8 Music Mastering Techniques to Make Your CDs Sound Better

How can you make your CDs sound as good as possible ? 

By "mastering" them - meaning, by balancing each individual song against the others in level and sound to create a coherent, satisfying whole.

Many of my posts are squarely aimed at people who want to get as close as they can to having their CD mastered by a professional. However these tips and suggestions are more general and will benefit anyone who wants their CD to sound good - they apply equally, regardless of the level or standard of your mastering skills.

1. Think big - Mastering is about making an album from a collection of songs. Now isn't the time to agonise about the details - whether the vocal is too high in one song, or whether you should add another guitar part to another. Mixing is over - move on ! Think about how songs relate to each other, look for a "line" through them, so they flow convincingly. I often describe mastering as finding the "centre of gravity" of a collection of tracks, and helping them all sit right next to each other. Listen to the overall sound of each song, and work on that.
   
2. EQ and volume are everything - The equalisation (broadly speaking the bass, middle and treble balance) of each track needs to be right before anything else will work. To choose the right EQ, the level needs to be right, but the EQ influences what level you choose. Sounds like a Catch-22 ? It is. So, set the level, adjust the EQ - repeat until happy. Of course dynamic compression is a crucial part of this process - see below.
3. Have an open mind - Normally my advice to people is "don't try to master your own stuff". If you are trying to do it yourself though, throw away all the pre-conceptions and ideas you have inherited from the recording and mixing process, and start afresh. Be prepared to cut swathes through all the detailed decisions and reasoning you've put into the project so far - a mastering engineer gives an impartial, third-party opinion about what's best for your material - you need to try and do the same. Listen to the Big Picture.
   
4. Match vocal levels - When choosing how loud each song should be compared to the others, it's easy to get confused. A great rule of thumb is to balance the vocals. If you can get the vocals for each tune to sound as if they're in the same ballpark, almost anything else will work around them. Where you don't have a vocal to listen to, pick the main melodic element instead.
5. Work fast, be bold - Use broad brush-strokes; listen to each song and make big, instinctive changes. Set the level, choose an EQ and go for it. Instinct is important in mastering, and often your first thought is the right one. If you find yourself going around in circles worrying about the details, it may be best to move on to a different song and come back later.
   
6. Keep it Dynamic - You can master a CD without boosting the overall level at all, and all the EQ and level adjustments will still be invaluable. However most people also want to lift the overall level to be closer to commercial releases as well, and so compression and limiting become important parts of the process. I'm writing a whole series of posts about this, but the main point to make here is - don't be tempted to over-cook it. Music needs light and shade - without Quiet, there can be no Loud. So strive to find the "sweet spot" for your album, where the benefits outweigh the problems compression and limiting can cause. If in doubt, check out my post How Loud Is Too Loud ? Don't let your CD be a victim in the Loudness Wars - no-one wants to be the next "Death Magnetic"...
7. Good gaps - mix it up - The silence between tracks on your CD can sometimes be as important as the tracks themselves. If a gaps are too short, the album can feel rushed and exhausting - too long and the listener is distracted form the flow of songs wondering where the next tune is. Some people swear by two-second gaps, but my favourite rule of thumb is - make the gap equal to two bars of the out-going song. Times to consider breaking this rule are early on on the album, where you might want to build momentum, or after a song with a slow fade. Occasional longer gaps can give the listener time to catch their breath, or frame a change of mood or style, for example. Variety is the key here.
8. Burn Slow, Burn Steady - So your songs are sequenced, balanced, boosted and spaced - all you need to do is burn a quick copy at 52x and listen, right ? Wrong. Different brands of CDRs work better in certain burners than others, and error rates vary widely depending on the write speed. Yet again this is a complicated topic, but on the whole we see the best results burning at slower speeds like 16x, 8x or even 4x. This isn't such a big issue unless you want to use your CD for replication, but avoid the very high speeds, and spend a little more on "name" brands like EMTEC, TDK or Verbatim. If you want to use what we use, these brand-names are no use, though - the company widely-regarded as producing the most reliable CDs of all is called Taiyo Yuden - but not all suppliers can offer them.

