CD sound quality: now it's the Loudness Wars

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NullDevice
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Re: CD sound quality: now it's the Loudness Wars

Postby NullDevice » Sat Nov 16, 2013 12:47 pm

Huckleby wrote:Nobody has ever explained to me why CD parameters (44 KHZ, 16 bit) are inadequate to represent sounds for human hearing. People can't hear jackshit above 15Khz. I suppose there could be a tiny difference in processing music at 24 bits, but not storing the final product.


Bitrate does make a difference for noise floor and reproducable dynamic range. All sampling rate increases do is shove the frequency of aliasing/interpolation noise to a higher frequency. Given the human ear is limited at best at 20khz, it's pretty ludicrous.

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Re: CD sound quality: now it's the Loudness Wars

Postby Huckleby » Sat Nov 16, 2013 2:56 pm

NullDevice wrote: Bitrate does make a difference for noise floor and reproducable dynamic range.


I'm sure you meant bit size rather than rate. I did some googling to get my facts straight. Music stored on the very best analog tape had a dynamic range of about 60 DB. Did anybody ever complain about the sound quality of music on quality reel-to-reel tape?

You get 6 db of dynamic range for each bit. So storing music in 16 bits gives you 96 DB of dynamic range. The maximum dynamic range ever found in music is 90 DB - and that's really pushing it.

I used to be a software programmer in a audiology research lab. The standard for representing sound was 12-bits. 72 dB was plenty for all the experiments. Then as digital hardware got better and cheaper, 16 dB became the standard, with 96 dB being overkill.

The reason why 20-bit or 24-bit digital systems might offer something is in the sound processing. You get less error accumulated, I guess.

When you finally present the sound, it's inconceivable than more bits gets you anywhere. 20-bits takes you up to the threshold of pain (120 DB) for people with the most excellent hearing.



NullDevice wrote:All sampling rate increases do is shove the frequency of aliasing/interpolation noise to a higher frequency. Given the human ear is limited at best at 20khz, it's pretty ludicrous.


Right. And an older fart like me barely hears anything above 10Khz, frankly.

Higher sample rates than CD standard are useful for cat hearing. But human hearing - no way. (I guess somebody might consider the sharpness/quality of the analog anti-alias filters at the output, but 44Khz allows plenty of fudge.)

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Re: CD sound quality: now it's the Loudness Wars

Postby NullDevice » Sat Nov 16, 2013 6:36 pm

I'm sure you meant bit size rather than rate.


Right. Bit size. I was kind of getting ahead of myself. :)

I can see an argument for these ridiculous sample rates in a studio, *maybe*. Given most DSP and DAC oversamples like whoa and it doesn't really matter for analog gear, it's generally just an excuse to waste disk space.

Nobody complains about tape. Or vinyl. In fact there're a ton of processors built to simulate the saturation of tape and vinyl, so I don't know why everyone's like "OMG digital sucks!" Audiophiles like to get all snooty about vinyl, since it's analog - but for all the wrong reasons - there's real physical limits to what needles can reproduce, and proper mastering for vinyl requires a lot of gyrations to make it sound good, so it's not by any means a "pure" signal.

FWIW, I work with a young hipster kid and apparently cassettes are making a comeback with the hipster crowd.


I've noted this. It's another ridiculous affectation you can probably blame some dude in Billyburg for. It'll pass.

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Re: CD sound quality: now it's the Loudness Wars

Postby snoqueen » Sat Nov 16, 2013 6:52 pm

It'll pass as soon as they spend a couple afternoons trying to rewind a cassette after the tape unspooled itself and looped all over the inside of the tape player.

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Re: CD sound quality: now it's the Loudness Wars

Postby david cohen » Sun Nov 17, 2013 12:01 pm

If you've ever listened to high resolution audio that hasn't been sample rate converted and dithered (like Mobile Fidelity Sound Lab 24 bit/192khz stuff), you can perceive the difference from the CD (16/44.1) or the LP pressings.

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Re: CD sound quality: now it's the Loudness Wars

Postby Huckleby » Sun Nov 17, 2013 12:18 pm

david cohen wrote:If you've ever listened to high resolution audio that hasn't been sample rate converted and dithered (like Mobile Fidelity Sound Lab 24 bit/192khz stuff), you can perceive the difference from the CD (16/44.1) or the LP pressings.


I believe, but I just can't imagine why this is true. Is it actually the superior analog electronics in the system?

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Re: CD sound quality: now it's the Loudness Wars

Postby david cohen » Sun Nov 17, 2013 9:04 pm

Define "system"? On playback, with a top notch D>A converter and attendant preamp/power amp/speaker combo....or the original A>D process? I think you really have to have both but the difference to my ears is truer bass and this silky sound (not brittle like many CDs). Plus, if you listen natively (without error correction via the CD playback process) that makes a big difference.

That said, I spent most of last night listening to vinyl and analog distortion/saturation is really nice too:)

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Re: CD sound quality: now it's the Loudness Wars

Postby Huckleby » Sun Nov 17, 2013 10:52 pm

david cohen wrote: On playback, with a top notch D>A converter and attendant preamp/power amp/speaker combo....or the original A>D process?


There are analog circuits as part of the the D-to-A process. For instance anti-alias filters. Ideally, those filters would be perfectly sharp, and take-out only frequencies about the Nyquist frequency. Well, if you have a high sample rate, it makes imperfections in the curve of the output filter less relevant.

Honestly, I'll accept the "black magic" explanation. My very basic understanding of hearing and signal processing (no false modesty, I am at the dangerous level of knowledge) don't explain how those high end systems achieve better results.

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Re: CD sound quality: now it's the Loudness Wars

Postby NullDevice » Thu Nov 21, 2013 8:50 pm

I'm honestly not sold. I've got good DAC/ADC (Metric Halo makes some of the best in the biz), I've got a treated room, I've got some rather nice studio monitors (they claim to reproduce ultrasonics), and rather good ears for this sort of thing. I've mixed at 44, 48, and 96 and...there's a slight difference but I can't really say either is "better" in a blind listening test.

Sometimes the primary difference in sound has nothing to do with the signal, it's just the processing used to get it to that medium (like vinyl).

And there's this, too: http://xiph.org/~xiphmont/demo/neil-young.html

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Re: CD sound quality: now it's the Loudness Wars

Postby Huckleby » Thu Nov 21, 2013 10:49 pm



An awful amount of good information in that article.

The guy explains why 192 KHz could actually be worse than 44KHz:

"192kHz digital music files offer no benefits. They're not quite neutral either; practical fidelity is slightly worse. The ultrasonics are a liability during playback.

Neither audio transducers nor power amplifiers are free of distortion, and distortion tends to increase rapidly at the lowest and highest frequencies. If the same transducer reproduces ultrasonics along with audible content, any nonlinearity will shift some of the ultrasonic content down into the audible range as an uncontrolled spray of intermodulation distortion products covering the entire audible spectrum. Nonlinearity in a power amplifier will produce the same effect. The effect is very slight, but listening tests have confirmed that both effects can be audible."

Ironically, this nonlinearity business might also explain why very high sample rates could matter. The cochlea is also a transducer with non-linearities. Could it be that a mix of very high frequencies interact in the cochlea to produce audible vibrations? Maybe you need to sample music at a high rate to preserve that information. I don't know if it is a likely explanation, but at least it is non-mystical.

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Re: CD sound quality: now it's the Loudness Wars

Postby raw-tracks » Fri Nov 22, 2013 12:26 pm

Here's a great article about bit depth:

http://www.sonicscoop.com/2013/08/29/wh ... bly-wrong/


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