There is a lot of information and a lot of misinformation about audio out there on the World Wide Web. Who and what to believe is sometimes challenging for a layman. Heck, it’s hard for an experienced engineer to make sense out of it. I fully admit that there are people writing papers about the value of DSD and the fallacies of 192 kHz/24-bits that might know more than I do. But I’m pretty good at researching and discovering the truth…or at least a truth uncolored by hype and self-interest. So when I got an email from Rob the other day pointing me to an article by Monty at xiph.org entitled, “24/192 Music Downloads…and why they make no sense”, I knew I had to respond.
First, let me state that I like Monty’s overall approach. He’s unapologetic, rationale and has plenty of technical knowledge to speak with some authority on the topic. He gets a lot of things right but overlooks other things. I’d like to discuss some of the points that he makes in the rather lengthy article over several posts. Today, the main topic is his claim that 24-bits makes no sense. They do and here’s why.
He states, “OK, so 192kHz music files make no sense. Covered, done.
What about 16 bit vs. 24-bit audio? It’s true that 16 bit linear PCM audio does not quite cover the entire theoretical dynamic range of the human ear in ideal conditions. Also, there are (and always will be) reasons to use more than 16 bits in recording and production.
None of that is relevant to playback; here 24-bit audio is as useless as 192kHz sampling. The good news is that at least 24-bit depth doesn’t harm fidelity. It just doesn’t help, and also wastes space.”
The focus of his discussion regarding 24-bits for downloaded files is based on the recognition of the status quo and the limits that have been accepted by (or forced on) recording engineers and producers. The music business has long used radio as a primary means of promoting new songs and artists. If the record companies want their music to he heard over the background noise of your automobile, then they instruct the mastering guys and gals to push the volume and reduce or even eliminate dynamic range. It’s called the “loudness wars” and it has essentially dictated the number of bits that are actually required to completely capture and deliver a highly compressed commercial record.
And pop/rock music isn’t the only genre afflicted by this contagion. Classical music and jazz are subjected to the same processing although usually to a lesser degree.
The article states that most records don’t have sufficient dynamic range to utilize the potential range of even 16-bits. I would generally agree…but some of us have been successful in recording and releasing projects using 24-bits that actually do eclipse 16-bits or the theoretical limits of 96 dB SNR. It’s certainly not every piece of music that has more than 96 dB of dynamic range.
Figure 1 – A Chart Showing the Dynamic/Electrical Range of Sound, Music and Audio Systems
However, the instantly recognizable Ravel Bolero that I recorded in Bucharest in the summer of 2001 does. The background level of the Atheneum in downtown Bucharest is a very quiet place late at night. The opening snare drum rhythmic motif of the piece is played very quietly. I can distinctly recall how many times we had the percussionist play the opening to get the least volume with good articulation and detail.
And we all know how big the piece gets at the final modulation section. The whole 120 piece orchestra is playing at maximum volume and pings an SPL meter beyond 125 db for brief moments. This simply cannot be captured within 16-bits without some sort of dynamic compression (as is usually the case for vinyl and CDs) but we can deliver all of that range with 24-bits!
A rather funny side note: the review that I got of that recording in The Absolute Sound magazine stated that the recording had “too much dynamic range” in the reviewer’s opinion! So what am I supposed to do? The conductor and the players do their thing and I captured it without modifying the dynamics…that’s what I’m supposed to do. What I didn’t do was screw with the dynamics during the postproduction phase of the project. The reviewer needs to get a better and quieter listening environment.
So finally we have technology that can capture AND deliver the full potential dynamic range of human hearing. Analog tape can’t do it. Vinyl LPs can’t do it and 16-bit CDs can’t do it either. The dynamic potential of a 24-bit recording system can AND a 24-bit file can be delivered to consumers on a Blu-ray Disc or a DVD-Audio disc or as a download can too. If you have a current state-of-the-art DAC like the new DAC2 from Benchmark (which has a dynamic range of over 130 dB!) then you can reproduce the entire dynamic range of any piece of music. BUT THE RECORDING HAS TO HAVE BEEN MADE WITH THAT MUCH RANGE!
Admittedly, virtually all commercial music doesn’t even come close to exceeding 16-bits worth of dynamic range. So does that mean I compromise my efforts to live within the constraints of 16-bits. No it doesn’t. And whether your room and system can handle that much dynamic range is another possible constraint. But I don’t have to worry about that…you do.
Monty describes the current state of affairs but ignores those of us that are striving and delivering more. He didn’t factor that into his article.