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Discussion in 'Electronic Repair' started by Phoena, May 25, 2013.

  1. Smarty

    Smarty Guest

    I too have been very impressed with binaural sound, and for a time
    actually carried a portable Sony DAT recorder with microphones designed
    to be worn in my ears, thereby capturing the precise signal structure my
    ears and brain had learned over time to make direction of arrival
    decisions. I recorded a number of live performances as well as a lot of
    ambient daily activities, and the playback was as faithful and authentic
    with regard to the original as any "high fidelity" scheme I have
    encountered in my entire life including that from some audio systems I
    have owned which cost many tens of thousands of dollars.

    Stax has released a wonderful collection of binaural recordings on CD,
    many of which I own, and other occasional binaural recordings are out
    there from other labels as well. These have been recorded with a
    mannikin dummy head which diminishes the accuracy and richness of the 3
    dimensional experience somewhat compared to custom miked content, but
    they are still very engaging and very much an improvement over stereo.
    Unlike normal stereo headphones which present an image essentially
    inside the head, these recordings open up the 3D space profoundly, even
    if your earphones are small buds inserted in the ear canals.

    You can be very proud of your grandad. I have tried to show my
    grandchildren some examples of what I have done in my engineering
    career, and, for the time being, they remain unimpressed.....!
     
  2. Smarty

    Smarty Guest

    Absolutely wrong answer! It most assuredly does violate both
    mathematical and physical constraints. You might want to take a look at
    the Ambisonics website where they state:

    Matrix quad tried to get the four
    original channels into two and back again,
    which is impossible. A sound panned
    around the control room in a circle (black)
    would be replayed as a flat ellipse by SQ"

    The flat ellipse shown in the Ambisonics reference is a typical result
    of using a matrix approach, and other matrix designs have other odd
    shapes, the Sansui QS matrix resulting in a heart-shaped / cardioid
    sound field. In any such example for any choice of matrix coefficients,
    the same result occurs, namely, the original directionality is lost, and
    the sound field changes its shape with frequency. In Sansui's design
    (later adopted for theater use as well) the rear channels effectively
    produce a single centered rear channel at the acute vertex of the
    cardioid. The brain and ear don't get any right rear to left rear
    directionality whatsoever. In the SQ matrix, there is very little front
    to back discrimination, with the virtual sound sources placed almost
    entirely to the left and right of the listener, imitating spatial depth
    by widening the front and adding hints to the rear.

    Both are entirely avoided using discrete analog techniques of the
    1960s, as in ***4 DISCRETE CHANNELS***. The matrix methods are synthetic
    in that they synthesize an approximation to the discrete wavefronts,
    good enough to fool the majority of listeners, but by no means accurate
    or complete.


    http://www.ambisonic.net/pdf/ambidvd2001.pdf as well as the surrounding
    articles and introduction page for the Ambisonics approach.
     
  3. "Smarty" wrote in message
    We have the problem of two people who agree, arguing over the agreement.

    That's what I said. Please re-read what I posted.

    I'll repeat it, though. In a matrixed quad system, a properly designed decoder
    can completely isolate one or two channels, when they are the only active
    channels. That is what I said, and I stand by it. (To put it mathematically --
    you can solve for two unknowns -- but no more -- when you have two equations.)

    These is easily demonstrated with a single channel on a test disk, or by
    playing a conventional stereo recording through an advanced SQ decoder.
    Nothing comes out of the rear speakers.

    They can, under the conditions previously stated.

    The advanced SQ and QS decoders do not use "gated" amplifiers, which had been
    abandoned years earlier. I owned such a decoder (the Sony SQD-2020), and it
    sounded terrible, because it shut off channels with important material.


    I'm going to stop at this point and simply state -- in an objective and
    non-personal matter -- that you aren't familiar with how matrix and decoding
    work. I wish I had some material to offer, but a lot of my source material has
    been lost or misplaced over the years. If you'd to discuss this over the
    weekend, we can get together on the phone.
     
  4. In fact, an SQ system could not localize a left-rear-only signal nor
    Absolutely wrong answer! It most assuredly does violate both
    mathematical and physical constraints. You might want to take a look at
    the Ambisonics website where they state:

    Matrix quad tried to get the four
    original channels into two and back again,
    which is impossible. A sound panned
    around the control room in a circle (black)
    would be replayed as a flat ellipse by SQ"

    READ WHAT I SAID, rather than what you think I said.
     
