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  1. #1

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    Default Lets talk freq response....lp vs cd

    Ok, I am not quite sure how to put all this down, my mind is spinning today, so stay with me:

    CD's are limited to what 20KHz? Most CD's don't have much over 15KHz? Records (vinyl) can reach out to 25Khz and beyond....
    Some Stylus LP cartridges reach out to 50Khz.....

    Musicians, heads up, lets add harmonics/supersonics into the discussion too. Supposedly, take a 21K and 23K sine tone, you can't actually hear it, but the 2K 'beat' it produces is audible?

    Do some instruments reach out farther than we can hear, but produce this 'harmonic' or 'beat' at lower frequencies that we CAN hear? (I'm just learning harmonics on my bass)

    I have always felt that LP's had a warmth to them, is this what I am hearing? Is the cd format really limited to 20Khz? How does the range of amp figure in, if it is 20 to 20, does it even matter what the source can do?

    AND

    (per a paragraph at ohmspeakers.com) Most males over 30 can't hear as high as 20Khz. Some say as low as 17Khz. Throw that into the equation, if it holds true.....

    Thoughts gentleman?

    Russ
    Last edited by RuSsMaN; 09-28-2001 at 11:04 AM.
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.

  2. #2

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    Default No frequncy response problems w/ CD's

    RuSsMaN,

    I believe the frequency response of CD's isn't necessarily the problem. I image that one could put whatever frequency of information on they wished, as long you had the software and hardware to deal with it and recognize this info. Also keep in mind the regardless of the frequncy, All that is really on a CD, DVD, or LD is a bunch of 0's and 1's (+ or -, if you prefer, but technically 0/1). Change the sequenceof all theses 0/1, and you have a different higher or lower frequency. I hope that makes little bit of sense. Also, aren't SACD's and their players supposed to respond to something like 100kHz?

    Wes
    Link: http://polkarmy.com/forums

    Panasonic TH-42PHD8UK 42" HDTV | Polk Audio SDA-SRS's (w/RDO's & Vampire Posts) + SVS PC+ 25-31 | AudioQuest Granite (mids) + BWA Silver (highs) | Cary Audio CAD-200 | Signal Cable Silver Resolution XLR's | Wyred 4 Sound STP/SE Pre | Signal Cable Silver Resolution XLR's | Cambridge Audio azur 840C--Wadia 170i + iPod jammed w/ lossless audio--Oppo 970 | Pure|AV PF31d

  3. #3

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    Default this is just a thought.........

    So don't shoot me if this is way off, or sounds uneducated because that is true....

    I'm thinking that it isn't a source limitation but that of the converter, would it not?? It would make sense to me that if the range of the amp is 20Khz, wouldn't it make sense that the converter have the same range?

    Assuming that it's true that most people only hear up to that range, that would make sense as well.

    Hmmm, I'll have to hit the books a little on that, now I am curious.

    Troy

  4. #4

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    Default freq. responses

    Start at the end of the reproduction chain, the speakers. There seem to be plenty of speakers rated over 20kHz., but nothing near 100kHz. The another problem is the amp. The vast majority roll off before they get very high, but there are a few that get up there. The last problem, of course, is the source. I'm pretty sure CD's are limited to exactly 20kHz. SACD, on the other hand, is rated up to 100kHz., I believe. However, the specs on Sony's top line $5000 player rated the actual response up to 50kHz, so that gives you an idea of real-world performance, I guess.

    As far as the harmonics go, I've heard similar arguments. I asked one salesman all the questions you just asked, and I think he fed me a line of BS. Anyway, he did say that B&K apparently did an experiement where they placed a brickwall filter at the amp's output at 50kHz. Then they played the speakers in a room full of "audiophiles." After awhile they switched the filter on and everyone turned to look at the stereo as if something had gone terribly wrong. That would add evidence to the whole harmonic thing. Who knows.

    Aaron

  5. #5

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    Default

    I have rather limited knowledge in this area, so don't shoot me if I don't know what I'm talking about, either. I believe that the upper frequency response limit on digital material is dependent upon the sampling frequency. I believe that the limit is one-half of the sampling frequency, so for a 44.1KHz CD, roughly 22Khz. Since the abrupt cutoff would be harsh-sounding, I think they employ some sort of filter to produce a more "natural-sounding" roll-off at 20Khz or so. SACD and DVD-A have higher sampling freq. and so are capable of higher freq. response.

