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Advanced Audio Compression:
Multiband and Otherwise

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So I went over the basics.

Now let me discuss some advanced audio compression techniques.

Different Folks, Different Strokes

I talked about attack and release.

Different programmers can create various types of attack and release curves.

For example:

  • An attack can start very quickly, and then, taper off.

The same type of action could be applied to the release, but perhaps, in reverse.

This is not an advanced audio compression technique, per se, but explains why I may have more than one compressor on hand. Voxengo’s Polysquasher lets one have some choice over the matter...

Admittedly this can be very subtle at times.

But, again - at times - extremely handy!!

Hardware Emulation

An opto-compressor, so named after the hardware circuitry it emulates, adjusts its release characteristics depending on the amount of reduction, and time of reduction.

This characteristic can be selected in the Waves Renaissance, and Linear Phase Multiband Compressors.

You may have heard of the term 'knee' or 'soft-knee'.

This simply means that dynamic range compression starts at specified amount below the threshold at a much lower ratio. And as the audio level rises towards the threshold, the ratio gradually increases to the amount that's been finally set.

Not The Straight and Narrow - Above The Law

How an individual compressor behaves is referred to as its compressor law.

I've used the terms linear and non-linear: below the threshold the compressor is 'linear'; above, it's 'non-linear'.

Some compressors, especially mastering compressors, become linear again at higher levels.

I can, with a compressor law like this, preserve the loudest parts of a song with its original dynamics untouched, (after I apply the appropriate make-up gain), and bring out the low and mid volume levels of a song, possibly adding some very nice warmth in the process!

Not Standard But My Favorite

Something similar to that can be achieved with parallel compression.

This is where one mixes in a heavily compressed version of a track with the original.

Bob Katz describes the particulars of this approach in his book 'Mastering Audio”.

When it's appropriate, it's one of my absolute favourite mastering tools.

It’s also the starting point for some very advanced audio compression techniques where I might need to repair a mix and recover - for the artist - valuable time and finances to boot.

But I have certainly used this technique to create some very unique sounds that would be incredibly complicated or impossible with hardware....

...If it BENEFITS the song!!!

Not Narrow But Wide

The methods of dynamic range compression I've described fall the under category referred to as wideband compression.

This means that the compression is being to all frequencies when it is in effect.

Better Than One?

Multiband compression divides the compressor action individually to specific frequency regions. It splits the input signal at selected crossover point. It then sums them back at the final output.

Let’s look at a two-band compressor.

It works separately and differently on frequencies - below 100 or 120 Hz, for instance - than on those above that region. I can actually get some control over specific instruments in a mix, namely the bass and kick drum.

With three-band compression I might benefit from settings similar to this scenario:

  • accentuating the bass region;
  • use the mid-band to 'warm' up the frequencies where the vocal fundamentals generally reside;
  • and leave the highest band and frequencies completely untouched.

With the individual make-up gains of each band set properly, I can get a nice warm verse section, with a nice, tight but 'sparkly', chorus.

This is just an example...

The possibilities are almost endless. Like any esoteric procedures...

Advanced Audio Compression Techniques...

...are something that I’ll use only when necessary.

My philosophy is:

  • “...the simplest is the best..."

But when they are needed, they can be almost - dare I say it - life-saving!

Find out what I can do for you right now with a free sample.

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