Today's post is the second in a three part series on the topic of mastering from producer Gary Gray.

Take it away Gary...

DITHERING: Deception or Dire Necessity?

One of the Mysteries of Mastering is Dithering.  Start a conversation in a room full of audio engineers on the subject of Dithering. Oh boy. Watch out. You get two reactions; people who start gushing out complicated algorithmic mathematical equations late into the night, or closed mouth absolute total silence.

Ironically, it is on the subject of Dithering in Mr. Katz’ book “Mastering Audio – The Art and The Science,” that many students have walked away, frustrated, scratching their heads, wondering what it was they just read, and wondering how in the hell they were going to apply dithering to their own recordings. If you were one of those people, don’t feel alone.

I am not here to sell anything or to particularly endorse or denounce anyone or any product. I am here to share the honest results of my observations, experiments and research so that you can evaluate them for yourself and so that you can succeed better in your career, and in this case, do so by learning as much as you can about Mastering.

Though a few paragraphs earlier I named Bob Katz one of the heroes in our industry (which he is) -- like all heroes, he is not perfect. Out of the 325 pages of his excellent book, there is one chapter, Chapter 4 “Wordlengths and Dither,” from page 53 to page 64 that, in my opinion, based on my own observations, you can skip.

Skip?  Yes. In fact, if you notice, I am not even offering you a definition of Dithering. Why? Because it will just trip you up and waste your time. If dithering were a key element or even had any part whatsoever in my own successes in Licensing Music, or in anyone’s success in Licensing Music – believe me, I’d be all over it like white on rice. You would be getting every possible detailed definition and “how-to’s” that I could get my hands on.  

This is based not only on extensive research, but is based, with total confidence, on controlled experiments and tests that I conducted myself in order to answer this question: Is the action of Dithering necessary at all? Can you HEAR the difference between a dithered recording and an un-dithered recording? If I am trying to get my recordings shopped for licensing deals, do I need to know anything about dithering?

The answer to the last question above is No. The test? I used a technology that, ironically, I learned from Mr. Katz, called “the null test.”  If you take a recording, duplicate it, line up both recordings perfectly on two separate tracks, and then reverse the phase of one of those two recordings, keeping the volumes identical -- when you hit play, you will hear: silence.  If there are ANY differences between those recordings, you will hear something. If they are the same, you will hear nothing during a null test. That’s why it’s called a “null” test.

I took a mix and mastered it without dithering.  I then exported the exact same mix again, without changing any mastering settings – except for one; I added dithering.  I then took those two recordings, ensured they were lined up perfectly, put one out of phase, made sure the volumes were exactly the same, and I CRANKED UP my studio system louder than it’s ever been turned up before.  I hit play – if there were ANY audible difference between those two recordings, I would have heard SOMETHING.  The result? Silence. Pure silence all the way through the entire track – from beginning to end. 

Interestingly, this was also confirmed independently through research by Steve Massey, an electrical engineer who owns and operates Massey Plugins, where he has designed and built several very popular audio plug-ins. Steve formerly worked for ProTools and Digidesign, designing and helping to build Pro-Tools plug-ins. Here is what Steve says about dithering:

“If dither makes such a perceptible improvement to fidelity, then shouldn't it be completely obvious when that plug-in gets latched into the correct slot and the audio is flowing through the correct path? Shouldn't the standard, somewhat flippant, internet forum answer of "Just use your ears!" be applicable here? It's not -- no one ever says this with regards to dithering. That's because, it's hard to stand behind such a statement with any confidence about a technology that does not exist.” 

You can find out more about the results of my tests and more information about Mr. Massey in the course. (Note: I also learned that mp3’s are like snowflakes, which I did not know before. No two [even of the same source material] are created equal. When running the test on wav files, I heard absolutely nothing; silence.  When running the test on mp3’s I heard something! Hours and hours of further testing revealed that it wasn’t the dithering that was making the difference on mp3’s – I got the exact same sound from two identical mp3 recordings, both with dithering and both without dithering. I found out that the compression algorithm of mp3 converters work in a random fashion.)

Dithering, then, is a perfect example of The Emperor’s New Clothes. And, unfortunately, the “procession” continues.  Case in point: there is a website which “proves” that dithering is audible. And on that website – it is!  However, if you miss the fine print, you will fail to notice that the recordings that were dithered were 8 bit recordings. No engineers today ever deal with anything close to 8 bit recording technology. 8 bit recordings are distorted and garbage.  Was dithering once valid?  Yes, in the early days of digital technology it was valid, but it is no longer a valid or necessary activity for anyone who is trying to land licensing deals.  Whether it is necessary or valid for anyone today, I leave up to each individual engineer for experimentation and observation. Simply listen to dithered and undithered tracks, and decide for yourself. And yet, as I said, the “Emperor’s procession” continues: articles, forums, books, videos and authorities preaching the wisdom and importance of dithering.

