Master bus processing is a key aspect of a mix and, if done properly, can give your tracks a more finished sound. Most people readily understand the overall concept of mixing, but not so many pay attention to what is happening on the master bus. This month, I''ll discuss some of the important things to keep in mind when dealing with the master bus and share the processing chain that I use.
The master bus is the main stereo sum, or output of any mix. It is the last and final signal-flow point before your track gets printed to a final stereo mix. Whether you are working in the box or out, it is critical to know exactly what is happening on the stereo bus. You should be aware of such factors as the overall dynamic range and the frequency spectrum of your track when dialing in your finished mix.
PEAK VS. RMS
It''s key to understand some principles regarding the overall dynamic range (i.e., the overall loudness) of your mix. In audio engineering, there are two types of loudness: peak and RMS. Peak represents the absolute loudest signals that are present. RMS is the average loudness of all the signals present. While it is important to know exactly both the peak and RMS levels of a mix, the RMS offers more insight as to how loud a mix will be perceived by the listener. Humans perceive loudness based on RMS because our ears and brains can''t respond to every single frequency and sound in a complex waveform. It is also important to know what the overall peak level is to avoid clipping and distortion on your mix, especially when working completely in the box.
There is much debate about the dynamic range of today''s popular music. Many believe a more natural sound with a wide dynamic range is best, while others try to smash the dynamics down so hard that the end result is an ultraloud, solid block of a waveform. I believe both have a place in modern music. However, most of the commercial projects and remixes that I work on end up being pretty loud. The main reason is that in the clubs, a track needs to hit as hard as possible. As a result, most club mixes are compressed pretty heavily.
I don''t really consider master bus processing to be the same as mastering. Mastering is a separate process that not only deals with what is happening on a single track, but what is happening on a group of tracks, like an album or EP, to ensure that they all have consistency as a finished product. Still, not all projects I work on will immediately get mastered by a separate mastering engineer, so I always pay a lot of attention to master bus processing to make sure the mix leaves my studio sounding the way I want it to.
It''s never too early in a project to start paying attention to the master bus. As you go along, it''s critical that you always leave some headroom, level-wise, for your master bus processing. Otherwise, you''ll start turning everything up as you add other elements and you''ll start clipping the master. This is one reason why I wait as long as possible to add the final automation to my mixes. I want to be sure that I can turn things down and adjust levels so as not to hit the master bus too hard before the final processing chain.
FIG. 1: Di Pasquale''s master bus processors typically comprise Logic''s Channel EQ and two Waves plug-ins: the SSL G-Master Buss Compressor and L3 Ultramaximizer (limiter).
I typically start making initial adjustments to the master bus chain (see Fig. 1) as I''m putting the track together, especially on remixes or productions that are done entirely inside the box. I''ll instantiate the plug-ins and get some rough settings going early on. This prevents spending tons of time mixing things to sound a certain way only to discover that the sound changes significantly after the master bus inserts are added.
Once I have the final where I want it, I turn my attention to the master bus. I loop the loudest section of the song and work on that first. This may be a chorus coming out of the BREAK or whatever section has the most energy. After I get the EQ, compression, and limiting set, I can listen to the whole song to make sure the levels are where I want them. In some cases, I will automate the master bus effects to keep a consistent sound throughout the whole mix.
FIG. 2: It''s useful to have two multimeter plug-ins active: one at the beginning of the chain and one at the end.
The first insert in my master chain is a multimeter, which lets me check frequency and level (see Fig. 2). I either use Apple Logic''s built-in multimeter or one from Waves or iZotope. This meter shows me the overall dynamic range of my mix as it hits the master. I study the frequency spectrum to see what the high end and low end of my mix are doing, and I make sure that the levels are not clipping. Set your meter to show both peak and RMS levels. (I also put a multimeter at the end of my master chain, which lets me check the dynamic range post-processing.)
Next, I insert an EQ and typically focus on EQ''ing three areas: First is the high end. I will always add a little high-end shelving to accentuate the overall brightness to the mix. Ultimately, the boost will start somewhere between 6 and 10 kHz, depending on what I hear in the mix. The next area I listen to is the 300 to 400Hz range. This is where a lot of muddiness can creep in. If it''s muddy, I''ll put in a sharp parametric cut to help reduce it. Finally, I listen to the low end. I like to add some subtle low-shelving EQ to help glue together the drums and bass.
The next insert is a stereo compressor, with which I aim for about 4 to 6 dB of gain reduction. If I use the Logic compressor, I will start with the “analog tape” preset, which really sounds good across the whole mix. Next up I might add a multiband compressor. I don''t always use one, but it is really great when I want some extra punch in the low end. The last insert is a limiter, which applies the finishing touch to the mix. It''s where the power of the mix comes out. My go-to plug here is usually the Waves Ultramaximizer, but sometimes I''ll use Logic''s Adaptive Limiter. Either way, I''ll typically set the output ceiling to -0.1 and then adjust the threshold to get around 3 to 4 dB of attenuation.
OVER AND OUT
In the end, the main goal of my master bus processing is to make sure the frequency spectrum sounds balanced and looks that way on the post-processing multimeter. As for the overall dynamic range, I shoot for somewhere between -10 and -5 dbfs during the loudest sections of the song.
Once everything is sounding the way I want, I will bounce a pass and re-import it to listen to it and look at the waveform. If I know the project will be professionally mastered, I''ll bypass the limiter and typically just use EQ and stereo compression. In these cases, I will just make sure the mix sounds exactly the way I want, with a little bit of headroom left for the mastering engineer. Like with everything in music production, the best method is to do what sounds good to you, and take time to experiment and get the results you want.
Vincent di Pasquale is producer/remixer who works out of his project studio. He has remixed songs for Madonna, Nelly Furtado, Mariah Carey, and many others; and is the author of The Art of the Remix, a comprehensive interactive remixing course available at faderpro.com.