  5. Smarty

    Smarty Guest

    I will begin with your last and most offensive comment first. I am not
    at liberty to describe this in detail given certain non disclosure
    agreements, but I will leave you with the opportunity to research Peter
    Scheiber and the patent rights sold to Dolby for the design and
    implementation of original matrixing audio technology ultimately sold to
    Columbia to become SQ. I can only state a single comment, which is that
    Mr. Scheiber, a musician, and non engineer, holds the original patent,
    but relied on a certain graduate university student to develop and build
    his design concept. I will leave it to your fertile and most ad hominem
    imagination to figure out who that graduate student was. And I will
    remind you of my original introduction to this topic earlier in this
    very same thread by stating that I had first worked in Toronto on a
    matrixing audio encoder design for theater use starting in the 1960s.

    Since you have already amply demonstrated an exquisite knack for putting
    two and two together and getting two, I will now briefly summarize your
    conclusion that we are supposedly violently agreeing upon.

    If you are now stating that a 4 channel matrixing encode and decode
    system can merely handle two channels at a time, then you are now
    beginning to demonstrate and acknowledge their fundamental inability to
    extract and isolate 4 channels independently. If you are somehow trying
    to assert that by only doing two channels at a time, they somehow
    preserve these 2 channels correctly in the presence of any other energy
    arising from the other two channels whatsoever, you are utterly wrong.

    The point of this is that given a 4 channel input, the very best you can
    ever hope for are 4 poor imitations of the original 4 discrete signals.
    If you are somehow arguing that the method succeeds with simultaneous 4
    channel input, you are incorrect. This type of solution is referred to
    by engineers as synthetic, since it uses a synthesis method to form
    approximations of actual things. Think "Moog synthesizer" if you cannot
    grasp the meaning in a more expansive way.

    I have merely stated that such systems as we have been discussing are
    "synthetic" and the notion that they somehow isolate and extract is
    technically wrong.
     
  6. Was "surround" at the time a true 4 channel recording?
    Out of these devices, which did true decoding of extra channels out of a a
    two channel recording?

    How did the encoded recordings sound if you skipped the decoders? With old
    tape decks and Dolby noise reduction, it didn't matter on playback.
    unless all your recordings are only available in plain stereo.

    I actually had a really hard time locating a surround sound audio test
    file to use with a WD Live video/audio playing device. My surround decoder
    has the generate noise on each channel test for setting up speakers, but
    that doesn't tell you if it really understands the signals coming out of
    the modern media player.
     
  7. Ah- SQ.

    I've always wondered what that was. I seem to think I've seen that on
    laserdiscs, and just checked mine, but none have it, not that I'd be able
    to play it back correctly anyways.
     
  8. "Cydrome Leader" wrote in message
    I'm not sure what you mean by "true". Matrixed recordings were considered
    four-channel recordings.

    The first modern surround recordings came from AR/Vanguard. They were called
    "surround stereo", I believe. After that, the term "quadraphonic" was adapted.
    (And please don't complain about mixing Greek and Latin. "Dinosaur" is a
    similar hybrid.)

    Strictly speaking, none of them, as two-channel recordings, by definition, do
    not have extra channels to be decoded.

    However, some of the devices -- such as the Space & Image Composer and the
    Ambisonic decoders -- could manipulate 2-channel recordings to wrap the sound
    around you, or extract ambience, or both at the same time.

    Generally, they sounded pretty much like regular stereo. The rear channels
    weren't lost or diminished in level -- they simply appeared in the front.
    (With SQ recordings, LR and RR often appeared slightly "outside" the front
    speakers.) Unfortunately, recordings with ambience in the rear channels tended
    to sound overly reverberant in stereo. EMI was obliged to reduce the ambience
    levels.

    Not at all. Your control unit probably has surround modes to enhance stereo
    recordings. And hall synthesizers can be bought on eBay.

    If the program source is "discrete", then there shouldn't be a problem. *

    Matrixed material generally requires manual mode selection. Lossy-compressed
    materials (such as the various Dolby Digital formats) are //supposed// to be
    correctly recognized by your control unit. Regardless, if playback doesn't
    seem correct, try forcing the controller to different modes (if it allows
    this). I agree that a test disk would be useful.

    * With one exception. Some Blu-ray players won't properly output channels 6
    and 7 unless you change one of the player's default settings.
     
  9. "Cydrome Leader" wrote in message
    The explanation given was almost completely incorrect.
     
  10. This may sound weird, but I'm against meddling with recordings and using
    weird made-up affect that have nothing to do with the original recording.
    If it wasn't in the recording, I don't want to hear it. Not everything was
    recorded in a cathedral either. If I can hear the strange defects in a
    recording as it was made and mixed, that's plenty exciting for me.

