Polaris Studios | The Process
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What is Audio Mastering?

Mastering is the final stage of the creative process of any audio-recorded work.  It is a critical step for musical and audio material in its way to become a finished product, meant to be replicated or listened by consumers.

01 - Ingeniero de Mastering


Process the entire audio content from individual songs to the highest possible quality and to a high overall volume level, compatible with commercial music releases:

The final product from the mixing stage of audio material (let’s call it program from now on) should count on satisfactory features in the so-called “six dimensions of mixing” (balance, panorama, frequency range, dimension, dynamics and direction).   Such material is ideal to be taken to the first step of the mastering job:  The Audio Signal Processing.

There are three core elements necessary to complete the audio processing stage during the mastering process:


The Mastering Engineer

First of all, an experienced Mastering Engineer:  Before talking about technology, processing or exporting formats, you need the know that the person in charge of the process, the Mastering Engineer, is the real key to achieve the desired results.  A Mastering Engineer is a specialized professional with extensive and reliable experience in listening, processing and adjusting audio material to meet the standards of a commercial-grade releases.  This experience can be achieved only by years of technically-oriented music listening, skillful use of audio mastering technology, clear musical references in the sound realm and the capacity of taking right decisions during the buildup of what will be the final result of your artistic effort.   The Mastering Engineer is, without a doubt, the most valuable element of the process.

Top-quality Mastering Technology resources

Mastering Engineers / Studios rely on a series of specialized technology elements (both hardware and software) to perform the mastering tasks.  The gear found in serious modern mastering studios is always a combination of the best sounding, most precise and best calibrated signal path elements available in the industry, which need to be properly driven by the Mastering Engineer to achieve the goals of mastering.  All the processing tasks mentioned above (Level Raising, Equalization, Compression, Limiting, De-Essing, etc.) are performed on a professional Digital Audio Workstation (DAW), a specialized mastering console and dedicated outboard gear, carefully selected and driven by the engineer.

Monitors and Acoustic Environment

Professional mastering facilities rely on a specific monitor selection, chosen to provide a flat and wide frequency response, with as low resonance tails as possible. The largest possible width on frequency response is essential in the bottom end of the spectrum (low frequencies), which means that a large-monitor setup is often needed, sometimes including an additional subwoofer speaker. So, most commonly used monitors for recording and mixing, especially near-field speakers, will not provide the required response for mastering works.  Any mastering facility will count with at least 2 or 3 pairs of monitors, which will allow a precise manipulation of frequencies and multiple checking of the playback sound of the mastered material in different sound systems.

Regarding the mastering room, we can shortly describe it as an ultra-quiet environment, mostly built as a freestanding structural frame inside another frame (“a room inside another room”).  This provides buffers of air, space and mass that are useful to getting rid of any external noise entering to the studio. Also, the placement of wall absorption materials needs to be designed specifically for mastering purposes and calculated with base on the room shape and dimensions, features of the mastering monitors and some specific capabilities of the mounted outboard gear.

If the musical project includes several themes:

After processing the audio material from each song from an album, the next step is to adjust the overall level, dynamics, EQ and effect processing of the sequence of songs to form a cohesive unit, sonically-wise;  this goal is achieved by means of a sequential transmission of the entire audio program content through a series of signal processors designed, calibrated and driven for these purposes, all of this under careful listening by the Mastering Engineer.

Foto Principal 2
Assign an order to the sequence of songs

The next stage of the process is to assign an order to the sequence of songs contained in the program; as you can guess, this order is commonly proposed by the artist but sometimes can benefit from some advice from the Mastering Engineer; the order of songs in an album is an important element for the listener to consider it as a whole, and the Mastering Engineer has a wide experience and great perspective in this regard, also having some advantage because of the fresh ears and his “outsider objectivity” regarding your project.

Once the songs are arranged in the desired order and sounding as a whole entity...

…following is the program assembly; this is, the edition of each song’s start and end, spacing between songs, designing the fade-ins and fade-outs for each song and satisfying any special requirement from the artist regarding the transitions between the different tracks.   After this, the Mastering Engineer will finally appreciate the entire material as a single unit, which allows to make any further adjustment to the previously-made audio processing, in order to provide a “sonic direction” for your entire work.  This is a crucial element of any finished project and makes an important part of every great album in music history.

