Remember, It's Not Art, It's Noise

In my opinion this should be required reading for all engineers and rock musicians. We are making rock music too perfect with one technology, and destroying it sonically with another.

http://www.npr.org/blogs/monitormix/2009/11/the_death_of_mistakes_means_th.html

Mixing in Preparation for Mastering - Part 2 - Levels

One of the biggest mistakes that mixing engineers make who have not dealt with a mastering room before is endeavoring to make their mixes as loud as an off-the-shelf CD. This is totally counterproductive. The final loudness of the CD is one of the issues addressed by the mastering engineer. Unfortunately many think that making the CD loud is all that mastering is. It is one of the elements of mastering, but certainly not the most important. Your source mixes should be at a relatively low level. Ideally, on a 24 bit mix the hottest peaks should hit somewhere around -6dBfs (dB full scale, meaning 6dB below zero full scale on your digital output meter). This means the average or V.U. level should be around -18 to -20dBfs.

You want to do this for two reasons: First, some of the top golden ears in our industry have determined that almost all workstations and a-to-d converters work and sound best at this 0v.u.=-18dBfs range. Whether you are mixing through an analog mixer or summing amp or in-the-box you will hear a very noticeable improvement in the clarity and space of your overall mix, especially in the vocal range. The vocals seem a lot less stressed and crowded, everything seems to breath better. Probably not coincidentally, this is the 'standard' that Sony and Phillips set for average level when they introduced the PCM digital format that we use today. The problem is it was never enforced as a true standard, so mastering and mix engineers were allowed to make CD masters as hot as they pleased, which has ruined the quality of many potentially landmark recordings since around 1995 which is when the first ridiculously loud CD's began being produced. We'll address the 'loudness wars' in a future blog entry.

The second reason you should not crowd 0dBfs on your mixes is that digital mastering processors need some headroom to work at their best. If a mix is slamming all the way to digital 0, the mastering engineer has to lower its level before he can do any digital processing, which means he's performed a dsp step before any processing has been done, and the signal quality has been slightly degraded.

The upshot of this is you should not apply any eq, compression or limiting across the stereo buss as you mix if it is for the purpose of making the mix louder.

If you mix at lower levels and without stereo buss processing as described above, the mastering engineer has his/her complete palette of tools to choose from. If the mix has not been compressed or eq'd he can choose digital, solid state analog, tube analog or any combination of processors to get the best sound possible.

Caveat: If you are using a buss compressor to get a particular compressed sound, as is often heard in heavy metal, or a rhythmic pumping you might hear in some electro-pop or dance music, and you can't get the flavor of mix you want without it, then by all means use it. But again it should be to add a particular color to the mix, not to make it loud. If you are unsure, print one mix without buss processing and another with so the mastering engineer can choose which works best for the end result.

Most problems with dynamics will usually come from drums and percussion. If you have problems with your drum tracks being too dynamic, don't compress the entire mix, assign the drums to their own subgroup and add a compressor/limiter across that group alone. This would apply to any group of instruments/vocals that you are having trouble getting to sit properly in the mix.

TWO METHODS FOR ACHIEVING -18DBFS AVERAGE LEVELS

If you are mixing through an analog console or summing amp, route a 1khz tone to the stereo output and adjust its gain so your master output V.U. meter reads 0. Then adjust the input sensitivity of the A-to-D converter that you are mixing to so its digital peak meter reads -18dBfs. Now if you mix so your output V.U. hovers around 0, you'll be hitting the digital recorder at that ideal -18dBfs average level. Some engineers prefer lower average levels of -20dBfs and even as low as -24dBfs. Experiment and listen to mixes at these different levels to learn where your A-to-D converter sounds best.

Here's a million dollar tip if you are recording and mixing in-the-box: The trick in all-digital recording and mixing is to learn to record your individual tracks at a lower level, so that during the mix you can have your channel faders close to unity gain (no boost or cut) and your master fader at unity gain, and the resultant mix be hitting that ideal 0v.u.=-18dBfs to -20dBfs range, which should put your peaks around -6dBfs. Here's the deal; the more you are boosting or cutting the level of a channel during a mix, the more dsp you are performing and the more digital artifacts you are creating. Many engineers have learned the technique of setting their monitor faders at unity gain, and then recording the individual tracks so they are getting close to an ideal mix without having to move any monitor faders up or down, and again where the average level of the monitor mix is hovering around -18dBfs. Then during the mixdown they most often have to adjust the channel faders no more than a dB or so to fine tune the mix. This takes a lot of practice to get right, as you will eventually be recording your tracks at a lower level than you are used to, but the result is a mix that has a depth and clarity to it that you've probably not achieved before.

