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Christopher A. Dion, B.Eng., M.A.Sc. is a Mastering Engineer as well as the founder and owner of Quantum-Music Mastering. He is known of his keen ears, work ethics and entrepreneurial talent. He has written many scientific articles and also has 2 patents under his name. Chris lives in Montreal, Qc, Canada with his wife and his young daughter.

Compression: What about room acoustics ?


Last post discussed a bit about how monitoring was important in order to properly hear attack and release time on compressors.

Fred’s question regarding that matter was: What about room acoustics, does it also have an effect on how we perceive attack and release time.

The short answer is yes.

… But a more complete answer follows:

Our perception of release time

Room acoustics affect our perception of release time a LOT. Let’s say you have a long but not wide room with parallel walls, your room will have a long decay of reverb, which will make you think that every hit lasts forever. The effect of the release time will be blurred into the reverb of your room.

Interesting fact #1: I’ve noticed over the years that people tend to use release time settings that are way too slow. Acoustics might be a cause. Slow release time decreases the perceived loudness and attenuates the feel of definition.

Our perception of attack time

For the attack settings, if your room is big enough it won’t be a problem, as the delay between the original sound and the early reflections will be long enough to separate them distinctively.

Unfortunately, that’s probably not the case for most of you. If you operate from home, great are the chances that you have a low ceiling and the speakers are close the back and side walls. That is a real problem. In that case, the early reflections will blend with the original signal, making the transient less clear and defined that it should be.

Interesting fact #2: I’ve noticed over the years that people tend to use attack time settings that are way too fast. Here again, acoustics might be a cause. Fast attack times kills the magic and makes everything sound flat and dull.


All this is all nice, but what can we do about it ?

“Acoustic treatment !” would be the obvious answer, right ?  To write a full document on acoustics is out of the scope of this actual post, but I promise I’ll do so in the next week. There are so many aspects to cover on the subject, that one post wouldn’t make it.

That said, in my opinion, Here are some quick guidelines you can follow:

  • Pick the right room first.
  • Your room shall be as big as possible, with a high ceiling.
  • Get your speakers away from the walls. The speakers shouldn’t be too close to any surface. If it’s the case, build some acoustic panels and using a mirror, install them where it will catch the early reflections.
  • Consider building a cloud (acoustic panels that you hang on to the ceiling).
  • Install a bass trap. It won’t do much about early reflections but it will definitely tight your low end.

And that’s it ?

Not really. The acoustics can have an effect on the frequency response as well. You will tell me that this should affect EQing and not compression settings. Error!

That’s for another post though!

Compression in-depth: The beginning

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As far as I can remember, I’ve been a obsessed with compression.

My father was a live sound engineer. I used to hang out where sound professionals were working. I was just a little kid trying pass time. At the time, I wasn’t aware of the chance I had; I had access to plenty of recording materials. I had access to microphones, tape recorders, mixers, etc. I was playing with it, recording stuff I suppose, I can’t seem to remember.

One thing I remember though, is how I liked recording CDs onto tapes. I just liked the punch of the kick snapping into the tape recorder. It sounded richer and punchier. I had no idea why at the time. Indeed, a tape recorder is very good compressor but also a harmonic generator.

Enough spoken about the past and let’s discuss about we are about to cover here. I’m not here to brag or anything, but I have an ear trained for dynamic. I seem to hear dynamic at a much deeper level that anyone I’ve met.

I want to write about compression, first because it’s a passion for me, but secondly because I feel that compression is a highly misunderstood concept. Some people put compressor on stuff only because they are told that’s what professionals do. Even acclaimed professionals admit regularly admit that they still don’t get exactly how compression really works.

I used to buy a lot of magazine about audio, because I wanted to learn the tricks about compression only to find out that the author of the article didn’t know sh*t about using compression. They seem to set compressors kind of randomly. They seem to understand threshold and ratio, ok, but they don’t seem to know what attack and release settings do.

Here is something funny: People that think they are doing mastering by applying multiband compression on a mix and leach the life out of it instantaneously. Yes, you heard me right: The same people that don’t know how to use a compressor properly end up applying multiband compressor on a master bus. Ouch!

Let’s define some basic rules here.

Rule #1: Forget about multiband compressors until you are a genius at single band compression…And even then, keep forgetting them.

Golden Trick #1 : Use side chain filters on single band compressors in order to treat the dynamic specifically to the frequency range where the problem is.

If you want to become a master at… mastering, or even mixing, you will need to work your compressors at a much deeper level than just adding plugins, applying a preset and guess from there. You will actually need to listen to the material and apply the change you have simulated in your mind before hand.

I would say the first step is actually wondering why a compressor is needed on the first place. Most people’s answer is to bring volume… Terrible answer. I personally never worry about volume, although everything I do sounds naturally loud. Applying compression is all about working textures. Controlling and smoothing dynamics while keeping it well alive and vivid.

When I listen to a mix, everything that seems out of control in terms of dynamic will annoy me. It might be the cymbals that seems to have to much freedom, or the hit of a snare that pops out too much. Whatever what frequency range it is, the recipe is about the same. Using a compressor that allows you to sidechain filter the whole thing, you can isolate the problem from the rest and leave the rest untouched. That’s part of the secret to achieve a very effective, yet transparent compression.

Rule #2: Don’t use preset. Actually listen to the music and give it what it needs.

Golden Trick #2 : Attack and release are the ultimate parameters to define punch and make compression transparent.

Most people don’t hear well attack and release settings. I guess, it isn’t obvious to someone who doesn’t know what to listen at. The most common real reason is that people don’t have good monitoring system. An accurate monitoring system shouldn’t simply have a flat frequency response but also a very fast and precise dynamic reproduction. In that case, all speakers below $600 a pair won’t get you close. The reason is that you will be hearing the speaker transient response rather than the actual transients of the mix. How can you set a release rate if your woofer is slower than the transient? Well, you will end up doing the same thing as they are doing in these magazines: Educated guesses at best. If you can’t afford a $4k+ pair of monitor, just get the best headphones you can afford ($400+) and start from there.

To be good at compression, there is no short cut. You need to:

1. Hear the dynamic well. That includes training your ears, but also have an appropriate set of speakers/monitoring.

2. Try a lot of combination and listen to how the dynamic reacts.

I hope this has been useful to you. Please do not hesitate to leave any comment/question down here. I will definitely come back with more precious information on advanced compression techniques!

Finally: here is a bonus gift to close the post:

Platinum Trick #1: Compress everything that seems out of control, but just a little. Stack compressors with very little Gain reduction on each of them when needed. Keep compression as transparent as possible, but control well every peak. Use relatively long attack time (dynamically alive), and super short release time (transparency). This generally gives the punchiest, yet well controlled dynamic you hear on high end loud and punchy records.


Welcome to our Blog !


Original Articles Coming Soon: Monday, July 13th 2015 at noon.

At the pace of 1 post per week, this blog will mainly cover the 3 following topics:

  • Advanced Audio Mastering Techniques
  • How to succeed as a Audio Freelancer
  • DIY speaker design and considerations

Starting Next Week: We will cover the different types of compressions (VCA, OPTO, FET, VARIMU) with one post for each of them. These posts will contain pictures, audio samples, a description of the science behind each technology, the forces and weaknesses of each of them, as well as some recommendation on their usage.

Stay tuned, it’s coming !