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Room Acoustics 11
Your room is actually a component and an important part of your
system. This component is a very large variable and can dramati-
cally add to, or subtract from, a great musical experience.
All sound is composed of waves. Each note has its own wave
size, with the lower bass notes literally encompassing from 10’
feet to as much as 40’ feet. Your room participates in this wave
experience like a three dimensional pool with waves reflecting
and becoming enhanced depending on the size of the room and
the types of surfaces in the room.
Remember, your audio system can literally generate all of the
information required to recreate a musical event in time, space,
and tonal balance. The purpose of your room, ideally, is to not
contribute to that information. However, every room does con-
tribute to the sound, and the better speaker manufacturers have
designed their systems to accommodate this phenomenon.
Terminology
Standing Waves – The parallel walls in your room will reinforce
certain notes to the point that they will sound louder than the rest
of the audio spectrum and cause “one note bass”, “boomy bass”
or “tubby bass”. For instance, 100Hz represents a 10 foot wave-
length. Your room will reinforce that specific frequency if one of the
dominant dimensions is 10 feet. Large objects in the room such as
cabinetry or furniture can help to minimize this potential problem.
Some serious “audiophiles” will literally build a special room
with no parallel walls just to help eliminate this phenomenon.
Reflective Surfaces (near-field reflections) – The hard surfaces of
your room, particularly if close to your speaker system, will reflect
some waves back into the room over and over again, confusing
the clarity and imaging of your system. The smaller sound waves
are mostly affected here, and occur in the mid and high frequencies.
This is where voice and frequencies as high as the cymbals occur.
Resonant Surfaces and Objects – All of the surfaces and objects
in your room are subject to the frequencies generated by your
system. Much like an instrument, they will vibrate and “carry on”
in syncopation with the music, and contribute in a negative way
to the music. Ringing, boominess, and even brightness can occur
simply because they are “singing along” with your music.
Resonant Cavities – Small alcoves or closet type areas in your room
can be chambers that create their own “standing waves” and can
drum their own “one note” sounds.
Clap your hands. Can you hear an instant echo respond back?
You have near-field reflections. Stomp your foot on the floor.
Can you hear a “boom”? You have standing waves or large panel
resonances such as a poorly supported wall. Put your head in a
small cavity area and talk loudly. Can you hear a booming?
You’ve just experienced a cavity resonance.
Rules of Thumb
Hard vs. Soft Surfaces – If the front or back wall of your listening
room is soft, it might benefit you to have a hard or reflective wall
in opposition. The ceiling and floor should follow the same basic
guideline as well. However, the side walls should be roughly the
same in order to deliver a focused image.
This rule suggests that a little reflection is good. As a matter of fact,
some rooms can be so “over damped” with carpeting, drapes and
sound absorbers that the music system can sound dull and lifeless.
On the other hand, rooms can be so hard that the system can
sound like a gymnasium with too much reflection and brightness.
The point is that balance is the optimum environment.
Breakup Objects – Objects with complex shapes, such as book-
shelves, cabinetry and multiple shaped walls can help break up
those sonic gremlins and diffuse any dominant frequencies.
Dipolar Speakers and Your Room
MartinLogan electrostatic loudspeakers are known as dipolar
radiators. This means that they produce sound from both their
fronts and their backs. Consequently, musical information is
reflected by the wall behind them and may arrive, either in or
out of step, with the information produced by the front of the
speaker. The Script i was designed to minimize these rear wall
reflection interactions when it is mounted on a wall.
Now that you know about reflective surfaces and resonant objects,
you can see how midrange and high frequencies can be affected.
The timing of the initial wave as it radiates to your ears, and then
the reflected information as it arrives at your ears later in time, can
result in confusion of the precious timing information that carries
the clues to imaging. Consequently the result is blurred imaging
and excessive brightness. Soft walls, curtains, wall hangings, or
sound dampeners (your dealer can give you good information
here) can be effective if these negative conditions occur.
Your Room
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COUSTICS