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24.13.230.11
In Reply to: RE: Revisiting Heyser posted by BigguyinATL on May 16, 2012 at 10:29:33
Hi
Dick was a brilliant man, I owe him much and now having gone through some of his unpublished work, there are many questions I would ask him if it were only possible.
I met him twice, once at JPL when I didn’t know who he was and again with Don and Carolyn Davis who had given me an excuse to leave the tradeshow booth at AES and go with.
I could only squeak out a few words that night at dinner, I was terribly aware of being in the presence of giants like Dick, Gene P, Don and others and me being about an inch tall.A friend was in charge of the Heyser library and it was for me a hair standing up on the back of my neck experience to go through that room and look at his test equipment and some of his unpublished work.
It was nice too eventually we were able to hire him and this month went on full time.
http://svconline.com/proav/acoustics_danley-sound-taps-top-acoustician/In reading thorough his work, it is clear he was big on seeing things interchangeably from one perspective to another, much like how mag&phase are one view of the event while the impulse response is another view of the same exact event.
Personally I believe Dick has gotten less credit than he deserves.
In another form I explained what I saw / see starting with post #2195, #2200, #2209 here;
http://www.diyaudio.com/forums/multi-way/195124-what-ideal-directivity-pattern-stereo-speakers-220.htmlAnyway, to me there are two phases of the problem, the “capture” and the “reproduction” and a “real” image requires both be correct.
He was correct in what he was saying too but a hologram is not necessary as compared to light, we are working with TINY dimensions relative to the wavelengths. SO many things depend on the acoustic size.We hear in 3d BUT we are totally unaware of that process or how different that is compared to a perfect microphone.
In Don Davis’s “in the ear” recordings shows with amazing clarity, if you measure what is inside your ear, you find the response has all kinds of changes and comb filtering depending on the incoming angle etc.
Our ears are nothing like “flat” and everything about them would appear to be a”flaw” if see through an measurement eye.
We hear NONE of those things, rather, this is all we have ever known and so instead of hearing the comb filtering, inter ear delay and all that stuff as “flaws” we hear what direction the sound is coming from, how high it is and how far away it is, 3D perception from a two point system which normally could only resolve one axis, with processing and direction dependent errors, we hear in 3D. Playing with these effects can trick your ears to a degree but never as strong as the real thing.To me, the reproduction side was he side where the “light went on” for me about 12 years ago.
As the full range horns at work got to be more and more like one driver a weird thing happened.
Playing a voice though one speaker, it got to be harder to tell exactly how far away the speaker was when my eyes were closed. It was still easy to hear the direction BUT harder to hear the location in depth.When the tef measurements got to where it looked like one driver, the effect was stronger still.
This was an irrelevant thing for 99% of where the horns are used at work however I used them at home and the effect on the stereo image was dramatic.
When a loudspeaker provides a depth position que, then this detract from the stereo image. In that case (as most speaker do) when you play a mono signal which should be a single apparent source dead center, there are two additional sources” you hear in the physical depth of the speakers. If a speaker doesn’t radiate a complex field, then your brain hears the sources less and the phantom more.
Now what kinds of sources do this?A number of hifi speakers have heard radiate only a small source identity, A Quad esl-63, a Manger on a flat baffle and to a degree some small loudspeakers where the drivers are small and close together . A hifi company has recently discovered the audibility of source identity also, google up the KEF blade concept designed around that criteria..
What radiates the identity i think is a complex field, one that provides ample clues in the differences between the right and left ear inputs. Many aspects can cause that too.
If what arrives to the R&L ears from one speaker is identical, there is no source distance information conveyed and if part of a stereo, the sources disappear into the image to a much larger degree. For a mono phantom, you do not want a Right, Left and Center sounding image.For the skeptical, consider an experiment. Obtain a pair of small fostex full range drivers. These are necessarily limited at either end BUT if mounted on a large flat baffle, radiate as a simple source up to reasonably high frequencies. .
Move these away from the walls in the room and listen to the stereo image, these can be stunning in the depth and “real” feel of it (if present in the recordings).Part B is the capture.