    Again, this all depends on the type of music as well. Wether or not
    heavily produced studio recording from Yes sounds better in a "concert
    hall" or "jazz club" setting is questionable.
    I had to screw with all the settings for type of sourround signals and
    how they were outputted (hdmi/toslink or both) and what format and
    compatibility modes to output to the decoder. The decoder only has a few
    vague settings. Eventually it all worked, but the bluray player needed
    firmware updates.
     
  11. The explanation for SQ was wrong?
     
  12. "Cydrome Leader" wrote in message
    That's not weird. Over the years I've learned that most "enhancements" do
    nothing to truly improve the sound. Worse, the better the playback equipment,
    the more the enhancements become audible as unmusical changes.

    Of course, two-channel recording is fundamentally limited in its ability to
    convey directionality and spatiality. This might not be important if you're
    listening to multi-miked studio recordings, but it /is/ important when the
    music was (or should have been) recorded in an appropriate acoustic space.

    The Carver Sonic Hologram actually does work -- at least with simply-miked
    recordings. (I've had little experience with other crosstalk cancellers, which
    might or might not work.) An Ambisonic decoder can "extract" the ambience from
    a well-made recording and present it in a very natural-sounding manner.

    Of course, such devices require sending the program through a processor, which
    to an audiophile is generally a no-no. That's the beauty of a hall
    synthesizer -- the generated ambience is played through four additional
    speakers, and the original recording is left untouched.

    That's not surprising. Consumer photographic and electronics products have
    become incredibly complex, and the idiots (I use the word deliberately,
    because they are idiots) who write the user manuals neither understand the
    products nor how to explain their use to the reader. I have long considered
    starting a class-action suit against the major manufacturers for their lousy
    manuals.
     
  13. "Cydrome Leader" wrote in message
    Yes. Smarty's explanation is based on a misunderstanding of the Scheiber
    patents (which I looked at last night). And while we're at it, neither SQ nor
    QS is derived from nor dependent on the Scheiber patents.
     
  14. "Smarty" wrote in message
    You have picked The Wrong Person to attack on knowledge of surround sound.

    I am a degreed EE, and a member of Tau Beta Pi and Eta Kappa Nu. I used to
    make live recordings (stereo, quad, and Ambisonic), and have rubbed noses with
    a few (not many) movers and shakers in the audio industry. At one time I was
    the only audiophile reviewer who took surround sound seriously.

    I don't remember a patent dispute, but I've no doubt there was one. The
    problem is that the Scheiber patent is for a fairly crude quad system, and
    there is nothing //fundamentally// innovative about it that would allow it to
    have, shall we say, a "controlling interest" in SQ or QS.

    That's hardly surprising. Though Scheiber's patents are pretty much valid, the
    American patent system has long been a mess, with people winning suits based
    on completely invalid patents. (The patent for intermittent wipers is a
    classic example.)

    I used to get the JAES. (I'm still a member, though I haven't paid dues in
    years. Saul Marantz and Jon Dahlquist supported my membership.) My favorite
    part of the magazine was George Augspurger's trashing of "new" audio patents.

    What is [the] truth?

    You mean you don't like being told you're... mistaken.

    Quad Bob is an acquaintance, whom I've not spoken with in several years.

    If Peter Scheiber invented the SQ encoding system that Ben Bauer so vigorously
    promoted -- that's news to me. His patent

    https://www.google.com/patents/US3632886?printsec=abstract#v=onepage&q&f=false

    misses an important element of SQ, QS, and Ambisonic UHJ encoding --
    quadrature phase shift. If I recall correctly, this shift reduces or removes
    ambiguity between front and back signals.

    I checked the "Quadraphony" collection from the AES, published in 1975. It is
    not comprehensive, of course, but it contains nothing from Peter Scheiber that
    even remotely suggests SQ. If such exists, please provide a reference or send
    a copy.
     
  15. Smarty

    Smarty Guest

    My incredulous reaction:

    Is it even slightly possible that William, claiming to be a graduate
    E.E., (member of Tau Beta Pi* and Eta Kappa Mu honor societies no less),
    is capable of actually believing that:

    1. trying to encode 4 separate audio channels into a 2 channel standard
    vinyl LP system and adding 90 degree quadrature phase shifts could
    possibly "remove the ambiguity between the front and back signals" ??

