Your Room is an Instrument (pre-mastering)

sati

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#1
(posted on DSCI -- thought you ladies might be instested as well)

Your Room is an Instrument

One oft-overlooked and absolutely crucial aspect to the mixing/pre-mastering process is the room you are working in.



The ASC Attack Wall


You have an empty room, and that's if you are lucky. Correctly position your speakers (hopefully you atleast have some cheap "studio monitors") first.

Setting Up Speakers In A Rectangular Room

by George Cardas

Very precise speaker placement can open up a whole new dimension in listening, so I will outline the system that is becoming the standard of the industry. This standardized listening room is a Golden Cuboid and is the model for the math used in this system. This method will work with any box speaker, in any reasonably sized rectangular room. You may find that you have already positioned your speakers this way by ear.

Active nodes are the main concern when placing speakers in a rectangular room. A node, or the frequency where speakers and parallel walls interact, is proportional to the speaker to the wall distance.

The three most importance nodes, in order of importance, are proportional to the distance between the speaker and:

1. The side wall nearest the speaker
2. The rear wall
3. The side wall across from the speaker

A secondary factor is the speaker-to-speaker time constant.

When you use this Golden Ratio method to set your room up, the speakers are placed so the three nodes progress or differ from one another in Golden Ratio. This eliminates any unison or near unison resonance in the nodes.

Panel or dipole speakers such as Apogees and Magnepans cancel their side waves, so a formula of .618 x the ceiling height can be used for determining placement from the rear wall. Most box speakers radiate low frequencies in all directions thus a formula that places the speaker to rear wall distance at 1.618 the side wall distance should be used.

Speaker placement, simply stated

The distance from the center of the woofer face to the side walls is:

Room Width times .276 (RW x .276)

The distance from the center of the woofer face to the wall behind the speaker is:

Room Width times .447 (RW x .447)

This is all you need to know to place speakers in a symmetrical, rectangular room!


Placing Speakers in a Rectangular Room


Notice you are working against the shortest wall in the room -- this is important! Follow the link in the caption for the above diagram if you must position your speakers against the long wall [not optimal.]


Did you see that ASC Attack Wall in the picture just below my intro? Now you need to think about reflection (empty room?) and absorption (or a lack thereof...)

That's probably $8,000.00/₤16.000 worth of Tube-Traps (used to abosorb lower frequncies as well as reflect or absorb high frequencies depending on which side is facing the sound source.

It does two major things:

1) Reduces reflections like slap-back/flutter [read: echo] as well as early reflections (those reflections coming from the surface just behind [or closest to] the sound source.) Notice the monitors are sitting within a similiar looking device, this is (I believe) an attempt to reduce early reflection.

2) Reflects from certain points to retain a sense of acoustic space. No one listens to this stuff in an anechoic chamber. Meaning it's important not to over-do it and end up with an "acoustically dead" mixing environment.


Anechoic chamber - From Wikipedia, the free encyclopedia


Also, it's always good to have a sound-absorbing surface on the wall directly in front of you [to reduce early reflection] as well as the two side-walls. A little wall coverage on each wall (don't forget the floor/ceiling) will go a long way towards damping unwanted reflection!


Auralex absorption panels and a bass-trap


What about the BASS?

Your [rectangular] room has three frequencies that you are probably unaware of. These correspond with the dimnsions (width, length, and height) of your room. These are frequencies that will develop as standing waves within your room. Eventually you will be compensating for the existance of these, whether you are boosting bands which are lost due to interference with standing waves or directly reducing frequencies around the harmonics of your room (creating a weak band in your mix.) This translates to a mix that sounds good on your system, but not so good on others. (It's important to note that reflection of high frequencies [discussed previously] also contributes to this.)

The formula for determining the fundamental frequency of a standing wave for a particular room dimension is:

fo = V / 2d

Where:

fo = Fundamental frequency of the standing wave

V = Velocity of sound (1130 feet per second)

d = Room dimension being considered in feet (length, width, or height)

Hermholtz Resonator


What do you do about them? Well, you could follow the link in the caption for that ancient looking device above and create one specifically for your room -OR- you can try some Bass-Traps in the corners...


Bass-Traps

These come in a lot of flavors, but traditionally they are corner-mounted, composed of insulation, and designed to convert low-frequency vibrations into heat. Use them to "tighten" the bass response in your room. Sub-woofer recommended!


A Do-it-yourself Bass-Trap


...And remember to decouple your monitors from your desk or mixing console! You can use 4 glass beads that have one flat side (used in fish-tanks) or you can buy some MoPADs from Auralex. They keep your monitors from turning your desk into another sound source!



Good Luck!

(sati)
 
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Indi

Tha Original ThreadKilla!
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#4
Good post (y)



There's a thread already in here somewhere that tells you how to soundproof your recording room cheaply and effectively.
 
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