|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
63.111.2.217
In Reply to: RE: Real vs Reproduced posted by Inmate51 on August 20, 2014 at 20:12:34
The answer is incredibly easy - take a very simple case, A single Cello playing in a room for you. (My Niece was just in a recital this past weekend.) The sounds produced by the cello emanate form all over instrument - the front, the back, the bridge, & strings, of course.
The acoustics radiate outward into the room - are reflected by the various surfaces and combine in a completely non phase coherent way at your ears. Then the fun stuff happens. Your ears convert the waveform into a arbitrarily sampled god-zillion different neural impulses - that combined with visual clues - assuming your eyes are open - that the brain processes into an event that moves us with the emotion in the music and the real time experience of the performance.
In stereo (or multi-channel) reproduction the waveforms from pressure variations in the room are recorded mostly with directional microphones (omni's would be better perhaps - another discussion) at discrete positions in the room. In the production - those signals are blended into the two or more signals making up the recording. Heyser called this process "Apodization" - literally "Removing the Foot" - or foundation of the live event.
In playback, we take those two somewhat correlated voltage signals, amplify them without too much alteration, directed then to some kind of loudspeaker that further distorts the signal - in space, time and frequency. By the time it begins producing its pressure variations into a room with a completely different characterization (visually and acoustically), there is absolutely very little resemblance to any of the recorded tracks - let alone the waveform of pressure variations that occurred at your ears.
We sit in out listening chair - perhaps to a Klipschorn or WATT or Quad, or 35 year old twice re-coned Advent - and our brain works the magic, trying, and often succeeding to fool us into imagining a live performance.
It is a miracle it works at all...
Three most important things in Audio reproduction: Keep the noise levels low, the power high and the room diffuse.
Follow Ups:
One of the barriers to getting the real thing are removed. I did several recordings of solo violin with the violinist standing between my 8 foot tall Acoustats and the microphone at the listening position. Other than the overly dry room acoustic (you get the same room twice) I was able to get a very convincing reproduction when played back through the Acoustats (recording was made on a TEAC R2R analog recorder). Naturally, the Acoustats, being a full range electrostat, were time coherent.
Spaced omni microphones in a decent recording studio - supplemented by some near field M-S oriented mics near piano and other percussion that can be spaced and time aligned with the omni-mains. Gives you the best ability to decode a relevant waveform reference, and maintain the ability to steer (somewhat rationally) signals and ambiance into the production.
Then a time coherent loudspeaker at least in the 250-3000 Hz range - provided 1st reflection energy is down 10dB or so - can give you a somewhat decent wave form on the reproduction side.
What is really interesting though is all that seems to not really be necessary for the illusion to congeal in our minds. Since the majority of recordings are not made with that in mind, and even some of the most recommended audiophile recordings are engineers creations of events and performances recorded in various times and places, we can throw out that requirement. And likewise the need for time aligned loudspeakers. Yes they are magic, my first listen to ESL57, Vandersteen 2C, DQ10 all threw the "image" easily - but so do my MMG's and my old Advents.
Although, there is one aspect of sound reproduction systems that is critical AND required: You have to have confidence that the system will do it! That is why I think we fall into a bit of "snobishness" here in the Asylum. If you've invested time and more time into your own system - critically listening, and you move to a lesser system, for example - a MP3 data stream, bluetoothed into a sound bar. You probably won't hear the magic. But another listener just might!
Over the years I've sold and/or set up 100's of systems for folks - and I can pretty much guaranty with the right recording it will be perceived as "real" by the owners - with just a few exceptions. Sometimes it just setting the stage for them. Other times just balancing the system with instrumentation, builds that level of confidence.
"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius
For about 2 years I tried going back to speakers that were not time coherent and in the end I had to go back to the coherence that does a more thorough job of convincing me of a live event. This is particularly true with good live recordings of which I have several.
I have heard experiments where otherwise decent speakers were made time coherent digitally...without any manipulation of the frequency response and the improvement by making them time coherent was nothing short of stunning. It seems to me that while your brain is cleaning up the mess speakers make it is working awfully hard to do it and this leads ultimately to fatigue and less feeling of real.
It is also in the end I had to come back to single ended amplifiers...I can hear the discontinuity of a push pull amp. Not at first mind you but after living with it for a few months I knew the two I tried had to go and come back to single ended amps (I tried the Einstein "The Absolute Tune" and the VAC Renaissance 30/30...both excellent machines but not as coherent as a good SET).
It's even more complicated and interesting. For each note that your cello plays, the strings and the various wood panels of the instrument establish unique vibrational patterns (modes) which propagate into the air and away from the instrument in 3D space. These sound waves interact (constructive/destructive interference) to differing degrees as you vary distance and direction away from the instrument (see Science, vol 310, pp 1414-1415, December 2, 2005). Thus the sound of a single instrument depends on 3D angle and distance.
Add reflections (and partial absorption) from surrounding objects and it gets even more interesting. There is complexity and richness in the real thing that no system in a home can reproduce.
On the other hand, when I listen to my rig I don't hear a lot of coughing or rattling of programs, and it's (sort of) like I'm sitting in a really good seat (and I can hit "Pause" when I need to go to the bathroom).
Yes! Absolutely!
You get it!
:)
Your brain works a lot harder when listening to reproduced music vs. live music. (EEG studies) Logic says it has to fill in the gaps...
Three most important things in Audio reproduction: Keep the noise levels low, the power high and the room diffuse.
Hey, you already wrote that in another thread.
;)
yeah - here is was a more appropriate answer....
At least I was stealing it from myself! no plagiarizing here.
Three most important things in Audio reproduction: Keep the noise levels low, the power high and the room diffuse.
My subject is the most important thought to me.
"This is Your Brain on Music" by Levitin
Three most important things in Audio reproduction: Keep the noise levels low, the power high and the room diffuse.
Thanks, I'll look into that!Most of the texts I have are now classics and no longer available -
"Acoustical Engineering" by Olson,
"Music, Physics and Engineering" also by Olson and still available,
"Music, Acoustics & Architecture" by Beranek,
"Acoustical Designing in Architecture" by Knudsen and Harris,
"The Technique of the Sound Studio" by Nisbett,
"The Audio Cyclopedia" by Tremaine,
"Architectural Acoustics" by Lawrence.While the equipment examples are clearly dated, the information remains pertinent. More recent texts present newer examples, but follow the same informational pathes. For example, "Master Handbook of Acoustics" by Everest. "The Loudspeaker Design Cookbook" by Dickason is great. But my new fave recent book is "Why You Hear What You Hear" by Heller. It's a fascinating and well-written work. My minimum recommendations for every audiophile (and professional, for that matter) are:
"Master Handbook of Acoustics" by Everest,
"Music, Physics and Engineering" by Olson,
"Why You Hear What You Hear" by Heller.Those three books should be on everyone's shelf.
Edit: Fixed a name. It's Heller, not Geller. Geller is a local orthodontist. Sorry!
:)
Edits: 08/22/14 08/22/14 08/22/14
.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: