Thursday, 2 October 2008

DIY Mastering Part 5 - How loud is Too Loud ?

As regular readers of this blog will know all too well by now, I am firmly opposed to the so-called CD "Loudness Wars", where everyone tries to get their CD louder than anyone else's by pushing the recorded level higher and higher. This is ultimately a self-defeating process - the CD spec defines a mazimum recordable level, and the harder you push your music up against that level, the more squashed, flattened, crushed and ultimately distorted it gets. Meanwhile there is far less scope within the tracks on the CD for the contrast needed for a satisfying musical result.

BUT as a mastering engineer I spend a lot of my time lifting the level of people's music so that it can compete with the high levels of other CDs out there. And, as I've said in a previous post, I feel that this is actually a positive step for most albums.

How do I reconcile these two apparently contradicting views ? The answer is something I've also said several times before here:

Louder is Better, but Too Loud is Worse

By which I mean - every track (and group of tracks) has a "sweet spot", where it's loudness (and by implication compression, level, EQ etc) is just right. It sounds the best it can be. If it's not compressed enough, then quiet passages won't have enough presence, the mix may not "gel" or have enough impact, detail may be lost, and loud passages will make you wince. Whereas if it's too loud and compressed it can sound squashed and dull (meaning bland and lifeless, not lacking treble) and ultimately fatiguing.

If the idea of using compression on a mix surprises you, it's worth knowing that as a rule of thumb people tend to like quite loud, compressed music, especially for pop and rock. Rick Rubin, who produced Metallica's latest album "Death Magnetic" (currently being heavily criticised for it's excessively-squashed, distorted sound) said in an interview from 2004:

I wish I had examples here to play for you. If I knew we were going to talk about this I’d go through the library and find examples. Ultimately, if you listen on a car sound system or in the mainstream place where most people listen to music—cars, boomboxes sound systems you get at (chain stores), and if you “A/B” the less compressed version to the more compressed version, you pick the compressed version.

And he's right ! He also says, in response to a question about things sounding better on the radio:

Sometimes actually, if it’s too loud, it sounds worse on the radio.

And again, he's right. Sadly, this is exactly the case with Death Magnetic. Clearly this is a delicate issue, and one that even the most respected engineers sometimes misjudge. Music needs just the right amount of compression and level, based on the style of music and the original recording.

So, how loud is Too Loud ? Where do we cross the boundary from sweet-spot into overcooking ? The answer of course is -

Something is Too Loud when it starts to sound worse

But what is worse ? Everything is subjective. Rubin obviously thought Death Magnetic sounded good when he was working on it - perhaps he still does. Lars from Metallica has no problem with it, but I and many others think it's a great shame that so much distortion had to be introduced.

Loudness Measurements

Ultimately the only real way to judge this is to use your ears, but for what it's worth, here are a few facts and figures. I have analysed the loudness of several tracks using a free Mac utility called AudioLeak to measure their long-term A-weighted RMS level. RMS stands for "root mean square" and as applied to music roughly describes the loudness of a musical signal. A-weighting improves on this by taking into account the fact that the ear is less sensitive to bass and treble when judging loudness, and provides a better guide to how loud we think things. A track of equal "raw" RMS level but with more bass won't sound quite as loud, for example, and so will have a lower A-weighted RMS.

Here are some example A-weighted RMS level measurements, with raw RMS in brackets - they are long-term measurements, ie. average values over an entire track. The highest theoretical value possible is zero, and slightly confusingly they are measured down from there, so -10 is louder than -12, for example. So, with the loudest at the top, we have:

-8.6 (-6.2) Oasis - "Some Might Say": Severe clipping distortion
-8.9 (-4.9) Metallica - "TDTNC" (CD): Massive distortion & clipping
-10.4 (-7.7) Feeder - "Pushing The Senses": Heavy clipping distortion
-12.7 (-7.7) Metallica - "BB&S" (Mystery Mix): Slight source clipping
-14.0 (-10) Katatonia - "Consternation": Awesome (clean) sound, massive choruses
-15.3 (-13.1) Sugar - "Fortune Teller": From 1993
-21.8 (-16.9) Metallica - "TDTNC" (GH3) Needs to be louder !


There are plenty of interesting things to be seen looking at these numbers - firstly, the Oasis track actually measures fractionally louder than Metallica ! However by looking at the raw RMS values we can see that in brute power terms Metallica has a higher level - they just have more low-frequency in the sound than Oasis, so the A-weighted value doesn't reflect that. This higher raw RMS may also explain why the distortion on the Metallica tracks is even worse than on Oasis.

Looking at these tracks it would seem that with care the A-weighted RMS can actually be pushed as high as -12 dBFS without obvious distortion. Whether the result is satisfying musically, the numbers can't tell us, though. In my opinion the two best-sounding tracks here are Katatonia and Sugar - "Copper Blue" was a loud album for it's time, but look how things have changed. (By the way examining some SRT masters, the A-weighted RMS typically hovers around - you guessed it, -14 to -12 dBFS)

So, is the answer to "how loud is too loud" actually "any higher than an overall level of -12 dBFS RMS, A-weighted" ?