If your goal is to try and get a professional result for a CD release, all the above techniques will help you. You'll also need decent monitoring in a reasonable room, and probably to read all my other DIY mastering posts - but you'll find the ideas here equally valuable, even if your goal is only to make your band's demo sound as good as possible, or you just want to make a better-sounding mix tape.

I hope you find them useful, let me know how you get on trying to put them into practise.

 

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.

Mastering Techniques - Using A Compressor - Part 2

This is Part 2 of a series of posts about using compression in mastering - the first post is here. For a more general introduction to using compression, click here.

Choosing the right compressor settings

Now your ears are focused on what the settings are doing, where should you set them ? Easy:

Adjust the controls until it sounds right

OK, that's next to useless, I know. "What sounds right" varies on the instrument or mix, the genre and taste. There is also a big difference between compressing an instrument in a mix and compressing a whole mix.

Compressing an instrument

For example, compressors are commonly used to even out very dynamic (spiky) intruments in a mix, like a snare drum, say. A snare note has a big spike at the beginning (the transient) created when the stick bashes the skin, followed by a longer sustained sound as the body of the drum resonates. If you push this uncompressed signal too high in the mix, the initial transient may start to sound annoyingly loud and percussive or even distort, if you push it into the red. As a result you can't hear enough of the "thump" of the drum to give it weight and impact.

To minimise this effect, you can compress the signal, using:

• a fast attack time - as soon as the signal starts to get loud, the compressor quickly starts to take effect
• a high ratio to have quite a dramatic effect reducing the spiky transient
• a fast release time to allow allow the compressor to "relax" quickly once the spike has been controlled
• a fairly high threshold so the ring of the drum is not compressed as well as the transient

With a little tweaking, the result should be a much fuller, punchier snare sound - the compressor jumps in quickly (fast attack) and holds back some of the big spiky transient (high ratio high threshold) but because the spike is very short, quickly releases again to allow the main note of the drum to sound. Overdoing it will have undesirable results though - for example if the attack time is too fast, it will remove all the attack from the note, making it sound dull and lifeless. But a bit of experimentation will soon sort this out, and as a result, the snare can be lifted higher in the mix without becoming annoying or distorting - the compression makes it louder. It also sound fuller and punchier, as a by-product.

Compressing a mix

Using settings like the ones above almost certainly won't work well on a mix, though. As a rule in mastering, the aim is for the compression to be as unobtrusive as possible. Usually we aim for a natural-sounding result, where the compression isn't easily noticed. Most final mixes have already had suitable compression used on the individual instruments, so the settings described above will probably result in something that sounds squashed and lifeless, or even pumping and distorted.

Remember in what follows that it's very common to use both a compressor and a limiter when mastering - the limiter catches the very fast transients, allowing the level to be lifted even further, but I'll discuss limiters in the next post. As far as compression goes, for a whole mix I often:

• Avoid very short attack times - and very long ones
• Use shorter release times
• Use low ratios
• Avoid large amounts of gain reduction

The medium attack time allows percussive elements of the mix to punch through, but still controls the overall signal level. If this gets too long, you'll hear the "thump-suck" effect I mentioned in the last post. Shorter release times also avoid obvious pumping, but you need to be careful. If they get too short, there won't be enough control and you may hear the compressor "bouncing" - rapidly triggering and releasing over and over, sounding crunchy or distorted as a result. Low ratios and moderate gain reduction avoid the compression becoming too ear-catching. Time for another rule of thumb:

If you compare the compressed signal with the level-matched original, it should sound better