    2. "Whether purity is good or bad, the electron beams have to land
    /somewhere/. In a B&W image, it might not matter much if red winds up on
    blue, blue on green, and green on red. The result will be /something/
    approximating a shade of gray. "

    These are not the logical or technically insightful comments of a
    degreed E.E. regardless of claimed honor society memberships.

    These are the statements of someone who does not understand how either
    audio channels or CRTs work.

    Might I ask you to explain, for example, how putting a 90 degree phase
    shift onto any of this audio would remove the ambiguity of front versus
    back? And yes, I am aware that some but not all of the competing matrix
    schemes using +/- 90 degree phase shifters in the rear made such
    specious claims.

    You may know how to read and quote others, but I would LOVE to hear you
    explain technically how either of your hair-brained interpretations
    ACTUALLY WORK from an engineering perspective. Any legitimate engineer
    who knows these topics correctly could NEVER BUY INTO THIS BULLSHIT.

    *I was a member of Tau Beta Pi and shudder to think that other members
    of this prestigious society could be so entirely clueless. I also am
    surprised you are not or were not a member of the I.E.E.E. I was a
    Senior Member for many years and began as a student member over 50 years
    ago. Like the AMA for physicians and the ABA for attorneys, it is the
    defacto professional organization for those who are real graduate E.E.s,
    with over 400,000 members currently.
     
  16. Smarty

    Smarty Guest

    William, recall from modulation and estimation theory and Fourier
    analysis that quadrature modulation //DEMANDS A CLOCK//, or must have an
    ability to self clock. Neither of these exist in a compatible 2 channel
    analog system of this type, and adding such a clock eliminates
    compatibility with the entire world of analog playback systems. I will
    assume you were not ascribing the design to this approach.

    And of course the simple act of putting a 90 degree phase shifter into
    the rear audio paths does NOT make their resulting signal quadrature
    modulated. It bears no resemblance to the more widely understood I and Q
    quadrature method used in many places including color TV to truly carry
    independent data. It merely corresponds to a quarter of a wavelength
    shift to the one and only amplitude conveyed by a singular waveform.
    Even with careful microphone choices and placements along with a mixing
    and recording chain which preserves phase integrity, the very best
    outcome one can hope for is a third derived phantom source centered in
    the rear, as was well demonstrated earlier by Hafler as well as some of
    the 1960s Delco radio designs which ran L-R across the rear speakers in
    a few cars. Given the signalling and compatibility requirements,
    creating a rear center signal only was / is unachievable without also
    forming front artifacts of a substantial nature.

    As regards Scheiber:

    Scheiber's original patent was in the 1960s. CBS did not file until the
    early 70s, and their lawyers were appropriately committed to avoid
    infringement issues, something that Peter very well understood and
    capitalized upon. His approach was important only in that it came first.

    Scheiber's method for producing 'surround sound' was neither superior
    nor especially innovative, since all such techniques relied on an
    incomplete / impossible technical foundation which could never deliver 4
    separate channels at a time, nor could they 'isolate' nor 'extract'
    information exclusively to a given channel while other channels were
    present except in special cases. These special cases they naturally
    demonstrated and portrayed as successful solutions. Putting designs
    together which "worked" was not the problem; rather, the choice of
    design parameters boiled down to those which appeared to interfere
    least, and whose effects were dramatic without being exaggerated, a
    compromise which is actually hard to achieve given the limit of 2
    channels to work with. He and all the other contenders metaphorically
    offered their recipes to put multiple ingredients into a stirred pot,
    and then showed how they could, for some of the ingredients, some of the
    time, recover individual ingredients.

    Since the patent office and the courts award great benefits to 'prior
    art', and since the matrixing approaches all were merely artistic
    concoctions of time delays, phase shifts, gain controls, and their
    associated time constant choices, the fact that one system might
    actually sound better under some conditions but worse under others was
    not a legal battle but a marketing battle. The legal battle was to
    essentially avoid and if possible totally prevent infringement lawsuits,
    which was both Columbia's and Dolby's primary objective. He wound up
    with the credit for the "discovery" and was financially rewarded, but
    never for selling a single encoder or decoder. His genius was really in
    getting to the patent office first with a working prototype to
    demonstrate proof of concept. For me it was an exciting time and the
    first glimpse for me of the business side of electronics.
     
  17. To "Smarty"...

    I could go on for several pages, but will limit myself. I //could// sum up
    this entire exchange by saying that I feel like Gus arguing with Woodrow, but
    other things need saying.

    Several months ago I called David Janszen (the son of the late/great Arthur
    Janszen) to ask about the modeling of planar radiators. He told me that the
    analysis was rather more complex than I'd imagined, and referred me to Olsen.