This is where it really falls flat, most recordings are not a capture of then event but a re-creation of one in the studio. You can only hear how far it falls flat when you hear something more realistic. As we hear in 3d but measure from one point in space, one can make a recording of a loudspeaker and “hear” what it sounds like without the 3d brain processing.
We used generation loss recording of speakers in the early days as a reality check. I think people would be amazed, stunned and befuddled how very few generations a loudspeaker can be used in a closed loop audition where a truly faithful device has no limit.A really good microphone can be much more precise than any loudspeaker because of it’s dimensions and power flow amount and direction. If you use a measurement mic to make mono recordings, they can be chilling in their realism and better yet, you were there live so you have a big edge over someone else’s recordings.
The problem is you cannot easily record a live stereo image with two mics, there is no simple combination of spacing etc that “captures” the event and so most of what we hear was created with pan pots etc in the studio.I have an approach to the issue too, while it has been a back burner project, I believe this approach is more like the idea behind a hologram although not being a massively parallel system. This works in a 360 degree capture although that requires 5 channels, 8 to cover the “up” direction too.
Pop on some headphones and try a couple of these recordings. Not the most exciting stuff but the setup is cumbersome and ugly right now and for me environmental sounds have the advantage that I know exactly what it sounded like and they are usually available. Also, these have no compression so they sound quiet and the fireworks will severely tax nearly any loudspeakers, is ruined by the mp3 process.
Try with good headphones first, FWIW, these are only the front two channels about the width of your vision.
Recordings at the bottom of this page;http://www.danleysoundlabs.com/technical%20downloads.html
Best,
Tom Danley
Danley Sound Labs
Edits: 05/20/12Follow Ups:
"The problem is you cannot easily record a live stereo image with two mics, there is no simple combination of spacing etc that "captures" the event and so most of what we hear was created with pan pots etc in the studio."
I've been a believer in this all along!
Cheers,
Presto
"The problem is you cannot easily record a live stereo image with two mics"
This can work just fine, assuming good acoustics, engineering and musicians. The Water Lily Acoustic orchestral recordings of Mahler's Fifth and Shostakovich's seventh symphonies are excellent examples of this.
On a smaller scale some of the Chesky jazz recordings have very natural stereo and were made with one stereo microphone.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Hi Tony
This is a topic I love!
It is true, if you take two microphones there is no combination of spacing that permits the genuine item to be captured accurately.
The Blumein technique comes a lot closer, it is a special case of two vertically stacked elements (with open backs usually) and unlike a simple pressure mic have a figure 8 pattern.
This does two important things, one, it is “mono compatible”, a single sound source produces the same signal phase / time on both mics.
This means you can sum them and not have all kinds of comb filtering that is present when you sum two or more mic signals that are in separate locations. In the horizontal plane, they are in the same location in time.
Two, the figure 8 pattern provides amplitude shading according to horizontal angle and this is why a signal to the left is louder on the left channel. Two pressure microphones in very close proximity produce the same signal but have no directional discrimination.
The weakness in that design is that that each mic has a figure 8 pattern while what you would like to capture is only what is in front, not the rear. Also, the shape of the figure 8 only allows a fixed degree of amplitude shading vs angle and so is limited to a two channel system as is used currently. Cardioid mics can be satisfying but their patterns change a lot vs frequency.
The microphone array thing I am working on is along this line but done an entirely different way.
It allows the sound to be detected as if it were from one point in space but can be divided into a large number of channels if needed.
Also, where the Blumein is not coincident in the vertical plane, this can be made to capture a full hemisphere from one point in space.
As you enjoy “stereo” image, please pop on a set of headphones and try a couple of the recordings they put on the web site at work.
These have no compression so you may have to turn the volume up to get to a real sounding level. Try the Harley or Trains and keep in mind this is a work in progress and only the front image, more or less the width of your vision.
Let me know what you think.
Best,
Tom
Recordings at bottom of the page;
http://www.danleysoundlabs.com/technical%20downloads.html
could also be used for recording, and reproduction. Onfotunately the standard array mics are a little noisy for music recording and a high quality low noise microphone would e costprohibitive at Qty 90.
