Engineering the stereo image

[preiter]

I don't know if there are any sound engineers reading the forum, but I was curious about how modern recordings were engineered, especially with respect to creating the stereo image.

If each musician is being recorded separately on individual tracks, where does the stereo image come from? Is it created by the sound engineer in the studio?

[jneutron]

Originally posted by preiter
I don't know if there are any sound engineers reading the forum, but I was curious about how modern recordings were engineered, especially with respect to creating the stereo image.

If each musician is being recorded separately on individual tracks, where does the stereo image come from? Is it created by the sound engineer in the studio?

An engineer by the name of Adolpho Waring created a circuit that is used to create the imaging. A complex system, is was designed around circulator theory, somewhat like that used during ww2 for microwave waveguides. It creates the proper stimulus via a 3-d topological construct that was modelled correctly in the 50's, I believe, and adapted in the early 70's to work using modern opamps (at that time of course), with a circuit which cross couples the leading edges through some algorithms...this has been adapted by use of the Z transform theory today, in a system blending topology...current mixdown soundboards have this feature included, albeit the technology is sufficiently advanced that one is now able to use exactly one knob on the front panel to alter the direction of the source image in the soundfield..

So, the simple answer is this: All the individual tracks are dropped into the soundboard, put through a freakin WARING BLENDER, and the garbage output stream is what you buy in the store..

Seriously, they just use a pan pot, and alter the amplitude from side to side. That is not a stimulus that occurs in nature..

Cheers, John

[poobah]

prieter,

Look on the cables thread "lies and myths" right now, there's some interesting chatter about imaging... or more precisely the lack of it...

[rdf]

Originally posted by jneutron

Seriously, they just use a pan pot, and alter the amplitude from side to side. That is not a stimulus that occurs in nature..

Cheers, John

Nope: http://en.wikipedia.org/wiki/3D_audio_effect. Welcome to the Nineties.

[phn]

I have a test CD and there's this tapping sound that goes to the right and then moves behind the listener. Something such. At least that's what the guy on the disc tells us. It sounds like he's for real. I guess I wasn't in the mood. I mean, I don't understand those behind the viewer speakers in surround set-ups. The action takes place on the screen in front of me. Why would there be sound coming from behind? Makes no sense. Is the idea that I should turn around and look? Shouldn't there then be another screen behind me? Too many questions.

Maybe I'll give the test CD a serious try one day.

[jneutron]

Originally posted by rdf


Nope: http://en.wikipedia.org/wiki/3D_audio_effect. Welcome to the Nineties.

Examine carefully the basis for their understandings, and the equations they are using.

Note they use R and L...the right and left information.

That is all...they play with phase, they may even play with amplitude, although in the brief view, I didn't see that, I assume that some really do...

Where in their signal processing, is the angular variable for the origional source to the mikes, where is the angle/depth vs amplitude variable..

On the reproducing end, where is the speaker placement angle, where is the distance to listener, where is the speaker angular dispersion function, where is the correction function for the two point source to nulled three false images???? (unless of course, you want to put an absorbant septum on your face).

What has been done is rudimentary. It is all a simple shell game to try to fool your ears into believing it's there...it is not good.

And, nowhere do these equations have a frequency dependent component.

As I said, rudimentary. And darn near all the positional information is tossed in the garbage as a result of mono compatibility.

Even implimenting the correct ITD/IID algorithms is a small step, as it does not correct for the cross head images that we are supposed to ignore.

Give me a year or two, and I think I can explain image localization stability theory to them.

If you wish, I can go into more depth tomorrow....right now, I carpool..

"welcome to the nineties.." that was funny..I gotta give you that..

What I did 10 years ago will be SOTA in another decade..not in audio, of course..(you'd be suprised how complex refrigerator magnets are... )

Cheers, John

ps...it's all fun, I'm not offended..hope you aren't either..

[poobah]

It's all about the owls...

[rdf]

Originally posted by jneutron


ps...it's all fun, I'm not offended..hope you aren't either..

Not at all! I'ld be very interested in reading more, with the proviso that lacking the background on your personal approach it's reading in half sentences right now. A bit like walking into the middle of a conversation. I do think the simplicity of the Wikipedia format might lead to an underestimation of the degree of sophistication some of these techniques employ but that's for tomorrow.

[poobah]

So rdf,

Are there actually studios using these gizmos on a track by track basis to array the instruments in an image?

John can nitpick the exact algorithm all day long (he will BTW), but hell, that's a start.

Short of 2 mics in foam head and headphones, it will always be an illusion, but a better one is better one.

[rdf]

Absolutely. One manufacturer's example:

http://www.qsound.com/2002/spotlight/main2a.asp (Princess Patricia's Canadian Light Infantry Band!?!)

To judge by listening experience only (appreciation in advance to anyone who can confirm it) but I'm certain movie surround algorithms make heavy use of this technique.