MAJOR CAVEAT: The above only applies if you are tracking at 24 bit resolution. By employing this technique some of your tracks may be recorded at a very low level. The digital noise floor of a 24 bit recording is so far down that this isn't an issue, but a 16 bit recording is a different matter, and if you record low level tracks at 16 bit you will probably have a hashy mess when you mix. If you are tracking at 16 bits you should endeavor to record each track within 2 or 3dB of 0 full scale.

You should not worry about the perceived volumes of your songs being different. Again one of the jobs of the mastering engineer is to match the perceived levels as well as eq so there is a consistency to the tracks in both volume and tonal balance.

Many engineers have already learned that mixing at the proper levels for mastering can potentially cause a problem: If they give their clients a reference CD of the mixes that is half the volume of an off-the-shelf CD or lower, then the client will likely freak out. So now it is common practice for many engineers to do proper 24 bit high resolution, low level mixes to be delivered for mastering, and then add a limiter across the stereo buss, crank up the level and run the mixes again for making the client's reference disc.

Mixing in Preparation for Mastering - Part 1: Audio File Formats, Sample Rates & Bit Depths

In order for your mastered tracks to have that sparkle and clarity that you envision, it is important to follow some mixing guidelines. For these discussions we'll assume the project is for CD-Audio, but all the basics apply no matter what the final delivery medium.

First we'll address digital audio file formats, sample rates and bit depths.

1.) DO NOT SAMPLE RATE CONVERT. If you are mixing 'in the box' or through an external digital mixer, the mix files should be at the same sampling rate as the session. That means NO SAMPLE RATE CONVERSION. Hopefully you tracked at 48k or ideally 88.2k or 96k, but many engineers make what seems a logical assumption that since CD-Audio has to be 44.1k, then they should convert their mixes to 44.1k even though the session was tracked at a higher sample rate. There are three reasons not to do this. First, for ultimate sound quality the project should be mastered at the higher sample rate at 24 bits and then downconverted to 44.1/16 as the final step before the Production Master CD or DDPi is cut. Second, it is likely that a real mastering room has a much better sample rate converter than those found in even large studios. And third, there is a growing trend of artists and sites offering hi-resolution downloads, so it is advisable to have the mastering room create a separate data master containing the mastered 24 bit files at the higher sample rate.

2). MIX AT 24 BIT RESOLUTION. Even though your session may have been tracked at 16 bit, it is important to mix at 24 bit resolution. The reason is that if you do anything more than play one sound file at unity gain out of one buss, even something as simple as changing the gain by 1/10th of a dB, your system has to expand to a 24 bit word length internally. So if you output your mix as a 16 bit file, you will create truncation distortion and lose fidelity. Since hard drives are so inexpensive these days, you really should be tracking as well as mixing at 24 bit resolution.

In the mastering world we are seeing a disturbing trend of people wanting to deliver mp3's as sources. mp3 is barely acceptable as a consumer audio format, and is certainly not suitable for mastering.

CAVEAT: Know Your System! If your DAW or digital mixer operates at 32 bit or 32 bit floating, you need to apply 24 bit dither if you are outputting 24 bit mix files. Or you should output them as 32 bit files and inform the mastering room of this.

Relating to points 1 & 2, There is no 'getting back' quality. If you have created 16 bit mixes, loading them into a program that will output them as 24 bit files will do nothing for you. All it will do is add 0's to the lower eight bits. The sound quality will be the same but the file will just take up more disk space. Likewise upsampling a 44.1k file to a higher sample rate will often decrease quality except in the best of sample rate converters, and then the quality will likely be the same, it will again just take up more disk space. If all you have are mp3's of your mixes, converting them to .aif or .wav will not improve their quality. In fact, you will lose quality with such 'transcoding'. If all you have are mp3's any qualified mastering engineer will know how to handle them to result in the best quality possible. The same is true if all you have is an audio CD-R for a master - it's not doom, many great records have been made from 44.1/16 masters.