Meaning not squashed or pumping (unless that's what you want !). You should always level-match the "before" and "after" levels before making your comparison, of course. When level-matching for comparison purposes, it's often worth using the vocals to judge the loudness. Our ears tend to latch onto a voice as the most important element in a mix, so get these as close as possible before comparing. Then listen and ask yourself questions like:

• Which do I prefer ?
• Am I sure one of them isn't louder ?
• Have I achieved what I wanted ? (ie. made it punchier, fuller, with more impact & excitement)
• Does the compressed version still sound lively and exciting, or is it too squashed ?
• Does it sound closer to similar tracks I'm trying to emulate ?
• Can I hear more of the quiet details in the mix, or is it getting "mushy" and confused ?
• Does it still sound natural ?

If you can answer these questions with a positive, you're doing well. If not, try varying some the settings and comparing again. If you still can't get a result you like, try a different compressor - or maybe it doesn't need compression at all.

All of this is very hard to describe in words of course, but hopefully by now you'll have a better idea of how compressors are used, what the controls actually do and what you should be listening for.

If you found this post useful you might also like to watch my free webinar on the more advanced technique of multi-band compression - for more information, click here.

 

Mastering Techniques - Using A Compressor - Part 1

There are still more things I want to cover in the area of general DIY Mastering, but I've decided it's time to start posting some specific information up here to help people get to grips with common mastering techniques. So this is the first in a new series of posts headed "Mastering Techniques", which will run alongside the DIY Mastering posts. I'm going to cover things like level-matching, EQ, stereo width adjustment and so on, but I think the subject most people struggle with is compression. Often people have been told that the answer to any number of problems is compression, but don't know what they're trying to achieve, or how to get there.

This post started to get much too long, so I've decided to split it into several sections, this is Part 1...

Know What You Want

In my opinion, the most important thing when using compression is to have a clear goal. You'll see lots of explanations of compression saying things like "a compressor reduces the dynamic range of it's input", but I don't find these very intuitive, and prefer the explanation I was given as a trainee:

Compression is used to make things louder

There can be all kinds of positive side-effects of this process, like making things sound fuller, richer, more controlled or punchier, but at the end of the day, especially in mastering, it's all about loudness. NOT excessive loudness, but something musically beneficial.

Mastering engineers almost always use a limiter somewhere to boost level, but the problem with this is that mixes very quickly sound crushed or distorted using only limiting. Using some gentle compression first means the limiter doesn't have to be hit so hard, giving a more natural sound. More on limiters in a later post.

The ideas here apply equally to compressing individual instruments or voices in a mix, incidentally, but you'll need different settings, usually. First we need to recognise a harsh fact of life:

Not all compressors are created equal

The best analogue compressors cost thousands of pounds. However there are some really good software plugins these days which cost far less. For example if you're looking for emulation of a traditional analogue compressor in a mix, complete with "musical" pumping, I really like Sonic Timeworks Compressor X. Would I use it for mastering ? Probably not. However there are high-quality compressors available on a DIY budget which are suitable for mastering - the TC Electronics System 6000 is a mastering "industry standard", and many of it's algorithms are available as plugins for their Powercore system, for example. Many people also use plugins by Waves or Izotope, and discussions rage about whether it's really possible to master with something so cheap, and which is better, on the Sound On Sound mastering forums and elsewhere.

Regardless of which compressor you decide to use though, they all share similar controls and concepts, and at the end of the day it comes down to whether you're happy with the result you get. With that in mind, lets dive in:

Exploring Compressor Controls

Try this experiment - we're going to overdo everything to begin with, so you get a feeling of what the different parameters do:

• Choose an instrument to compress and solo it (We'll move on to compressing a whole mix later)
• Patch a compressor across the stereo master output channel of your system
• Start with a ratio of 2:1.
• Set attack and release times of 100ms, if possible. You may have to disable "automatic" options first.
• Gradually reduce the threshold until the meters show you 4 or 5 dB of gain reduction

One of two things will have happened. Either:

