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Discussion in 'Sound Science' started by jonasras, Mar 5, 2013.
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    I get a headache everytime I read one of your posts.

    Not only are you missing the point of my statement entirely, you're clearly just arguing for argument's sake. Enjoy.
  2. sonitus mirus
    Good stuff, as usual.  With regards to "SD" vs "HD", I was mostly referring to the current market trends where consumer options for mainstream music are either MP3 or AAC from mega stores such as Amazon, Apple, or Google vs. the heavily marked up HD files.  If I could get a FLAC/ALAC version at CD quality for all of my music and at a similar price that I can currently buy a new CD, I'd be happy.  Mostly the lossy versions are audibly transparent, but not in every situation for every listener on every system.  For personal confidence, if I am going to purchase music, I'd want it to be available in a format with no potential compromises in sound quality.  Currently I purchase CDs, used or new, when I need to fill in gaps that a streaming music service does not support.  It would be great if lossless version were made available to purchase for entire catalogs.  It was only the foolishness of the major record labels that had for so long been able to control distribution that they failed to see any benefit in changing their methods.  The only way they allow online sales of lossless quality files is to make them available at outrageous prices in ludicrous formats that nobody has shown to be sonically superior to Red Book in any meaningful way.  I'm fine with 24/96 or any format that is established as the norm for online distribution, but I'm not going to pay $30 for an online digital version if the CD is available to buy at Amazon for $7.  
  3. gregorio
    Me too. What annoys me is that this format should be 16/44.1 or a FLAC/ALAC equivalent. In practise though it's usually SACD/DSD or 192/96/24, purely for marketing purposes. Consumers presumably won't cough up for a huge mark-up between two different versions both at 16/44.1 but apparently will if one of the versions is only available in a different (higher data) format. While some mark up is justified for a higher quality version (be it 16/44.1 or higher), the consumer is to some degree effectively being scammed, very effectively actually because so many never even realise they are being scammed!
    I sometimes wonder where we would be if the industry had focused on audio quality rather than on audio formats. Maybe one day it will come back round but for now the push is towards ever more ludicrous formats, formats which if anything degrade audio quality rather than enhance it.
  4. Hi-Fi'er
    Truth about Audio: https://www.youtube.com/watch?v=Z5S_DI99wd8&feature=youtu.be
    sonitus mirus likes this.
  5. wnmnkh Contributor
    Yes. No doubt Dr. Waldrep is one of the sane voices regarding 24bit stuffs. You may also want to visit his blog site too: www.realhd-audio.com
    That was an overall disappointing video, though there were some good takeaways from it.
    He spent the entire time arguing that making 24/192 versions of recordings that were recorded at far lower fidelity is pointless. Who the heck on this planet would argue that (besides Neil Young, apparently... who is biased since he needs to make sales)? As he eloquently put... You can't use a CD as a source to generate content that sounds better than a CD.
    There is a far more involved, and quite frankly better and more important, discussion to be had on the value of recordings that captured at 24/192 in the first place vs. 44.1/16 for example. The speaker certainly seems to think there is value in that, though he himself readily admits he doesn't know why and "hopes" that the brain can use some of that extra content. He in fact does his own recordings with higher resolution (I watched the video last night and forgot the exact number, 96/24 maybe?)... 
    As for myself, I think I have the same opinion as the speaker.... I want the exact acoustics in the studio or live performance to captured and reproduced, regardless of whether or not the content is audible... If a guitar produces some high frequency content beyond 20KHz for example, I want that in the recording and played back by my hardware despite the fact that I can't hear that content. 
  7. sonitus mirus
    I tend to agree with your agreement.  However, with higher recorded frequencies, I believe that it is possible to introduce distortion (IMD?) that might negatively impact what is being heard.  So, what may not have been an issue listening to something live might not work correctly through speakers that have to struggle to play back the wider frequency range when all instruments/voices are combined into a single audio signal.   A solution might be to simply use speakers that cannot reproduce ultrasound.  Some speaker setups using 24/192 files could potentially be making things worse for the listener.
    This is the greater discussion that I wish the speaker had gone into. It's an interesting topic for sure. 
  9. spruce music

    On another forum last year there was circulating a 96 khz file with 30 khz and 33 khz recorded at a high level. So you could test for the 3 khz imd result. Mostly with headphones but also with speakers no one could hear it until they pushed the amps too far. Seems transducers were less of a problem than what is usually assumed.
    With 30KHz and 33KHz, IMD spurs would show up at 27KHZ and 36KHz. I wouldn't be able hear that far up in the spectrum, let alone for spurs that are 60+dB down. 
    I suspect what likely happened is that people pushed the amps so far up it caused some periodic distortions at the maxima and minima of the tones, causing audible harmonics which is what they heard. 
    Of course what I'm saying is all speculation, I have no way of going back in time and measuring it. 
  11. spruce music

    The idea was to look for the difference tone at 3 khz. That is where imd will usually be audible.
    Good point. I'm used to talking about intermod in terms of 3rd order products. Those are typically closest to our signal of interest and usually loudest. 
    The 2nd order difference tone will be the quietest usually. 
  13. pinnahertz
    The discuss of IMD as a by-product of bandwidth and system nonlinearity really only scratches the surface.  The correlation between system bandwidth and IMD is spongy at best, as there are other factors to consider.
    A good reference paper that starts to get at the meat of the issue is "Spectral Contamination Measurement" by Deane Jensen and Gary Sokolich, AES 85th Convention, November 1988 (available at AES.org).  The went beyond two-tone IMD and created a several excitation "patterns", like energy at 120Hz intervals from 10kHz to 25kHz with a measurement window from 30Hz to 8kHz.  Their work started to get to the roof of why amplifiers with lower gain-bandwidth product sound worse than ones with higher gain-bandwidth product, etc.  They tested digital systems, analog tape recorders, all-pass filters, amps, and more.  I'd read this one before theorizing too much about ultrasonics and IMD.
    sonitus mirus likes this.
  14. spruce music

    I read that paper around 5 years ago.  Tried this test and didn't find it revealing anything new.  Maybe modern gear has such high gain bandwidth op-amps it isn't a problem.  I found spectral contamination to show me nothing more useful than two tone IMD.  I also have used a pair or three or 4 swept tones.  Equal spacing.  Like 500 hz or 1khz difference.  Run the sweep starting with 1khz and 2 khz with both sweeping to 20 khz.  Again I don't recall any of the few pieces of gear tested to show much different than just using 19 and 20 khz. 
  15. pinnahertz
    What did you use to generate the 125-tone test signal?  Did you apply 10kHz HPF before the DUT and the 8kHz LPF after the DUT? What devices did you test?
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