the sound in that room.