3) AUDIO FILE FORMATS. All mastering rooms should accept any of the standard file formats - .aif, .wav, .bwf or .sd2. Normally interleaved stereo files are preferred at the mastering room, but split L/R is fine and there is no difference in fidelity. Also, keep your file names under 15 characters. It's not necessary to name the file with the full song title. Just the first two or three words of the title is fine. See the documentation topic below.

4.) DELIVERY MEDIUM. Most mastering rooms should offer you the option of uploading your mixes. You should put all of your mix files into one folder and then zip that folder prior to uploading. Zipping a folder will perform and internal checksum which ensures that nothing was corrupted during the upload/download. If you want to deliver your mixes on disc, make sure you are creating either a data CD-R or DVD, not an audio CD-R. If you have tracked and mixed at 48k or above at 24 bits, and then you put your files onto an audio CD-R, you have lost fidelity. The reason is that an audio CD-R, like CD-Audio, can only be 44.1k/16 bit, so even though you may not realize it your CD burning software has converted your files to 44.1k and then dropped the lower 8 bits, and you have lost fidelity through both an inferior sample rate conversion and the file has been truncated. On a data CD-R or DVD, the audio files can be of any sample rate and any bit depth. Plus the method in which a data disc is written is much more accurate than an audio CD-R, so there are no errors on the data disc. Your 24 bit higher-sample rate files are much larger than CD-Audio files, so an album's worth will fit on one DVD-R, but will require 2 or more CD-R's, which is fine.

Any mastering room should also accept your sources on a Firewire or USB drive.

5.) MULTIPLE SAMPLE RATES. Do not mix sample rates unless clearly noted. Mixed sample rates often occur when multiple studios and/or engineers have been involved in a project. One engineer may have tracked and mixed at 48k, another at 88.2k etc. If you have a situation where your mixes are at different sample rates, put them into separate folders indicating the sample rate of the files they contain. Bit depth does not matter, if some of your mixes are 16 bit and some 24 bit but all are at the same sample rate this will not cause a problem at the mastering stage.

6.) EDITING AND OTHER PROCESSING. It is important that you deliver the first generation mix files for mastering when possible. They should not be loaded into any program to convert .aif to .wav, or split L/R to interleaved or any other seemingly transparent process. They ESPECIALLY should not be loaded into any workstation for normalizing, fades, edits etc. Your mastering engineer can easily perform fades and edits, and normalizing should not be done in any case. In most cases eq, compression or limiting should not be applied across the stereo buss while mixing. We'll address that in the next post.

CAVEAT: If your project will require a lot of editing, sometimes budget will not allow editing in the mastering room. If you do your editing in the studio, just be sure that everything stays 24 bit, the sample rate stays the same and that no level changes are done if at all possible. If your editing requires a section of a song to be raised or lowered in volume, then 24 bit dither should be applied when the finished edit is output.

7.) DOCUMENT, DOCUMENT, DOCUMENT. Too much information is a good thing. Your sources should be delivered with documentation indicating the sample rate and bit depth of the files as well as the title of the file and the corresponding full title of the song. It is also helpful if your mix engineer can provide details of whether the mix was done in the digital domain or through an analog mixer, if analog tape was used at any stage and whether stereo buss processing was applied and if so what kind and how much was applied and if any dither has been applied at any stage.

8.) ONLINE DELIVERY. If you are going to make your finished project available through download only, do not assume that you can lower the quality of any steps in your production. Please read our first blog entry Audio Production in the Age of mp3 and AAC for details.

Don't Forget the Future - Archive Your Music

3/24/11 - Some very important news you need to read concerning archiving. After you read this post, please go to Alarming News.

When an artist/producer finishes a project, they are often so beaten down by it that they don't think of ordering at least a production master for their own archive. (Archiving means to store important information for a long period of time.) And by the time they realize this it may be too late to obtain one. Many CD plants will not return the Production Master CD (PMCD) or DDPi that you send them. That way you are locked into using them for additional runs. Glass masters are not archived at CD plants as many tend to think. A CD plant will only have a certain number of glass discs that are then re-used over and over again. If you order a new run of CDs they will cut glass again from your master that they have on file. Or in some cases the plant creates an image file of your PMCD, or copies your DDPi to their drives, and then destroys the actual disc. And what many have learned the hard way, most of the ads you see for CD manufacturing are not CD plants, but brokers acting as a go-between that normally use several different plants. So as those people go out of business, there is often no record of what CD plant was actually used for a given project, so the master is lost.

