The secret of maximum loudness (part 1)

The secret of maximum loudness (part 1)

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00:08
hi and welcome back apologies for the slightly click-baity title but yes there really is a secret of maximum loudness and it works regardless of the genre the medium or the platform obviously i'm not going to give it up yet you'll have to keep watching because we need some background to properly understand it i remember when i got my first little stereo system as a child thinking that the volume control set in absolute loudness for playback [Music]
00:41
when i started using my dad's hifi to copy vinyl records onto cassette i discovered that the record level could make a big difference set it too low and my copy would be really quiet and buried in noise but set it too high and i'd get horrible distortion with some material i noticed that pushing the levels a little into the red actually made it sound better but that's not the subject of today's video the point is while you had a little leeway to choose how hot you printed to tape the nature of the medium dictated that
01:16
most material sat around the sweet spot where you get the best signal-to-noise ratio with the least distortion when digital audio was invented it was originally assumed that people would continue to work the same way the nominal unity level of analog recording would be equivalent to minus 18 or minus 20 dbfs with the extra dynamic range reserved for headroom but of course with digital audio that headroom is just as clean and linear as the rest of its dynamic range there's no distortion penalty for pushing the
01:47
levels right up to full scale you just get a louder master so that's what people did and then people discovered that actually you could push the levels a little bit further and deliberately clip the converters and that this clipping would be inaudible if it were brief enough or might even sound subjectively good and then the first digital brick wall limiters came along and the loudness war really got going in earnest now you could push those levels harder and harder
02:18
and it wouldn't clip it would just get louder and suddenly everyone was trying to be louder than everyone else let's pause here to discuss the elephant in the room [Music] yes louder is better at least until you approach the pain threshold anyway below that every decibel of extra loudness will translate to perceived extra clarity extra solid bass more detail more depth more width whatever emotional
02:48
impact the music has at a low level it will have more of it when turned up louder but real loudness is not the same as artificial loudness real loudness takes the whole waveform and scales it up assuming you're not damaging your hearing this is a good thing real loudness is why a live gig can be so exciting the natural uncompressed dynamics of a drum kit augmented by a good pa system provides a visceral experience that you'll never recreate with a hi-fi
03:17
system and a studio album artificial loudness as created by a brick wall limiter is not the same increasing the average levels makes the audio seem louder but the peaks are now smashed down into the body of the mix and this has consequences not surprisingly this can reduce the impact of your transients making them less punchy or snappy but there are also more subtle side effects such as a loss of depth and space while real loudness can fill a room and immerse you in the music artificial
03:52
loudness forms an oppressive wall that pushes you back in your seat perhaps most egregiously reducing the peak to average ratio can suck the life out of a mix making it flatter more boring less exciting if it's an upbeat energetic rock song this is perhaps the worst thing you can do the listener won't know why but the music simply won't be as exciting as a classic rock mix with the dynamics intact of course at this point i'm obliged to point out that we've come a long way
04:24
since the first brick wall limiters were released when limiters have become much more sophisticated and powerful pro l2 with its modern limiting style can smash a mix really hard yet still retain a remarkable sense of punch and definition [Music] but no amount of clever program dependency can change the fact that you're reducing the relative size of the peaks and filling in the gaps between them a
04:57
clever person once said that music is the space between the notes removing or reducing the space between your transients risks sucking some of the musicality out of your mix however when used carefully a limiter can make the audio significantly louder with no negative impact at all and usually significantly louder still with only very minor side effects so this leaves us with a dilemma if we don't use any limiting at all our mixes will play back much quieter
05:30
than the majority of other releases of course your listener could just turn it up hold that thought because we'll come back to it but you'll worry quite reasonably that they won't and your mix will just end up sounding weaker than its peers but on the other hand competing with the loudness levels of many modern releases is also going to make your mix sound weaker than it potentially could so what's the optimum loudness to aim for when mastering or to put it another way at what point
06:02
is the benefit of the extra loudness outweighed by the disadvantage of a low peak to average ratio well we need some way to quantify loudness in order to answer that question so i'm going to have to talk about metering how we measure the loudness of a signal which is more complicated than you might initially expect let's start with the channel meters in a daw these are quite simple they flip the negative half of the cycle to positive then display the sample values on a decibel scale of course the signal is continually
06:32
oscillating through zero and the meter would be unreadable if it showed that so the values shown decay slowly to smooth out the dips and display this sine wave as a constant level hence if the sine wave stops suddenly the meter nevertheless decays gradually this is perfect when you're tracking vocals and you need to know how close you are to clipping but it doesn't cut the mustard for mastering for a couple of reasons the first problem is that this meter just reads maximum sample values but when this signal is converted to analog
07:04