    Did I criticize him? Did I tell he didn't know what he was talking about? No.
    I got a copy of Olsen, and though I haven't had time to study the appropriate
    sections, I will eventually get to it. (There's a lot of material on acoustics
    I've never fully understood, so it's worth reading for that, alone.) Now...
    Even if David Janszen weren't an authority in speaker design -- even if he'd
    been someone I'd never even heard of -- I would have taken his response
    seriously.

    There's nothing wrong with assuming that "some guy you've never heard of"
    might -- just might -- know something you don't know. If he doesn't, you'll
    eventually find out.

    There's a difference between knowing and understanding. It's not enough to
    know the facts. Understanding requires the mental effort to "wrap your head
    around" a concept and make it your own. I like to say that if you can't
    explain something (in relatively simple terms), you don't really understand it
    yourself.

    Unfortunately, too many people believe what they're told -- even when it's
    dead wrong -- then try to defend their beliefs against rational -- or just
    common-sense -- attack. (I have engaged in some of the most appalling
    arguments here and elsewhere over people's misconceptions about digital
    processing. I've also learned a few things in the process.)

    Here again are the two patents I referred to.

    https://www.google.com/patents/US3632886 (click on Abstract)

    https://www.google.com/patents/US39...a=X&ei=47isUYfwOeP-igKhnoHIDg&ved=0CFMQ6AEwBA

    Please at least browse them. If you have questions, ask and I will try to
    answer them (though I don't have detailed knowledge of every aspect of
    matrixed surround).
     
  18. "Smarty" wrote in message On 6/3/2013 7:15 PM, William Sommerwerck wrote:

    Because the following comments are so ad-hominem, they require a response.
    Read the patents.

    2. "Whether purity is good or bad, the electron beams have to land
    /somewhere/. In a B&W image, it might not matter much if red winds
    up on blue, blue on green, and green on red. The result will be
    /something/ approximating a shade of gray."
    In fact, Arfa said the same thing. But you didn't attack him, because you
    perceive him as an expert.

    Hair-brained? You mean hare-brained.

    You are criticizing something you don't understand, that you have rejected
    without consideration.

    No comment.

    One merely buys one's way into the IEEE. It is not honorary.

    You don't have to be a graduate EE to join. I entered as an undergraduate,
    around 1967 (which is pushing 50 years), and remember a special issue on the
    Fast Fourier Transform, which was then coming into common use.
     
  19. Smarty

    Smarty Guest

    Precisely! This was the reason I asked you to explain why / how you
    could make the statement that a 90 degree phase shift added to the rear
    discrete audio channels in any encoder which mixes down to 2 channels,
    to use your exact words, "removes ambiguity between front and back
    signals". Again, to borrow your exact words, "If you can't explain
    something (in relatively simple terms), you don't really understand it
    yourself".
    I am extremely familiar with Scheiber's work and resulting patent, which
    I read in various stages of its submission, and have certainly more than
    'browsed' Bauer's patent and several others when they were issued. I
    thank you for the opportunity to ask you any questions, and will, once
    again ask you the simple question:

    Why did you make the statement that a 90 degree phase shift added to the
    rear discrete audio channels in any encoder which mixes down to 2
    channels, to use your exact words, "removes ambiguity between front and
    back signals" ?

    Forgive my skepticism and my continuing disrespectful tone. If we were
    both automotive engineers, and you made a statement that the anti
    gravity feature of your engine provided enhanced gas mileage, I would
    initiate the same type of request for clarification. Those who
    understand modulation theory and these specific types of surround sound
    devices would never make such a statement, and I am merely asking you to
    explain how such an outcome could occur.
     
  20. Smarty

    Smarty Guest

    When I was in graduate school and earning a bit of extra income as a
    teaching assistant, I genuinely feared being asked questions in front of
    a group of people by younger students and not knowing the answer. The
    natural and safe way to deal with all such situations was to reply to
    the inquisitive student:

    "Read the textbook"
    Hardly, I perceive him as a very knowledgeable repair technician with
    vast experience who may or may not have the understanding of the
    underlying physical details of how things work in this specific area. If
    I were to ask him, or you, or others on this forum a question like:

    "Why isn't a pure white raster the outcome of mis-registered set of
    beams, given that it supposedly does not matter where the beams land?",
    he may be as clueless as I am.
    Absolutely true, and as I mentioned in my prior reply, I too joined as a
    student, quite a few years before you, and actually do remember the
    'discovery' of the FFT in that same time period.
     
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