    Again, I may be wrong on this.

    --Jason
    Last edited by jcaut; 09-28-2001 at 03:52 PM.

  6. #6

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    Default Sampling

    When one tries to sample a continuous time signal, the minimum sampling frequency needed is twice the higher frequency component of the signal in question. That's the key, the signal has to be band limited if we hope to get a perfect reconstruction. If it's not then aliasing occurs(high frequencies appear as low frequencies distorting the lower frequencies, much as one can see a tire rotating slower or in the opposite direction), that is why before sampling one has to use a low-pass filter to get rid of high (hopefully unnecesary, like noise) frequencies.

    Now, for the CD if i'm not mistaken, they use a really flat low pass filter up to 40 Khz, because a sharp one distorts the phase. Then they sample that 40Khz band limited signal, and once it is discrete time ( and also discrete amplitude because of quantization) they downsample by 2, basically taking every other sample, to get a signal with only frequencies up to 20 Khz more or less.

    One could sample as fast as one pleases, but then we have a storage problem....

    Hope somebody can make some sense of this:)

    Bernardo

  7. #7

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    Default Makes Sense to Me

    It makes my cd player sound good. Which in turn is amplified cleanly and accurately as possible by my amps. Then it is reproduced faithfully by "The Truth". What could make more sense? My turntable and cartridge TRY to faithfully reproduce all the music I like THAT I DON'T HAVE ON CD. I don't hear "warmth" from that combo, I hear surface noise, no matter how pristine the vinyl.

    George Grand (of the Jersey Grand's)

  8. #8

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    Default Well stated Bernardo...

    Which brings me to another idea:

    If most studio CD's only about half to 65% of the discs capacity, why not make a "smart" variable rate sampler CD player and use the entire capacity of the discs to get more quality and stuff. Actually, this probably work better with DVD-A since you can layer those things. Have one layer be a standard CD and another layer be the super-duper sampler rate version. Damn I have good ideas...

    Wes
    Link: http://polkarmy.com/forums

    Panasonic TH-42PHD8UK 42" HDTV | Polk Audio SDA-SRS's (w/RDO's & Vampire Posts) + SVS PC+ 25-31 | AudioQuest Granite (mids) + BWA Silver (highs) | Cary Audio CAD-200 | Signal Cable Silver Resolution XLR's | Wyred 4 Sound STP/SE Pre | Signal Cable Silver Resolution XLR's | Cambridge Audio azur 840C--Wadia 170i + iPod jammed w/ lossless audio--Oppo 970 | Pure|AV PF31d

  9. #9

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    Default Alllllllllrighty then....

    Fisher-Price record players tend to make a lot of noise...perhaps thats the issue?

    Yeah, I hear it to (surface noise), but there is something there extra, better. Maybe the warmth is inside me, bringing up good memories of my childhood and Dad spinning records on Saturday night, that atmosphere that said 'everything is ok in the world'....

    Nice responses guys, good thoughts and ideas....variable rate sampler...WAY cool.

    Cheers,
    Russ
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.

  10. #10

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    Default

    Seeing how you emphasized that Mexican food post the other day, there is no question about a great deal of "warmth" emanating from within you. HA!

    George Grand (of the Jersey Grand's)

  11. #11

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    Default

    I can smell that one from here!

    Wes
    Link: http://polkarmy.com/forums

    Panasonic TH-42PHD8UK 42" HDTV | Polk Audio SDA-SRS's (w/RDO's & Vampire Posts) + SVS PC+ 25-31 | AudioQuest Granite (mids) + BWA Silver (highs) | Cary Audio CAD-200 | Signal Cable Silver Resolution XLR's | Wyred 4 Sound STP/SE Pre | Signal Cable Silver Resolution XLR's | Cambridge Audio azur 840C--Wadia 170i + iPod jammed w/ lossless audio--Oppo 970 | Pure|AV PF31d

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