Well, if we're judging "too loud" to mean "the onset of distortion", then for guitar-driven rock music, yes, maybe. However other genres may suffer more or less and we need to bear in mind that rock is a highly compressed, distorted genre to begin with. I prefer a more dynamic sound personally, so I would pick a level closer to -14 - if it suits the music. Once again, at the end of the day we need to use our ears to make these judgement calls.

Understanding Loudness Measurements

It's also interesting to think about what these numbers mean. The Katatonia track is only 2dB (RMS) quieter than the "Mystery Mix" of Broken, Beat & Scarred", but still has more punch, weight and impact, to my ears. This difference is vastly more apparent comparing to the Metallica CD, and looking at the numbers we can see why. Katatonia has maximum RMS of -8 dB, in the track, compared to an average of -14, giving it a "loudness range" of 6dB.

Compare that with the "Death Magnetic" track. The highest raw RMS level in the track is -2.5 dB. But the average is an eye-watering -4.9, allowing it a range of only 2.4 dB. So the loudest parts can be only 2.4 dB louder than the rest of the track. Katatonia has almost three times the loudness range to play with. No wonder TDTNC sounds flat and lifeless by comparison, whereas when the chorus kicks in on "MyTwin" the impact and buzz it generates is huge. And with almost 10dB to play with, it's obvious why the Guitar Hero version has so much more punch and life - and in fact in my opinion, it would benefit from some EQ and being at a higher level and more compressed, to get it into the "sweet spot". This is why despite preferring the reduced distortion, some listeners still find it lacking.

Ultimately the decision about when the music starts to suffer at the expense of level is one of taste, and requires a judgement call by all concerned. However looking at RMS levels as we have here can be very revealing for a mastering engineer, so I strongly recommend you experiment with AudioLeak or another form of loudness metering - like all mastering facilities we use them constantly here at SRT when mastering. I also recommend you stick around the -14 dBFS A-weighted RMS level to ensure that your CDs are both competitive but also loud-sounding in their own right.

31 comments:

  1. Excellent blog as always! I'm learning more every time.

    Thanks, Ian!

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  2. Ian,

    Many thanks for the post.

    It would be interesting to compare the dynamic range of Death Magnetic to that of The Dark Knight soundtrack, one of the most exciting sounding CDs I've heard in ages.

    Also, do you think that moving from 16-bit to 24-bit media would have any effect on the Loudness War?

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  3. Hi Guys,

    You're welcome, gad you found it interesting.

    @Jonathon - Film soundtracks are mixed and mastered to conform to Dolby or THX specifications, which (if followed) mandate a much larger dynamic range than CDs.

    This, coupled with the fact that there won't be a band or a label pushing the engineer to overcook it, probably means the CD has a much better dynamic range than many mainstream pop-rock releases, and certainly DM.

    Most mastering and mix engineers, left to their own devices, do a great job !

    Ian

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  4. Good words, Ian, but if the conclusion is "trust your ears", I'm not sure how well that is going to convince people to change their practices.

    But it is certainly worth repeating that when people say they want "uncompressed" music, they almost always don't really mean it. :)

    You might be interested in a little project of mine, whereupon I took BS.1770, converted it to a time-varying loudness model, and shoehorned it into a program that estimates dynamic range across three different timescales. Runs on Windows and requires a rather large runtime install. Rather experimental, but it may give some more insight than a loudness meter alone...

    http://audiamorous.blogspot.com/2008/01/pfpf-experimental-estimator-of-dynamic_13.html

    It is certainly rather odd (and perhaps unfortunate) that loudness is being used as an estimator for both dynamic range and distortion, even though it is not directly related to them (although they do correlate). We'd be in much better shape if we had real dynamic range meters and real distortion meters. I'm hoping pfpf is one step towards that.

    @jonathan: 24-bit won't make a whit of difference. The differences in dynamic range that we're talking about would fit comfortably on a cassette tape. A lot of music would sound fine with only 8-10 bits of resolution nowadays. SRSLY!

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  5. Thanks for the explanation.

    Is there an ultimate solution to the Loudness War?
    Does the general public need educated as to what 'good sound'? Do we need much better sound reproduction from average equipment?

    Jonathan

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  6. I guess everybody knows "NAIM" sound systems. They have their own record company.

    They use a single microphone to do their records, and do the original mixes on the good old tape rolls lol.

    If you could get a demo CD, you would know what perfect music should sound like.

    But this is just for audiophils I don't think it's for rock fans like me :)

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  7. Has anyone got suggestions for the best way to increase the volume of the GH3 rip of DM (apart from turning the volume knob up)? I've tried Amplify with Audacity, without enabling clipping, but the resulting files still sound soft.

