Audio monitoring

Details
Written by Jon Buer

Audio Monitoring

Monitoring – What’s it all about?

Intro

This is about monitoring as reference system in a home studio. And it is indeed one of the most important parts of a good functioning homestudio. An accurate sound reference system which you are familiar with is a must for a reliable mixing result (and mastrering for that matter). It’s not about a lot of moneyspending, but rather about buying dedicated monitors for homerecording suitable for your room, and well thought placements and environment design. And then it involves a bit of sound, acoustic and technical knowledge.

The monitors are your best friend in:

  • Recording
  • Mixing
  • Mastering
And if you want your recordings, mixes and masterings to be:
  • Clear (not muddy)
  • Well balanced
  • Translate well to Car stereos, Hi-Fi and other sound systems.

It will depend on a well thought out:

Selection

There’s 3 main types of setups when choosing monitors.

  • A pair, setup for stereo monitoring
  • A pair with a SubBass added, for Stereo with added sub reference in more urban genres.
  • A surround setup, from 2:1 and upwards.

You should never buy monitors without test-listening. Listen to several at the dealers shop, select a setup, and take them home to listen to them in the environment they will be used in. Never pay before testing.

Testing means to listen for:

  • Bass – Tight & controlled or Uneven & muddy?
  • Stereofield – Wide & good separation?
  • High end – Smooth & crisp or Harsh and tirering?
  • Detailes – Do I hear all the details that the mix is containing?
  • SubWoofer – Is the low end (Sub-) frequencies coming through and giving the mix a distinct weight?

All these questions can only be answered in the environment where it is going to be used, as the environment will influence what you’ll hear. The monitors placement in the environment will influence the audible result.

Placement

There’s a lot of things to consider when you shall find the best possible place and position for your monitors.

  • The Speakers and you should make up an equilateral triangle so you’re sitting in the so called "Sweet Spot" when you’re mixing.
  • The tweeters shall have the same vertical level as your ears.
  • The speakers should be "facing" you.
  • The speakers shall be standing with tweeters at the top and bass at the bottom.
  • Preferably at least 25 cm from walls.
  • Use stands if you got the room for it.
  • Both speakers shall have equal distance to back walls and side walls. (That means that the mixing desk should be at the centre of the back wall preferably)
  • The distance from side wall have to be different from the distance to the back wall, to avoid interference and canselations.

Use the "Acoustic Space Control" on the monitors if they have any. (internal EQ control related to placement. Especially important in small homestudio environments.

  • Full-space (Space on all sides),
  • Half-space (Against walls or desk),
  • Quarter-space (In corners or shelves).

Finally you should test your monitor placement by listening to a quality commercial CD, and try to move the speakers around to find the widest sweet spot with balanced sound.

And adjust the speaker volume equally. Watch out for differences between the speakers that can occure from differences in the mixer output.

Subwoofer placement 

  1. Allways on the floor.
  2. Preferably in the middle between the left and right speaker.

Testing placements 

  1. This yields for both speakers and subwoofer.
  2. Using a pink noise signal through the speakers
  3. Meassuring with a SPL meter

Room acoustics

Standing waves and phase canselations

Sound follows the physical laws of reflection when it hits a surface, and the more flat, smooth and hard the surfaces are the more problematic the reflections will be to get an accurate monitoring. Parallel walls are a special situation, because the waves are reflected back into the same path that it was coming from, and that are resulting in the so called "standing waves". This is a no-no in room acoutics when it comes to studio monitoring for mixing music. Any such surfaces, be it walls, ceilings, floors, doors and windows, can cause problematic reflections. These standing waves can cause phase canselations and makes it impossible to monitor accurately. Anything that is making the surfaces softer, less flat or less smooth will reducing this problem. Curtains and shelves are such; we could call them Diffusers.

Diffusers – are used to prevent standing waves by reflecting waves in various directions or angels. The more complex the reflections in the room are according to directions and angels the more evenly reverberant character the room will have throughout its space. Through this you’ll have a more controllable monitoring situation.

Bass frequencies

Bass frequencies (below 150 - 200 Hz) will always need special attention when it comes to monitoring and room acoustics. Due to their very long wavelength and high energy, the bass frequencies behaves quite differently from mid- and high-frequencies. They are: 

  • more likely to put walls, furnitures equipments and such into motion causing rumble and noise from the resonating bodies.
  • tending to build up in corners and at edges and boundaries.

Bass Traps – are used to absorb unwanted resonating low frequencies causing either bass rumble or booming bass. Most often placed in the corners of the room. Anything that’s filling the corners will be an improvement in this matter. It’s worth to have in mind that lowering the speaker-level output will reduce the bass frequency troubles substantially.

Final Testing

Remember to test your monitoring system once more after you’ve taken all this considerations into account. As stated earlier in the article:
Testing means to listen for:

  • Bass – Tight & controlled or Uneven & muddy?
  • Stereofield – Wide & good separation?
  • High end – Smooth & crisp or Harsh and tirering?
  • Detailes – Do I hear all the details that the mix is containing?
  • SubWoofer – Is the low end (Sub-) frequencies coming through and giving the mix a distinct weight?
  • And do remember that testing the system should be done under normal conditions; that is with a suitable listening level (well under 90 dB SPL monitoring output). This yields to both testing and mixing, for not damaging your hearing and to not fatiguing your brain.

Summary

  • Select your monitors
  • Decide the optimal working position
  • Find the sweet spot
  • Adjust 2. and 3. to each other
  • Set up your monitors
  • Reducing unwanted reflections
  • Reducing unwanted bass responses
  • Test your setup.
  • Make some music!

Links

Monitors

Genelec
M-Audio
Tannoy

Techsites

Genelec Learning Center
Speakers construction
Difference between Hi-Fi and HD
ProSoundWeb
The Death of Dynamic Range
Pro Audio Reference
Audio FAQ

Want to know more?

Go to: - http://www.mixguides.com/studiomonitors/

JonBuer©2008