Subsequent Mastering

Thursday, 18 June 2015

Multiband Compression : let's talk about it calmly...

"Argh! get off my master! you've split the bands... you ruined my beautiful mix, multiband heathen!"

"The mix was finished but we couldn't get that damn low C note to work, after hours of processing individual channels we stuck a compressor over that frequency range and tucked it right back in, it sounds so TIGHT now!"

Hang on a minute... what's going on? Read any mastering forum and see people slamming their heads against the keyboards at the mention of multiband compression in the context of mastering. Why the hate? what even is it? and why is it so awful?

Multiband compression is a style of audio processing where the frequency spectrum is split up using a crossover (much like a PA or speaker system), processed, and then re summed back into one signal. In a true multiband system each signal created by applying a crossover has individual parameter control, which a single separate processor available for each band.

A fine visual example of crossover
( FREE crossover plugin by RS Met)

The technical theory of splitting bands, applying dynamic control and summing back together comes loosely from broadcast technology, where you have a lot of audio and a narrow everything (bandwidth, dynamic range) due to the nature of radio broadcasting and a large range of playback scenarios to consider. A famous type of multiband compressor all types of audio engineers use is a "de-esser". This is a multiband compressor with only one band active to edit (often the highest band or a mid band focused on the S area of the human voice, or both). This technology is also replicated in vinyl cutting, often known as a "high frequency limiter", but essentially the same thing tuned for a specific task.

So hang on, multiband compressors are on almost everything already? so why is there mention to quite a lot of audio engineers a cue to exhale a huge passive aggressive sigh?

Well this is what I'm hoping to debunk and offer some closure on. First of all, let's take a short modern history lesson..

The advent of the compact disc in the 1980s  pushed for the development of digital mastering (and general audio processor) technologies. One of the first true pro audio devices taken up by audio engineers was the TC Electonic M5000 digital mainframe ( This device was a host for several different algorithms, notably it's NON LIN reverb/delay and it's MD2 mastering software. Although clunky and limited by today's standards this is still a HELL of an audio processor. It's fixed at 44.1kHz and has a complex array of pages and layers to get to what you want, but if you want to control one to three frequency areas dynamically it's still up there with the best! trust me, until it blew up, I was using my studio partner's old M5000 (which sat in the rank infront of me for months until I even bothered to patch it in..) on many of my most successfully bits of work!

Man I miss this thing! The big black mastering brick...

It worked great, it's a real pro tool with the kind of design which for audio engineers makes sense and to anyone else is pointlessly baffling. 

So what happened, this sounds great right? serious tool for serious bits of work. Well... TC took this technology in two directions: the M6000 (later known as System6000, now a standard in many pro audio suites) and the Finalizer series. The latter is possibly to blame for the misunderstanding of multiband compression, or at least its marketing.

A powerful tool is damaging in the wrong hands..

Big leaps forward in the programming of digital audio equipment had happened between the MD2 development and the Finalizer hitting the market, and this allowed for... presets..

Earlier I mentioned broadcast processing and multiband, this kind of fixed processing with all the bands engaged was totally the done thing in broadcast by now, but the current multiband mastering processors from TC and also other great companies such as Weiss (see previous article on their original digital mastering processor!) forced you to engage each band on request and set up from scratch. The Finalizer, and it's competitors such as the DBX Quantum and Drawmer Masterflow allowed you to load settings with processing applied as default. It's worth stopping at this point before I accidentally drag these units through the dirt to point out that all these units are pro standard audio processors, I would happily work with any of them, and before you think I hate the Finalizer, I have an OG 44.1kHz Finalizer which I bought to use as a second layer of that good old predictable TC multiband on really tricky/restoration jobs.

DBX Quantum: A fiddly thing, but with some features not found in it's competitors

Drawmer Masterflow: Slightly obscure now, but you'll find a handful of MEs singing their praises online still

The issue here is how the user was convinced to use these specific units. The concept of presets/wizards/whatever is something which I can't honestly say has done anything other than damage probably quite decent sounding recordings or trick people into hearing something they're not. Aha, so now we are back to the beginning again, the whole "trashed recordings" thing, but before we smash our heads into our keyboards let's have a think about this.

What sounds "bad" about a really well designed crossover, with top end compression with musically selected parameters and values on each resulting band? well, nothing! So why do we hear so many depressing screwed up, phase mis-aligned, smeary, pumpy messes? Because the button was there to press, and often placed at the start of manual and in big inviting print on the unit itself.... In the late 90s there was an arms race to sell "home mastering" gear to the sudden "project studio boom" (a revolution for the good for independent music!) and everything went a bit whacky. The resulting generation of pure confusion about multiband compression can be pointed towards this in my opinion. The shame is when people get multiband processing and ALL THE BANDS IN MOVING ALL THE TIME, which unfortunately is what a hell of a lot of those presets do.

The native plugin revolution in audio created a LOT, and I mean a lot of Finalizer clones, the most popular being Izotope Ozone, a plugin which when mentioned is like actors speaking openly of "the Scottish Play".. but again, although this thing has some bizarre features such as mastering reverb(?!) it's a pro level processor, it suffers from its marketing and pressure to make something crazy and colourful. It's also worth mentioning that Izotope are no fools, their RX restoration software is only rivalled by the bafflingly expensive Cedar systems!

(Amendment #1 : as pointed out by two folks, the latest Ozone, as pictured, does away with the Mastering Reverb, good work!)

The dreaded Ozone! 

To summarise: multiband was great, then confused, now great again. The truth is it never went away, and pro mastering engineers, the guys churning out the records we all enjoy never stopped using them, they just kinda had to go quiet for a bit...


  1. Ozone 6 which you have pictured here does not have an option for reverb processing. Reverb was only available up to Ozone 5.