    Ian?

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  8. Hey! I really enjoy your articles about mastering. I interviewed Joe Satriani a little while ago, and some of the things he said about recording his new album might be of interest to you (if for no other reason than to demonstrate that Kirk Hammett certainly didn't listen to his former guitar teacher's views on mixing and mastering). One of his goals was to record an album that sounds better when you turn it up at home. http://iheartguitar.blogspot.com/2008/10/interview-joe-satriani.html

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  9. @Peter,

    Thanks for the link, it was a great interview! I got to see Joe play live in the summer and it was just the best gig ever.

    I've always thought that his albums sounded very big, open and dynamic. It's a real shame that other people don't follow his and John Cuniberti's lead.

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  10. @richard - Thought-provoking comments and blog, thanks ! Your loudness-measurement setup looks interesting, but I don't really 'do' Windows unless I absolutely have to ;-)

    Not wishing to appear smug, but I'm not sure there is really a need for better ways to measure loudness though - engineers are pretty skilled at this already. The problem is more to do with people ignoring these skills and pushing it too loud anyway :-/

    Which leads me to:

    @jonathon - My hope is that the Loudness Wars will end simply as result of exactly the current situation - customers complaining about the negative effects on sound. If the complaints eventually filter through, I would hope that people who currently think "louder is better" without exception, will have that belief challenged, and exercise caution as a result.

    @bernard - not to sound flippant, but you need a mastering engineer...!

    @peter, thanks for the comment and link, I'll check it out.

    Currently finishing a new blog post at the moment which may be about to throw the cat amongst the chickens again...

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  11. The hard part here is getting people to understand the problem. Most people simply can't hear the effects of clipping and compression. People dismiss my concerns as being no more than 'personal preference'.

    Why focus on Metallica? Here's a list of what I consider Expensive Coasters that I've bought in the last year or so, where the sound is so ugly that silence is preferable, and repeated listening just can't penetrate the wash of indifference the compressed sound creates.

    It's interesting to note that it's not just the major labels doing this:

    REM - Accelerate
    The Thrills - Teenager
    They Might Be Giants - The Else
    Matthew Sweet - Sunshine Lies
    Smashing Pumpkins - Zeitgeist
    Rilo Kiley - Under The Blacklight
    The Decemberists - The Crane Wife
    You Am I - Convicts
    The Rentals - Last Little Life EP
    The Cure - 4:13 Dream
    New Pornographers - Challengers
    Maria McKee - Late December
    Paul McCartney - Memory Almost Full
    Jens Lekman - Night Falls Over Kortedala
    Icecream Hands - The Good China
    James - Hey Ma
    Crowded House - Time On Earth
    Death Cab For Cutie - Narrow Stairs
    The B-52's - Funplex

    I honestly don't care if I ever buy a new cd again. I'm just consistently disappointed lately.

    Oh, i'd theorised the 'sweet spot' as being around -14 myself. Check out the b-52's 'Roam' for a clean, spacious sounding recording.

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  12. @HomeFrontRadio I agree, it's a tough one to explain. The "great" thing about Death Magnetic is how blatantly obvious the problems are. Almost anyone can hear the damage, and that gives a basis to explain what has happened.

    That's why I haven't "branched out" into criticising other albums, really. This keeps the issue clear and simple. What I've seen is once people hear and understand about Death Magnetic, they start hearing similar problems elsewhere,w ithout me pointing them out.

    Also, writing about the problems with excessively high-level albums doesn't really interest me so much - there are many other issues in mastering that are much more important and interesting, I think !

    Having said that, if people want to "Name and shame", head over to JusticeForAudio.org, where people are doing exactly that...

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  13. I'd prefer -15/-16db as the MAX cut off limit for the avg loudness of a song,be it cd's,sacd's or dvd-a.
    Anything above that should be unacceptable.

    PS:I've maximized the volume of the day that never comes from -21(which is way too low for a metal song,to around -17,WITHOUT clipping or limiting,and it sounds brilliant.

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  14. coming a bit late but thank you a lot for this article

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  15. Best post of the five! Keep up the great work!

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  16. Thanks Lee, glad you found it useful ! If you enjoyed that post, you might also like this one:

    How to avoid over-compressing your mix

    From my other site.

    Ian

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  17. and i thought -24 db was a good number for an average audio level!

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  18. This comment has been removed by the author.

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  19. Awesome job, great advice! I wrote an article about the loudness war a while ago, and how to avoid it by using RMS to find a "starting spot" in the mix. You might find it interesting. http://www.dayinthelifeofacommercialmusician.com/2013/01/the-loudness-war-how-not-to-be-casualty.html

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  22. whooooohooooo, more sketches!!!
    they all look awesome, i like the crazy lizard on a strange howersomething guy the most:)

    and thank you so much for the comment on my dreamscape entry, i will post the final soon, and i would really like to hear your opinion :)

    keep it up man!
    Vanja










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