• The sound will have got quieter, because the compressor is holding back the louder peaks. In this case you need to add some make-up gain, sometimes called output gain. Adjust it until the sound is a similar volume to when you hit the bypass or disable switch

Or:

• The sound will already be at a similar level, in which case your compressor automatically boost the output (make-up) gain

Now toggle bypass on and off and listen to the difference. Depending on your material, you will hear more or less difference. If you can't pick anything out initially, increase the ratio to 4:1 or reduce the threshold until more gain reduction is happening. (If you can't hear 6dB gain reduction with a ratio of 4:1 you should probably get your mastering - and probably mixing too - done by someone else !)

If your compressor has automatic attack and release times, it will probably sound OK (but a bit squashed). Even with manual controls, it shouldn't sound too bad. Once you can clearly hear the difference between the bypassed and compressed signals, you can try and figure out what it is you're hearing.

All the controls interact to give different effects, but before we get to that lets look at each in turn. First, ratio and threshold.

Ratio

Try increasing and decreasing the ratio. Higher values (4:1 etc) cause a more exaggerated effect - the compression "hits harder". Lower values are more subtle. If your compressor doesn't have auto make-up gain, you'll need to adjust it to match the bypassed version for a clear comparison. As a rule of thumb, use a high threshold and high ratio for a hard-hitting sound, but watch out for unnatural results. Lower ratios give a softer, "warming" or "thickening" effect. I rarely use higher than a 2:1 ratio.

Threshold

The threshold control determines when the compressor starts working. Lower values will give more compression, higher values give less. A low threshold with a high ratio will give lots of hard compression and probably sound very squashed and lifeless, whereas a higher threshold and low ratio will be a much more subtle. Whatever values you decide on, there is one rule of thumb worth remembering:

If the gain reduction meter doesn't return to zero several times a bar, you're almost certainly using too much compression

- because this means that the signal is being compressed all the time, and will probably sound flattened as a result. Try a higher threshold, and then higher ratio if it's not doing enough.

Attack & Release Time

Since I specified long attack and release times, you will probably hear the sound being "snatched" away right after a new note comes in, and perhaps "pumping" back up afterwards. Sustained notes are a good way to hear this. If you increase the attack and release times you'll certainly hear these effects. (For a deliberate example of this classic "thump-suck-relax" pumping listen to "One More Time" by Daft Punk). Automatic or "intelligent" settings reduce this effect, but increase the risk of using too much compression without realising it.

Now try reducing the attack time to it's minimum value. The sound will probably duck very quickly away to begin with - perhaps too fast to hear it happen, followed by the longer release back up to full volume. The chances are it will have lost any impact it used to have, especially with a higher ratio, and sound quite unnatural. Reducing the release time decreases the "pumping" effect, but as you get too short will start to sound "crunchy" or distorted.

Now your ears are focused on what the settings are actually doing, where should you set them ?

Answers in the next post.

DIY Mastering Part 4 - Mastering Speakers and Monitors

The most important tool a mastering engineer has (apart from his ears and expertise) is the monitoring, meaning the speakers, amps and converters. We debate all of these at great length between ourselves, in online forums and down the pub, but without question the speakers have the greatest impact on the sound. (They need to be well-placed in a decent treated room, but I already covered that in my third DIY post.)

This post won't enable you to choose a set of speakers by reading specifications or manufacturer's blurb, but hopefully it will give you an idea what you should be looking for, and why.