Another test I conducted to see if dithering made any difference whatsoever was this:  I kept reading that dithering was helpful on recordings that contained high frequency ambient passages, especially exposed, long, high-frequency legato notes with sibilance, such as cymbals and cymbal crashes with long reverb trails. Supposedly, dithering helps keep artifacts and dropouts from occurring on such passages.

So I recorded some cymbal work with reverb – with a long reverb trail.  And then I mixed and mastered the track with cymbal work and long reverb trails. I mastered two versions – one with dithering and one without. I cranked up the playback to see if the undithered version had any problems with artifacts or dropouts.  I also listened to the dithered version. Any perceptible difference?  None. (Note: you should perform this test on your own DAW, because all DAW’s, contrary to popular belief, are NOT created equal. Per tests I read about Pro Tools and Digital Performer, these two were the two lowest quality DAWs in this category. Does that mean you need to change your DAW? No. Has anyone had a licensing deal kicked back because of Dithering problems from their Pro Tools or Digital Performer DAW? NO! Again, I’m just sharing with you the results of my research. I myself use one of the highest quality DAWs on the market; Cubase. But that doesn’t mean I’ll get any more or less Licensing Deals than you.)

And the ultimate test? Without dithering, two recent recordings I mastered were played on National Radio, without a word from any quality control personnel regarding any lowered quality of my recordings due to no dithering, and a recording that I mixed and mastered (without dither) was accepted by one of the top Music Supervisors in Hollywood as a single on the prestigious Concord Records Label for a Dennis Quaid movie soundtrack album. I’ve never heard a Music Supervisor or Quality Control person ever complain about dithering, or ever exclaim how good a recording was because of the great dithering job! I’ve never even heard them say the word!  And to me, no further tests are necessary.  

If you actually read Chapter 4 on dithering in Mr. Katz book, you could easily (I’m not kidding) spend 4 to 6 hours (or more!) on those 12 pages, just trying to work out the super-complicated algorithmic mathematics regarding wordlengths and dithering. Dithering DOES, in fact, do something to the track; it’s just that what it does is mathematical and is not audible. The remainder of his book is incredibly workable and amazing, but, in my opinion, Chapter 4 is not a Chapter I would even bother to read.

But companies which make dithering plug-ins would rather not discontinue products that they are making money from, and authorities who tend to defend rather than observe continue to exist, so the Emperor’s procession continues.

And by the way, how Steve Massey discovered that dithering doesn’t make any difference at all was by mistake -- after one of his plug-ins was released internationally, a plug in that was designed to do automatic dithering; it was found to have been released with a bug in it, he quickly fixed the bug and re-released the updated version. However, the earlier version had been out for several months and had been being used by thousands of users all around the world, including top producers and engineers – without a single complaint. None of the end-users, nor Steve himself, noticed that the automatic dithering was not working.  He only happened to find out by running complex algorithmic mathematical tests on the plug-in design. He fixed it because of his standards of service to his clients, not for audio purposes.

This then led Steve to discover more about the unnecessary science we call dithering.  He summed it up nicely:

“If dithering makes no difference, how has the concept lived on for so long? I think because it is mathematically validated, it has allowed the engineers at pro audio companies to say, with confidence, to their marketing departments that the inclusion of dithering has made their product better over the competition. That's great! I imagine marketing people love positive specifications and catch-words which they don't have to create themselves. Anything that is easily quantified and can be succinctly composed into the marketing text is great for the unimaginative salesperson. Examples of such marketing-driven myths are common in the technology market. 64-bit floating-point audio! Awesome! How in the world could that not be better than 32-bit floating-point audio? 64 is twice the size of 32. Six Megapixels is of course better 5 megapixels! (Like with most bullet-points and talking points, these metrics ignore the subtleties and/or disregard all the other equally important elements that were compromised in reaching that isolated specification.)

“But, I think the primary reason dither lives on is because the public itself has embraced it wholeheartedly, beyond simple influences of marketing. Why? I believe it's a bit like humanity’s attachment to the supernatural. People seem to possess, myself included, an overwhelming desire to imagine their perceptions of the world to be more subtle and more magical than they actually are. Even though no one has ever truly witnessed the effects of dither, we have faith in its power. And, since it's impossible to prove or refute something that you cannot hear (or see, or touch), the ghost of dither lives on...” – Steve Massey

Steve designs, builds and distributes excellent plug-ins at Masseyplugins.com. All of his plug-ins come in a free version, with an open-ended never ending trial period.  The paid versions have a few more options than the free, but all are excellent quality. I’m not trying to get you to buy his products – but I want you to know that I consider Steve a “hero” in our story and I believe that he is helping the community of International Independent Musicians and the Music Industry as a whole in a huge way. So, for that reason, I support his efforts.

I’m not saying that others won’t disagree with my findings. They may find valid reasons for dithering in some cases. What I’m doing is giving you workable information that will help you get your music licensed. Period.   

Part 3 Coming Monday...