Before starting the mastering job over your material

We will ask you to answer you a short “subjective questionnary” to know a little about your expectations regarding some of these elements; we also would want to know about any albums that you would identify as sonic references, so we can have a better idea of what you’re after and fulfill or even surpass your requirements.

03 - Metadata

Assignment of all the required metadata:

It is important not only to check the audio data contained in a master but also the metadata. The term metadata refers to any data on the disc not related to audio content. It may be markers that indicate beginnings and endings of the tracks (called “PQ bits”). It may be ISRC codes , which are embedded in the data stream and indicate content origination and ownership. It also may be data such as copy protection flags, emphasis status bits, or any information that affects the behavior of the playback device. The simplest form of quality control over a finished master is to simply put the CD into a player, jump to the beginning of each track and make sure that the markers are positioned correctly, then rewinding and checking where the markers exist on the CD, to be sure that these also are properly located. While it may seem obvious, it’s always worth confirming that this information was adequately written by the mastering software onto the CD master, before sending it out for replication.

Final Quality Control of the audio material:

The Quality Check (QC) of an audio program involves checking the master for technical flaws, rather than aesthetics.  Here are the things that we do when performing the Quality Control of a disc:

The first thing to do is to listen back to the entire program to make sure that any random noises were not introduced during the mastering process.  If there are newly-detected noises from the recording stage of the production, these will be logged to a cue sheet and notified to the artist (many of these noises will become apparent during the audio processing of the material and noticed for the first time by the Mastering Engineer).

During the QC phase, we will also check the placement of the start and end IDs on a disc, to make sure that the track markers are located where they ought to be; it’s also necessary to be sure that the beginnings and ends of the songs are not cut off.  Then, it’s time to check the text information in the master, which is part of the metadata.

03 - Monitors and Acoustic Environment
06 - Temas de referencia

Issuing of the finished Master in the desired delivery format

We have the following delivery formats :

For individual tracks : We can process your issues and deliver your master completed under the formats you want. We can also add any metadata that you require for your material if necessary.

For full-length albums or Eps: Currently , there are 2 main formats of delivery of completed masters: The Audio CD or DDP file .



available Uncompressed / HQ Compressed formats:

.m4a (AAC – see the “Mastered for iTunes” section)

.wav (WAVE)

.aiff (AIFF)

Apple Lossless

Compressed files (.mp3)...

…are also available; they will be sent to you separated from the main DDP file (or along with your uncompressed mastered file if your work consists in individual tracks).  Our MP3 files are generated from Sonnox® Fraunhofer™  Pro-Codec software to keep the best audio quality possible in your compressed file.



DDP Master

Issuing of finished mastering works is currently made in this previously mentioned new standard, the DDP (Disc Description Protocol), due to a number of reasons:

DDP has far fewer errors than any other master medium, thanks to computer-performed data error correction. CD-Rs and PMCDs (a master CD format used in the past years) have a less robust error correction, and will output data whether it is good or not. So, it is possible to get different data each time you play the disc, which requires an extremely diligent replicator to get an error-free transfer from a CD-R. Also, audio CDs don’t protect data from errors, since they assume that the CD player will hide or conceal any errors during playback. This situation leads to errors in replication when recordable CDs are used as physical mastering media.

With DDP, it’s easy and safe to go over the 74-minute limit associated to CD-Rs. Some CD brands offer that possibility for daily use purposes, but as you can guess, it’s not a good choice to rely on this for putting your master on that kind of media.

DDPs are simply safer. It’s impossible to play back a DDP file without the right equipment or software, which isn’t available for everyone. This means there is less chance for accidental playback of the master, which may damage the physical medium. A CD-R can get smudged and scratched, but the DDP will stand in its special case (or in a secure FTP server ) until it gets to the replication plant or physical archiving place.

A DDP file, unlike CD-R masters, can only be generated from a DAW featuring professional mastering capabilities.

Audio CDs

While audio CDs have been widely used for master issuing purposes over the last 20 years, they are currently not considered the best choice in comparison with the modern delivery format, the DDP master.  During a CD recording process, no matter how good the media and the burner are, there will always be a number of errors in the data simply as a byproduct of burning the disc.  Disc Description Protocol (DDP) files, however, are delivered as data on a CD-ROM, DVD-ROM or FTP (File Transmission Protocol), and are the current industry-standard method for audio delivery files for replication.  The error correction used for DDP is designed to be more robust than that of a CD and ensures that the audio master received by the replicator will have as few errors as possible in its contained data.