So, what are suitable speakers for mastering ? Well for example we have B&W Matrix 801s in Studio 1 at SRT, Genelec S30Ds in Studio 2 (In general I don't rate Genelecs, but the S30s have a ribbon tweeter and are in a class of their own). Other common names include ATC, PMC and Dunlavy. What all these monitors have in common (apart from costing at least as much as a large family car !) is that they have:

1. Flat, or neutral frequency response - meaning their response is very even over the whole audible range. So, for example, B&W 801s come with a graph measuring their response - it only varies by +/- 1 dB from 20 Hz to 20 kHz.
2. Acurate phase response - meaning that the stereo image is very detailed, giving an absolutely solid mono center image, but also a deep, convincing "three-dimensional" soundstage - at least, on a decent recording. The stereo imaging in our studios is so good that it's common for people to ask if some of the sound is coming out of the center speaker (used for surround work), even though they are listening to pure stereo. And on the occasions where a mix element is accidentally phase-reversed, it leaps out and draws attention to itself.
3. Clean, controlled dynamics - with only minimal distortion introduced, even at high listening levels. (Using a suitable amp is important for this, too, of course.)

Of course there are many other aspects of speaker's capabilities I could list, but it's almost more important to realise that these characteristics mean mastering speakers should be:

1. Revealing - allowing you to hear details you'll miss on other speakers - faults, like clicks, hiss and distortion; but also the positive sides of the recording - accurate stereo imaging, "depth" (meaning the impression of a three-dimensional sound field), impact and dynamics. Listening on a mastering system should almost be like wearing headphones, in this respect.
2. Clinical - Mastering speakers don't make things sound good. Unlike speakers for tracking or mixing, they shouldn't add "vibe", or "feel". Often they might be described as "bland", "boring", or at best "civilized". In fact, they are reliable and acurate. Only the very best recordings will sound good on them ! In fact that leads us neatly to:
3. Unforgiving - It's often shocking to hear how bad many recordings sound on a mastering rig - the uncompromising accuracy uncovers limitations masked by lesser reproduction systems. While this won't necessarily make for a very satisfying listening experience, it's essential for the mastering engineer to hear and correct any problems or limitations in the original mix.

Together, all these requirements add up to help the engineer achive translation - when it sounds it's best on the mastering system, it will sound great everywhere else, too.

So, if you've got this far, you're probably thinking "how the hell do I choose speakers which meet all those criteria ?". If you can't rely on printed specifications alone, this is a tough question. Until you're learnt exactly what a recording should sound like, it's hard to recognise a pair of speakers that make it sound that way.

Probably the first piece of advice is to get some recommendations. This post was inspired by a thread on the Gearslutz mastering forum asking about mastering speakers, and places like this or the SOS forums are good places to start - perhaps less than £500 isn't really realistic, though! Several of the speakers I mention above are available second-hand for "reasonable" amounts of money. My personal favourites, B&W, have ~35 staff working constantly on research and development, and the advances they make for their most expensive speakers always filter down to the cheaper models. I have Series 2 601s at home and am frequently amazed by how good they sound. Not that I'm suggesting you use them for mastering, but considering the difference in size and price, there's almost certainly something in the 600 range to suit.

Next - listen ! Find a showroom where you can test a few different speakers, ideally in the same room, and listen to various different tracks you know well. Even better, get some on demo and try them in your room. Remember you're looking for accuracy, not excitement - mastering monitors reveal limitations that others don't. Choose a range of recordings and be objective. "Sledgehammer" by Peter Gabriel is a great-sounding track, but it has very tight, controlled bass, so if the speakers give it a thundering bottom end, they aren't flat. "Dummy" by Portishead is a classic album, but it's almost entirely in mono - that should leap out at you. Maybe even take a CD with a few test-tones on it - for example a sine wave sweeping up from 20Hz to 20kHz will not only give you an idea about the speakers frequency response, but may also reveal a few buzzes and rattles along the way. (Don't play it too loud, though, or you may find yourself paying for some blown tweeters...)

Finding the right speaker in your price-range is a major challenge for a would-be DIY mastering engineer, but once you've worked with truly acurate monitoring for a while, you won't want to go back.

DIY Mastering Part 3 - Room Acoustics, Treatment and Layout

This is too huge a subject to cover properly in a blog, but if your monitoring environment isn't working well, you'll never be able to make good mastering (or mixing) decisions, so before you start considering tools or techniques, you'll need to get the room working reasonably well. Here I'll try to give some short but useful pointers and links to good, more detailed information.

