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Omnia.9 Undo - A Cease Fire in Radio's Loudness Wars

Posted by Leif Claesson on Mar 11, 2014 10:26:00 AM

Omnia 9We've all heard about loudness wars on the airwaves, but you may not be aware of the loudness war in the music industry, or at least not how far it has progressed.

Nobody wants to release a song quieter than other contemporary releases. Few want to just match the loudness, most seem to want to release their music louder than other contemporary releases. The reasons are not clearly known. Perhaps there is a misconception that a loud release will cut through better on the radio. Perhaps it's human nature. Perhaps some people think their music will be a bigger hit if it's louder.

How does Undo work? And why do we need it?

Radio is partly to blame as we've had our own loudness wars ever since the first distortion-cancelled clipper was invented in the 1970s, but enough is enough; it has gotten out of hand.

Frank Foti and Robert Orban collaborated on an article about the subject a few years ago. Anyone in the industry knows that when those two actually agree on something, we'd better perk our ears up. Alas, nobody in the recording industry did.

Allow me to illustrate the progression of the loudness war in waveform (oscilloscope) pictures, with a few random but representative selections.

First, here is a kick drum from the original CD release of Dire Straits’ "Money for Nothing" from 1985:

Excerpt from Dire Straits' "Money for Nothing"

The lines are at 0dB full scale. Notice how they weren't worried about maximizing the volume at all -- the industry had just gained 30dB signal to noise ratio due to the transition from Vinyl to CD (reducing background noise by a factor of a few thousand to one). They had headroom which they could use -- or not! It sounded fantastic, and still does today, provided you turn your volume control up.

Next, Alanis Morissette’s "Ironic" from 1995. Here, the waveform is maximized without being modified. 1995 was (depending on your perspective) a relatively long time ago. In technology terms, it's eons ago. GSM phones were just coming out, computers counted their hard drives in megabytes (not terabytes), and people generally connected to the internet with 14.4 Kbps modems. As far back as that was, that's when we ran out of headroom on CDs.

Excerpt from Alanis Morissette's "Ironic"

This recording is sonically unaffected by the loudness war, but to go any further, we'll have to do something about those pesky peaks.

Then came 1999, with Red Hot Chili Peppers and their Californication album. This was the first time I personally took notice just from hearing it in the background at a party. "Did you blow your speakers or something?"

Excerpt from Red Hot Chili Peppers' "Scar Tissue"

Although it doesn't look all that clipped by today's standards, it sounded horrific because of how it was mastered: they simply turned it up. No limiting, no distortion-cancelled clipping, not even oversampling (to prevent aliasing) – they just turned up the level and let it overload. That, coupled with a sparse spectrum (clean bass line, clean electric guitar, clean voice) meant the clipping distortion cut through like nails on a chalk board, as there was nothing to mask it. The Chili Peppers were pioneers in this type of mastering, but around 2003, most of the music industry followed.

On Green Day's "Wake Me Up When September Ends", every single kick drum is a squarewave. This changes the sound of the kick drum from a kick to a crunch, and it first distorts then mutes any other sounds for the duration of the kick drum. Sound waves are additive, and if slammed into the rails, something has to give. In the picture you can clearly see how certain sounds completely disappear at times.

Excerpt from Green Day's "Wake Me Up When September Ends"

In Mr. Foti and Mr. Orban's article about what happens to a clipped CD when played through a typical FM air chain, they mention that due to phase rotation and non-phase linear filters, the clipped edges will not stay at the edge. They can in fact end up anywhere in the waveform, even right through the zero line. However, the detail that was lost in clipping is still lost, as evident from the next picture, showing the same moment in this Green Day song as it looks on the Composite Output of the flagship of one of the big processing companies:

Green Day on Typical FM

The carnage is painfully evident just by looking at it. Imagine what it sounds like on the air. The clipping damage from the CD is clearly visible at the output, nowhere near the edges, and the (previously undamaged) edges now have more damage from the FM processing itself. No wonder TSL is down! And we're still only at 2003.

Champions of the Loudness Wars Declared (but Metallica is supposed to be loud...)

Finally, the unequivocal winner of the loudness war.... everyone else, put your mastering chains down. The war has already been won, by Metallica's Death Magnetic album from 2008. Here's "The Day that Never Comes."

Excerpt from Metallica's "The Day that Never Comes"

And yes, Metallica is supposed to be loud. But the boys went a little crazy here....

You may notice how the lines aren't exactly straight. From what I've heard (read on the internet, so it must be true), the clipping was done during mixing, and the music was already a squarewave by the time the mastering engineer received it, so all he could do was to EQ it slightly (with a non-phase linear EQ), hence the slightly wiggly lines. He didn't have Undo, as it wouldn’t be invented for another three years.

That was the back story of why Undo is necessary. I figured the industry would come around at some point and start mastering properly again. However, they didn't, so out of equal parts sheer desperation and hunger for new music, Undo was born.

Undo is two parts. A De-clipper created by Hans van Zutphen (licensed for the Omnia.9), and a program-controlled multi-band expander, created by yours truly.

Together, they work to both remove distortion and undo compression. All on-the-fly, set and forget, with (almost) no effect on material that was properly mastered. Undo cannot repair every mistake, but it goes a very long way.

Here are more examples in pictures. Please note that the oscilloscope is zoomed out for the Post Undo shots. The lines are still at 0dB, but 0dB does not actually equal full scale here as the Omnia.9 has 48dB of internal headroom.

Metallica, after Undo:

Metallica with Undo

And Green Day, also after Undo:

Green Day with Undo

For more audio processing fun with Green Day, here's the composite output of the same song using the Omnia.9:

Green Day with Omnia.9

The original clipped edges (along with lost detail) are no longer evident in the output audio. The output, although obviously clipped in the FM final clipper, does not sound distorted, the detail is still there, as visible as it is audible.

Psychoacoustic Distortion Masking Clipping makes it possible! But, that's another article....

Disclaimer: I have no ties or inside information with the music industry. All opinions are my own, and in no way an official view of Telos, Omnia, Axia, 25-Seven or Linear Acoustic. My opinions are based entirely on listening to a lot of music over a long period of time.

Topics: Audio Processing