Comment by Derbasti
14 years ago
He raises a lot of valid points. However...
192 kHz is clearly overkill for listening. Not so for further editing of the data.
Same goes for 16/24 bit, however, the difference between 16 and 24 bit is actually audible.
44100 is not a bad sampling rate, but it necessitates very sharp aliasing filters, which are audibly bad. A bit more headroom is well needed there.
That bit about intermodulation distortion is complete bogus. He talks about problems when resampling high-fs audio data. However, you would never do that. You would digitally process 192kHz all the way. Only your loudspeakers or ears would introduce a high-pass filter, and a rather bening (flat) one at that. There is certainly no aliasing going on there unless you resample (wrongly). Intermodulation distortion is not the fault of the sample rate.
I mayored in hearing technology. Calling 192/24 worse than 44.1/16 is total BS. How useful it is is a different debate.
>Same goes for 16/24 bit, however, the difference between 16 and 24 bit is actually audible.
This [1] (widely accepted in the scientific audio community) study's conclusions disagree with your assertion.
>44100 is not a bad sampling rate, but it necessitates very sharp aliasing filters, which are audibly bad.
This is not the 1980s, hardware has progressed beyond that point. Modern (i.e. anything from 1995 onwards) DACs do not suffer from aliasing problems. Also see [1]
>That bit about intermodulation distortion is complete bogus. He talks about problems when resampling high-fs audio data.
I did not notice that in the article. It talks about IMD in the context of the analog chain and the transducers following the DAC, and it's possible that high frequencies can increase it.
[1] http://www.aes.org/e-lib/browse.cfm?elib=14195
> Modern (i.e. anything from 1995 onwards) DACs do not suffer from aliasing problems.
True, but they do so using (long, high-quality) high-cut filters. And these filters are pretty sharp, as they have to close within, say, 18-22.1 kHz. You can design them as linear-phase FIR filters with oversampling and all the good stuff, but physics dictates that sharp filters introduce distortion. A sharp filter like that is audible.
I'm not aware of any (blind) listening tests actually showing that a modern, high-quality DAC for 44 kHz audio introduces audible distortion compared to a similarly high-quality DAC for, say, 96 kHz audio, though. It's not theoretically impossible that the lowpass would introduce some sort of noticeable distortion, but I haven't run into substantiated evidence that it actually does.
44100 is not a bad sampling rate, but it necessitates very sharp aliasing filters,
When you're talking about recording, sure, but in terms of storage and playback, we solved that problem 20 years ago with oversampling.
You will still need a aliasing filter that cuts off between, say, 18 and 22.5 kHz to avoid aliasing noise. That is one sharp filter no matter how you look at it. You can use a high quality, long, linear-phase FIR filter, but you can't cheat physics: sharp filters necesserily introduce distortion, and such a sharp filter so close to the hearing threshold does not go unnoticed.
I don't see how a sharp filter could be needed if the DAC is oversampling.
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Same goes for 16/24 bit, however, the difference between 16 and 24 bit is actually audible
No, the difference is not audible at all. At 16 bits of depth on a normal low-level audio signal (~0.3 volts), we're talking about less than 0.000005 volts per amplitude step. This difference gets lost in the THD already at the DAC in your audio output stage. Then it gets lost again in the amplifier. And again in the cable to your speakers or headphones. And then it gets lost again in the speaker elements. What survives in a normal low-level audio signal is about 14 bits of resolution.
44100 is not a bad sampling rate, but it necessitates very sharp aliasing filters, which are audibly bad. A bit more headroom is well needed there.
44.1khz IS a bad sampling rate for accurately reproducing anything except a triangle wave or square wave above 5khz.
why do you think "This difference gets lost in the THD already at the DAC "? Do you have numbers to back it up? What's the noise floor of DAC? What's the noise floor of an output stage? Do you have the number?
The number is somewhere between the amplitude of an ant pissing on cotton, and an ant not even thinking about pissing on cotton.
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Many years of building audio equipment (in particular analog synthesizers), and equally many years of being meticulously anal with getting the best components for my circuits, reading specifications of down to every single op-amp I've ever employed, is why I think so.
I am not saying that there aren't any DACs on the planet that can't handle five millionths of a volt, but I am saying that five millionths of a volt isn't surviving through the particular DACs and the rest of the electronics used in your PC/living room hi-fi audio equipment.
why do you think "This difference gets lost in the THD already at the DAC "? Do you have numbers to back it up? What's the noise floor of DAC? What's the noise floor of an output stage? Do you have the number?
Heh, it's funny to see this late-nineties debate get re-hashed here. Also kind of fun.
If it were true that there's no audible difference between 16 and 24 bit, companies like Alesis, Otari, ProTools, etc. wouldn't have spent the last 15 years ditching 16 bit like an old pair of smelly sneakers. (better metaphors welcome).
Seriously, anyone who has sat down in a real listening environment for 5 minutes A/Bing 16 vs 20 bit, 16 vs 24, etc. hears the difference immediately. There's no question. This is why you can buy ADAT 16 bit 'blackfaces' for $100, down from their original $4,000.
Sure, moving up from 16bit recording was an improvement, but having done engineering for a company listed above for over a decade, I can tell you that we went 24bit/192kHz because of market demand, not for any real technical reasons. We thought it was fairly unnecessary ourselves. It was also kind of an arms race with other companies, much like the megapixel arms race for digital cameras.
Bigger numbers are better. Right?
It's all marketing, baby!
...And the new Pro Tools 10 just added the ability to record in 32-bit floating point. http://www.avid.com/US/products/Pro-Tools-Software
Yes, and anyone who has ever sat down infront of an LCD flatscreen watching their favorite movie on DVD/BD using gold-plated $200 HDMI cable instead of $4.99 Walmart HDMI cable see the extra sharpness immediately. This is why non-gold plated non-OFC HDMI cables are down to $4.99 a piece from their original $49.99 during introduction.
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