The Room:

1. Needs to be a decent size - at least 3m x 4m, say.
2. Needs to have good proportions. Square is bad, a rectangle is better unless it is twice as long as is wide. All shaped rooms have "nodes" - certain frequencies which are emphasised or minimised by reflections between the walls. The dimensions of the room determine which frequencies will be emphasised, and the goal is to spread these nodes out as much as possible, to give the most even response. There is a great free utility called ModeCalc which allows you to calculate the room nodes for a given room, and the same page has a great introduction to the subject. Ideally, you could build "splayed" plasterboard walls to give a wedge shape which reduces the nodes even further.
3. Needs acoustic treatment. Every room will benefit from some acoustic panels - you can make these quite simply yourself using high-density fibreglass ("rockwool") mounted in wooden frames, or buy them from a company like RealTraps, who run the site that the ModeCalc utility is hosted on. These "bass traps", or more accurately "broadband absorbers", will further even out the frequency response of the room, enabling you to make better mixing and mastering decisions. Foam panels may also be helpful but are far less effective, especially in the bass end, where rooms have the most problems. Egg-boxes are useless !
4. Needs the speakers in the right place. They should be on a shorter wall, not too tight into the corners, equally spaced from opposite walls. I've seen several very theoretical methods of determining this, but perhaps the best advice is to get a recording you know well, play it at your chosen reference level, and move them around till they sound "right".
5. Needs a good listening position - equally distanced from both speakers, obviously, but not in the middle of the room. Whatever the shape, some bass frequencies will cancel most strongly in the middle of the room, so it's almost always a bad mix position. If you are one third of the room length away from the speakers, you'll be off to a good start.
6. Needs the right materials. For example, Pro studios use very expensive acoustic panels to control the sound by reducing unwanted reflection from smooth plastered walls. A cheaper alternative is to put carpet on the walls, with the idea of "deadening" the sound. However this isn't always a good idea in a mastering room - since the idea is to get the best possible result for a "normal" listening environment, a certain amount of reflection in the room is important, otherwise you'll be tempted to add too much high frequency to everything. Heavy curtains are probably a better idea for controlling the "liveness" of the room, not least because you can easily change their arrangement and effect on the sound in the room.

All of the factors above affect the way your room sounds, hopefully for the better ! In a later DIY post I'll describe a few simple tests to help you check if your room sounds good.

DIY Mastering Part 2: Before You Start

Before getting into more detail, there are some ground rules to be covered. All of these are important guidelines for any mastering engineer. I'll spread them over a few posts, but we'll start with rules for before you start mastering.

1: Always use a fixed listening environment

Which means level, room, monitors - the whole thing. Mastering is the art of turning a collection of pieces, songs, tracks, into an album. (Or single, or EP...) We're trying to judge impact, pace, atmosphere, dynamics and timing ( amongst others ) - in fact, as a professional mastering engineer I'm almost trying to second-guess the artist. To make a fair and accurate judgement compared with all those other discs, we have to be 100% confident we know what we're listening to, which means eliminating variables in the listening environment. The same goes for any room used for mastering - it needs to be as good as possible.

I'm going to cover room acoustics and treatment in a later post, but the first and most significant thing to control is the level - ie. how loud you listen to the music. I have two levels I master at - one is 12 dB below the other, and I switch between them throughout a session. The exact level you use isn't critical, but it needs to be consistent. (For the technically minded, use an SPL meter and generate pink noise at -18 dBFS. In my room this corresponds to a C-weighted SPL of 79 dB SPL.)

Then listen long and hard to some good CDs. Figure out which ones you consider to sound perfect, which ones sound too loud, which too soft, which too bassy, which too bright. You might decide to use a slightly higher or lower level than I've suggested to suit your comfort or taste, but there are very good reasons for sticking close to this reference level.

