speakers for 24/96 audio

07-05-11: Almarg
...we are not hearing the nanoseconds or picoseconds of timing error itself. What we are hearing are the spectral components corresponding to the FLUCTUATION in timing among different clock periods...

That's what I suspected, Al, but I wasn't sure.

And thanks for your explanation of jitter. I was aware that jitter resulted in frequency modulation, but I didn't know that it was a kind of intermodulation distortion. Your explanation is much appreciated.

Shadorne - You may be right that Kunchur's methodology is flawed. I've read a few other experiments on human temporal resolution with similar methodologies, but my memory of them is a little vague. In any case, I have a question about your observation that "Some sample rates are noted for being better than others for reducing audible jitter." I'd be interested to hear a technical explanation for why that is the case.

Finally, I have a general question about high resolution audio that anyone might be able to answer:

My understanding is that the principal advantage of larger bit depth is greater dynamic range. What is the principal advantage of higher sampling rates, if it is not better temporal resolution?

Bryon

What is the principal advantage of higher sampling rates, if it is not better temporal resolution?

None above redbook CD except it allows cheaper and better filtering which may improve very slightly the audible band. However, higher sample rates do allow you to go to one bit resolution (like SACD format which is a DSD stream but SACD has very high levels of out of band noise - so to be honest I am not sure I accept that it is even as good as 24 bit/96)

What is the principal advantage of higher sampling rates, if it is not better temporal resolution?

Yes, as Shadorne indicated the principal advantage is that it dramatically relaxes the rolloff requirements for anti-aliasing filters (in the recording process) and reconstruction filters (in the playback process). Or it makes it possible to avoid the use of techniques that have been used to relax those requirements, which have their own tradeoffs (e.g., oversampling + noise shaping).

It should be kept in mind that not only will 44.1kHz sampling be unable to capture signal frequencies at or above 22.05kHz, but the a/d converter used in the recording process must not be exposed to those frequency components. Otherwise "aliasing" will occur, resulting in those ultrasonic frequencies appearing in the digital data as audible frequencies.

Therefore an a/d converter that doesn't use oversampling or other special techniques must be preceded by a low pass filter that is flat to 20kHz, but has rolled off to the point of inaudibility in about 1/10th of an octave, at 22.05kHz. That is an EXTREMELY sharp rolloff, and, besides being expensive to manufacture, that kind of filter can have the sonic effects Kijanki described above in his post of 6/27, and the effect described in my second post of 6/30.

In contrast, 96kHz sampling would make it possible to allow more than a full octave for the same rolloff to occur (at 48kHz rather than 22.05kHz).

Similar considerations apply to the playback process, with respect to the "reconstruction filter," which refers to a low pass filter used to eliminate the stepped character of the d/a converter device's output.

Best regards,
-- Al

Sounds like the consensus is that the original CD redbook format engineers did a more than adequate job, at least in theory.

So does that mean that when we hear deficiencies in specific redbook CDs compared to other formats (say R2R or very good vinyl even) that it is because of poor execution somewhere in the implementation , either in the recording or playback process or equipment, or most likely even both?

I like to think so but I have not heard the near perfectly created CD on the near perfectly executed system in a viable test scenario compared to other high quality formats yet that would confirm this, so I am not so sure reality reflects the theory in practice quite yet?

Has anybody else heard something specifically that has them convinced?

On my system, I think the issue is a wash, but I have done some imperfect a/b comparisons on very high end dealer reference systems where it was not, especially in comparison to R2R and with better large scale orchestral recordings involving massed strings in particular.

"Sounds like the consensus is that the original CD redbook format engineers did a more than adequate job, at least in theory."

Well, I would have said the red book CD is "just adequate". I think reducing the word length or the sampling rate might have audible effects, so "just adequate" comes to mind.

As for comparisons to "other media", are you talking about analog? For me at least, vinyl doesn't come close, no matter what you spend. Analog tape can sound very, very good, but except for our own master tapes, where would one get source material? In the past I've heard 1/2" 15 or 30ips tape with Dolby sound spectacular in a studio, but how many of us have access to such a thing?

Here's a better question: is there any significant amount of content coming out of the recording industry these days that requires a medium superior to a 16/44 CD? Perhaps some rare examples in the classical venue, but it seems like none in jazz, rock, pop, country, new age, or whatever. Or am I wrong?