And yes Blumein array is -IMO a nice recording technique - especially useful for the ambience feed to a recording or medium sized live events in the somewhat near field. A second (or 3rd) X-Y array can be used with appropriate delays to mix in ambience from the rear of the hall. For engineered recordings, M-S mic configurations for the individual performers and instruments are great - you can "place" the track anywhere adjusting the levles and delays relative to other tracks and the mix down to Mono is honest.
Three most important things in Audio reproduction: Keep the noise levels low, the power high and the room diffuse.
ABOVE is a reference to Belafonte at Carnege Hall... As being a stereo recording... IT IS NOT and the photos at the performance shows that,,, Harry is holding one mic and walking back and fort on stage,,,His band has two mics close to the floor not even matched spaced a couple of feet apart... Two other mics above his head are faceing away from his body tward the back of the stage,, A string section is grouped in another position on stage,,, NO imageing is produced,,,Also WHAT IS MOST INTERESTING ALL APPLAUSE SEEMS TO COME FROM THE FRONT ON STAGE WITH BELAFONTE,,...
about the applause coming from the front? You just pointed out how the mikes were placed. If they were cardioid types, that is to be expected.
Stu
The mics in the Belafonte concert are not pointed at the audience,,So how did the audience appear in front of you in reproduceing the mix of the recording.. When Belafonte asks the sections of the audience to respond,,Why did the section NOT give proper locolazation cues on the record ??
mountains of molehills.
If the mikes are omnis then the phenomenon you mention has an obvious explanation.
If the mikes are your typical cardiod pattern, which is a heart shaped pattern with the indentation being at the mike, you are capturing the sound off the sides and slightly to the rear.
Now take applause: can you identify individual people clapping? I don't think so. Applause is basically random noise and it literally echoes off the sides of the venure. Directionality concerning applause is basically impossible, not to mention that you have tremendous issues with phase, particularly wince applause tends to have severe "bounce" off side walls.
A normal mike will pick up a lot of the applause as it echoes off the side walls and the reflectors over the performers. The mike can not distinguish individual people clapping ( at lest for normal clapping) and so your ears perceive the clapping as being being all around.
Next time, try standing on a stage while the audience is clapping. The sound completely engulfs you, even if you are on stage.
If you want to hear applause as it should try a discreet four channel recording, like Kimber's Iso mike recordings.
Stu
The mics are in the photos and the manufacture can be identified..plus what way they are pointed,,So STEREO claimes are false....BELAFONTE is Obviously MONO..
All stereo recordings employ at least two mikes. What's wrong with more and then having to mix them down?
In a live performance, you can't have just two fixed mikes as the solo performer is moving around on stage. It isn't a studio. Concessions must be made to accommodate the performance.
Stu
There is a mono version of Belafonte at Carnegie Hall, but the stereo version actually is stereo, as in RCA Living Stereo.
Yes I know that...I have both,, But it does not answere my question.. RCA is pulling the wool over your eyes claiming a full stereo recording,,When on stage,,A full stereo mic setup did not exhist,,
The sound out the back of the figure 8's can be a benefit, as it provides hall ambiance. If this proves excessive, the microphones can usually be moved closer.
The big downside of minimal microphones is that the musicians are responsible for the balance and it won't be easy to fix their mistakes. It will be impossible to "Autotune" bad vocalists, but that's a good feature, IMO :-)
Comb filtering is a big problem when spatially separated microphones are mixed into a single channel. It is less of a problem when each microphone has its own speaker, as the ear hears these two cases differently at high frequencies.
My late wife loved your "Train Start" recording. I will listen to the newer ones when I get the chance. But it will be on speakers, as I don't have any decent headphones, just a handset that I use for Skype.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
5 - 8 channels. Um. Yeah. Sure. Great!
“5 - 8 channels. Um. Yeah. Sure. Great!”
Not sure if you actually tried it, but put on headphones and play the recordings at the bottom of this page.
http://www.danleysoundlabs.com/technical%20downloads.html
Hopefully, these (the stereo image) will sound unusual to you but those are the front two channels more or less the width of your vision.
With the right speakers, you can reproduce this in a living room.
With 3 more channels, on can capture a 360 degree view of the sound field or with 8 a full hemisphere. The effect is pretty cool actually, it sounds like you are somewhere else.
Best,
Tom Danley
I couldn't get the link to work, it just takes me to the home page.
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