the original curvy analog signal will be perfectly recreated and it's normal for the peaks of the analog signal to be in between samples and higher in levels than the sample values either side measuring the actual peaks of the waveform requires a more sophisticated true peak meter that calculates values in between samples more on this later perhaps more significantly however peak metering and also true peak metering tells us almost nothing about how loud the signal will sound this is partly due to the nature of
07:36
human hearing it's not flat in frequency response so a sine wave at 2k will seem much louder than a sine wave at 200 hertz [Laughter] even though both have the same peak levels also a long burst of two kilohertz will seem much louder and more obnoxious than a very short blip even though both are again at the same peak level a more real world example would be drums and distorted electric guitar
08:07
if i normalize these to the same peak level the guitar completely obliterates the drums the drums need to peak at a significantly higher level than the guitar for the two to sound balanced because of the shorts might be transients in the drum track finally peak levels don't really mean much anyway the easiest way to demonstrate this is with a sawtooth wave here's how that looks on pro q3's analyzer with a low fundamental
08:38
plus a harmonic series above it each of these harmonics is essentially a separate sine wave now i'll add a high pass filter i'll start with it set way too low to have any audible effect on the sawtooth wave but notice the peak level is already reading 2 db higher than it was now let's start to wind up the filter cut off until it starts to shave away the level of that lowest partial i'm sure you'll agree this doesn't sound louder than the unfiltered version
09:10
and yet the peak level of the filtered version is a full 6 db higher than the unfiltered version if you've ever wondered why an eq cut or subtractive filter can make your mix apparently get louder this is what's actually going on phase shift has caused all the individual partials to add up differently and the peaks of the wave have got higher as a result but it's not actually louder in any real sense so measuring the peak levels is pretty much useless when trying to determine
09:40
how loud something will sound that needs a different approach and there have been a few over the years the classic vu meter relies on the physical ballistics and inertia of the needle to smooth out peaks and display more of an average level instead this is much better than a simple peak meter but you need a little practice to interpret what a vu meter is telling you especially when it comes to signals with lots of low frequency content which tend to pin the meters even at perfectly sensible levels
10:10
[Music] another approach is to measure rms levels or root mean squared without delving too deeply into the maths involved this averages out the levels over time mean being simply a more mathy way of saying average this solves the problem of phase shift inaudible changes in phase will not cause changes in rms levels and our sawtooth wave doesn't read higher when i high pass filter
10:45
it also potentially solves the problem of duration as we're averaging the signal levels over time but the question is how much time if you average levels over a short 50 millisecond window you'll get a much faster moving bouncier reading than if you average over 500 milliseconds [Music] or two whole seconds with longer larger windows rms levels correlate quite well with perceived loudness but we still have the same problem as vu
11:16
meters with bass heavy signals that tend to read too high [Music] so some meters use weighting to try to emulate the non-flat frequency response of human hearing basically this means a filter to boost the upper mid-range and cut the low and high extremes so the meter responds more or less respectively this is a standard a weighting curve as used for measuring
11:46
environmental noise levels i told you measuring loudness was more complicated than it seems but we do have a better option these days thanks to the broadcast industry which has developed a new standard way to measure loudness with a new unit of measurement known as loudness units or lu for short this new scale is based on rms style averaging but includes frequency weighting to avoid the problem of over reading bass heavy signals and also defines the averaging window
12:19
used in fact it defines three different ones called momentary short term and integrated momentary averages signals over 400 milliseconds and gives us this relatively bouncy display labeled m in pro l2 short term uses a six second window and provides a much steadier reading but doesn't move much in response to drum transients this is the most useful measure of how loud is the signal at this point in the
12:50
song the integrated reading is a little different this averages out the levels over the whole song or the whole album or whatever you want to measure in pro l2 you can click to reset before the start of the song and by the end of the song or the end of the album you'll have a single integrated loudness value for the whole thing [Music] your daw or audio editor might also allow you to analyze clips offline to calculate an integrated loudness for
13:22
the whole clip this might seem like a perfect way to quantify the loudness of a song but it does have one flaw which i can illustrate with led zeppelin here's immigrant song i won't play it to avoid copyright strikes but i'm sure you know how it sounds it kicks in hard and rocks hard all the way through [Music] now compare this with stairway to heaven this starts off famously quietly and builds gradually all the way through as a result
13:54
this mix has a lower integrated loudness than immigrant song even though the climax at the end is about the same so actually the best way to derive a single loudness value for a song might be to isolate the loudest section typically the last chorus and measure the integrated loudness of just that section failing that watching the short-term reading during that section will do just as well [Music] note that loudness units correspond to decibels
14:25
if a mix has a loudness of -16 lufs and then you turn it up by 3 db it will now have a loudness of -13 l ufs which helps to keep things nice and simple so now we have a way to measure loudness you doubtless wants and numbers what loudness readings should you be aiming for should you even have a target level and does it need to be different for different platforms or formats [Music] well we'll get to that in part two along with the secret in the title
14:59
of course thanks for watching you

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