But producers, artists and labels should consider not only having an additional PMCD or DDPi of their own, but a data backup of the mastered project in high resolution as well. Here is how it works in the mastering process (if you are dealing with a real mastering room):

Ideally your original source mixes were at 24 bit resolution, and mixed at the same sample rate at which the session was tracked. And hopefully it was tracked at 88.2 or 96khz. Regardless, the mix engineer should not have sample-rate converted the mixes. We know that CD-Audio can only be 44.1khz, 16 bit resolution. But the mastering should be done at the higher sample rate of the sources and at 24 bit resolution, then downconverting to 44.1/16 should be the final step before the PMCD or DDPi is cut. Even in the worst case where the source mixes were delivered at 44.1/16, the mastering will still be done at the 24 bit level. So you can still get mastered files at 44.1k/24 bit, which will have a sound superior to the CD.

So why would you want these high resolution files? We can look at two possible scenarios:

First, if we follow the current trend where the majority of audio will be delivered online, and if things stay at the relatively lo-fi of our current mp3 and AAC formats, then you will have the best sounding masters possible to create new bit-reduced files as you need or as technology changes. As I explained in my first post, your master has to be of the utmost quality if the bit-reduced versions are going to sound decent. So if you have mastered files at a higher resolution than even CD-Audio, then any down-converted files you create from them are all the better.

Second, and more importantly, we are now seeing what industry insiders have predicted (hoped for) for a couple of years - that as internet speeds increase, and as storage gets smaller and cheaper, we will see high-resolution download options for consumers interested in better sound quality. You now see many bands offering at least CD resolution WAV files and even better on their personal sites as a more expensive option to the mp3 download. Radiohead's "King of Limbs" was offered as 44.1/16 WAVs for instance. And we are beginning to see sights like hdtracks.com that offer current and classic albums in as high as 176.2k/24 bit! So as this trend hopefully continues you will eventually (or even now) be able to offer high-resolution downloads of your music.

1/18/12 - Click Here for important update on tracking and mixing in HD.

Less likely, if a new high-resolution consumer audio format is released that is actually accepted by the general public, then you have high-resolution mastered files that you can release on the new format. Unfortunately, DVD-Audio and SACD were miserable failures. And the majors aren't likely to get behind any new hard delivery mediums anytime soon, if ever. 

A qualified mastering room will be able to offer a DVD containing your high-resolution mastered tracks as well as a Production Master DDPi file set for CD manufacturing, and your unmastered source mixes. At DES Mastering it is our standard practice to also include text files of the pq and delivery logs, metadata verification as well as mastering details. Ideally you would get both a Production Master CD and a data DVD as described for your archive. As this will probably run a few hundred dollars, you should be able to arrange with your mastering room to have all of this created at a later date. Mastering rooms can usually create archival masters within a two or three month period after the project is finished.

IF YOU HAVE DAT MASTERS, YOU NEED TO GET THEM TRANSFERRED NOW!!!

If you have important music on DATs you need to get them transferred to standard audio files as soon as you can. There are two reasons for this; number one is that the DAT is a mechanical format that is subject to failure. Even in mastering rooms with well maintained machines a snag can happen and a tape can be ruined. Also, depending on how the tape was stored, the data can become unreadable.

One of the biggest reasons however is that DAT machines are no longer made, and are no longer commonly seen in most studios. And fewer and fewer technicians can repair them or have access to parts. So before they all go away, get your DATs transferred!

Audio Production in the Age of mp3 and AAC

A lot of people are suddenly questioning whether their recording and production quality standards can be lowered if they are strictly using online delivery, and the music is going to be reduced to the quality of mp3 and AAC anyway.

Here is the surprising truth: The quality of your production chain is MORE important if any of the data-compressed formats are going to be the primary delivery medium. AAC for iTunes or mp3, even at the highest kbps rate, are not near the quality of CD audio. When your music is converted to these formats, it will lose quality. So the better the quality of your final mastered project, the better the data-compressed files will sound. That may seem like a very obvious statement to some, but surprisingly a lot of people see it backwards; the delivery medium is of relatively low quality, so the quality of the original recording is less important. They couldn't be more wrong. In this age of internet delivery, from tracking to mixing to mastering you need to pay more attention to quality than ever before.