You'll probably find that a large number of recently mastered "classic" albums sound absolutely fantastic at this level, and also that many of the newest sound uncomfortably loud - check out my first DIY post for more about loudness.

Once you've settled on a level - stick with it. If you work at it for long enough you'll develop an instinct for the perfect level for any piece of music, and more importantly you'll avoid being tricked by the Fletcher-Munsen effect; in a nutshell, quiet sounds appear duller and thinner - ie. if you master with your level too low the chances are you'll add too much bass or top, and vica versa.

2: Use full-range, FLAT monitors

A CD is capable of reproducing a frequency-range of 20 Hz to 20 kHz. Your monitors need to come close to this - anything they can't reproduce, you can't hear, and may misjudge. In a pro mastering room this generally means the monitors will be big, and expensive. (In most mastering-houses they may easily cost more than a family car !) So try to choose neutral, accurate speakers, with a flat frequency response - perhaps bland-sounding to some ears, because that way you know it's the music that sounds great, not the monitoring. B&W make some superb hi-fi speakers which could be suitable for DIY mastering.

Ideally you should master on different monitors than you mix on, and even in a different room. This is partly to get a fresh perspective on what you're listening to, but also it means that if there are problems or limitations with the monitors you mixed on, you are more likely to spot this. If you're going the DIY route obviously this won't be easy, but the next best thing is to listen to your mastered audio in as many different places as possible. If it consistently sounds boomy, it probably has too much bass. But problems that you only hear on one system are more likely to be to do with the setup of that system.

One good tip is to setup your home stereo speakers in the mastering room, assuming they're decent quality - since you listen to most of your music on these, you may be much more sensitive to mastering judgements listening to them. Even listening on a favourite pair of headphones can be useful. But remember the golden rule - pick two mastering levels (three at most) and only use these when mastering.

3. Use a loudness meter

As I said in my first DIY post, perhaps the most important thing a mastering engineer does (apart from put the right tracks on the CD, in the right order !) is to choose a consistent, musical level for each track. The most important tool for deciding this is your ears, but meters giving you an objective measurement of the level are invaluable. Most people will probably find it easier to use the digital metering offered by a piece of software, but I still have a soft spot for the analogue needle, or VU meter.

Whichever you decide on, the most important think to know is why bother to use a loudness meter ? Because the absolute and relative loudness' of tracks on an album have an immense effect on their perceived sound and a peak meter is virtually useless for judging loudness. The classic example is the human voice - a very quiet voice can have an extremely high peak level. It "looks" loud on a digital meter, but it sounds quiet. A VU or digital loudness meter looks much more as things sound in terms of level. If you learn how the meter relates to loudness it'll help you make good judgements in "mastering".

More guidelines in a later post...

DIY Mastering Part 1: Loudness Wars

Probably the hottest topic in mastering in recent years is loudness, and certainly one of the most important jobs for a mastering engineer is to achieve a satisfying, consistent level between all the tracks on an album. However the arrival of digital signal processors during the 90s, coupled with the perception that "louder is better" has led to the infamous "loudness wars" - a gradual increase in the loudness of albums over the years, to the point where some are hugely distorted and very fatiguing to listen to.

If you come to SRT wanting your CD loud, we'll be happy to oblige, but my own personal motto is "Louder is better, but Too Loud is worse" - meaning I believe there is a "sweet spot" for every recording where it's loud enough to "work" given the limitations of the original mix, but is not so loud that it suffers. Push something too far beyond this sweet spot and the effects are only negative.

Why is Too Loud bad ? Apart from problems like distortion, pumping or dynamic inversion, a great way to answer that question is to point you here:

www.turnmeup.org

Just check out the video for a great, simple demonstration of why louder is not necessarily better, plus a great selection of "loudness war" links at the bottom of the page.

In a later post I'll discuss how loud is "just right", and the best way to achieve it, but there's other ground to cover before then.