OPTIMIZING A SOUND SYSTEM
the first part of this article we
have listed ten factors which influence and determine sound reproduction
quality. Let's recall them:
1. Transport: CD player or
3. Vinyl disc or CD.
b) digital cables;
5. Preamplifiers and
6. Power amplifiers.
8. The room.
9. The power line.
We have said that
as we improve the sound of our system,
more and more refined and natural reproduction levels, all of the
factors are of paramount importance, for they
take on an equivalent
weight of around 10% of the
total sound quality.
is, if all these factors are optimized, they will
take on the same degree of importance regarding their action over sound
reproduction, for they will have the same
weight of influence
over the final results.
When considering the
“room” factor, we have said that whenever we refer to an “ideal”
reproduction room we report ourselves to a listening room devoid of
reflections or other aural interferences.
such a place,
the sound emanating straight from the loudspeakers reaches the listener.
In order to eliminate the possibility of existing reflective surfaces,
the “ideal room” would be the one presenting the largest possible
height, width and length dimensions. Taken to its ultimate consequences,
such a concept culminates in the set up of something utopian – a room
whose dimensions would be so large that its surfaces would be placed
extremely away from each other, in the “infinite”.
The “ideal room”, therefore, would
hypothetically be the open space itself (lacking any reflective walls).
For the time being,
however, and coming to “place
our feet on firm ground” again, we observe that our rooms are quite far
from the ideal room.
The fact is that the smaller our room’s
volume is, the greater the negative influence that its surfaces
cause upon the sound will be. And the room’s relevance will no longer be 10%
(as in the ideal case) but will range from 50 to 70%, with
respect to the final result, regardless either of its possessing the
so-called “golden dimensions” recommended by the acoustics or of its
containing first rate equipment. Therefore, the room becomes the most
important factor, acting directly upon the final sound results of a
sound system. In our last article we had stated that in a room of small
cubic volume, more than half of the success attributable to good sound
reproduction comes from the acoustic treatment applied to it. But what
should we do to make our room better?
In this field, opinions
and there is no consensus, not even among acoustic professionals.
This is because
acoustics is one of the most complex realms of physics and few know it
in some depth.
myself, it took me years
to realize this aspect.
I would endlessly replace equipment, tinkering with the electronics,
but I couldn’t come to the full results I had been hoping for and
feeling a little frustrated along the way for not having obtained the
satisfaction of reaching that ideal reproduction I sought so much.
I had graduated in electronic engineering, but the knowledge of acoustics I
acquired at college was quite poor. Since then, I have been learning about this subject from what I've read.
recently, I have dedicated myself to seek more information. When you
start to look for information on how to treat your room, you face such
an amazing array of treatment theories!
Some say you must “foam
these people guarantee this solves the situation.
Others disagree and say that
the room becomes too “dead” this way, and state that a room should be
neither “live” nor “dead”, but “semi-live”. Still others prefer
the solution suggested by Mr. Arthur Noxon and end up placing tubes everywhere, the so-called “Tube-Traps”. There are those who try
to treat all surfaces with special fittings, in an attempt to avoid any
type of reflection. And there are those who believe that random
reflections are the ones that indeed help make sound reproduction better,
and so place the largest possible number of objects inside the room, in
order to create countless reflective surfaces ! And so it goes on.. Doesn’t it
seem very contradictory to you?
What now? Which position should we
adopt? Where is the common sense? Which one makes the best cost/compromise
ratio? We will certainly need a very critical analysis in order to act
It is clear that amid
need a good acoustics
advisor to help you out !
© 2004-2008 Jorge Bruno Fritz Knirsch
Todos os direitos reservados
What to do?
Where to begin? Let us try to clear up
ideas. It seems logical and of good sense that we should try to come closest to
the ideal situation. We have seen that in an ideal room, only the sound
emanating from the loudspeakers reaches the listener. Therefore, our
procedure should be one that tries to guarantee that just the sound
emitted by the loudspeakers reaches the listener. This also means that
we should act in such a way as to eliminate or avoid any kind of sound
reflections or sound interferences that reach the listener and blemish the sound emitted by the loudspeakers.
In fact, reflections are
the greatest villains
enemies of good listening.
They are the origin of the sound quality
degradation we hear, for they get mingled with the sound coming straight
from the loudspeakers and end up distorting the recorded image we are
trying to reproduce. Reflections alter sound perception in the deepest
way. What steps, therefore, should we take ? First, I want to
suggest to you a simple operation: take out everything that is not
essential to the room. Take out the piece of furniture that is purely decorative, take out the aquarium,
if there is any and take out any superfluous objects. Of course I do
not propose here that you get into an argument with your wife, but may be
you will skillfully reach an agreement by explaining the
reasons for this procedure. We have already seen that the greater our
room’s free volume, the better the sound results of our reproduction
will be. Hence, we must not place any additional object there, because
besides diminishing free volume, we will be creating new reflective
surfaces. Dealing with wall, ceiling and floor reflections will already
be a challenge in itself, and just imagine if we create new surfaces on
each corner which, small as they may be, will reflect sound in a
disorderly way ! Then, instead of solving our problem, we will in fact
be creating a bigger problem ! Of course the greater the number of random
reflections we have, the less our control will be over the room’s
acoustics ! It would be ideal if our rooms were only used for
listening, isn’t it?
Try this experiment though. Perhaps you
may perform it on a calm Sunday evening. Take out of the room everything
possible and check how the sound changes. Experiment ! Check out the
soundstage ! This is a very interesting experience indeed. And besides,
it is much easier to treat acoustically an empty room than one full of
A second step to be taken
would be to define and delimit
our room a given zone or specific listening area.
the listeners going to sit ? Our goal here will be to analyze only those
reflections that could reach the listeners. By doing this we will also
be simplifying our problem, besides limiting our procedure only for what
we really want: to guarantee purity of sound for the listener.
Fig. 01 – Definition of
listening area for studying the reflections reaching the listeners.
If we were dealing with a recording
studio for example, our analysis would have to be different from the one
we will use here.
For us, the important thing is that the
listener is reached mainly by the sound that emanates directly from the
loudspeakers. However, reflections come to join the direct sound,
obviously at a time lag with respect to the direct wave, since they have
cross a larger distance before reaching the listener.
First reflections reach the listener
soon after he or she has captured the sound that comes straight from the
loudspeakers and then, the second reflections reach this listener a
little later, and
so it continues.
Do you know how we process all this
battering of sounds ? Our ears make a psycho-acoustic analysis of
everything that reaches us. In order to identify and take in what we
have captured, our ears mix and integrate into one whole chunk all the
sounds that are similar between themselves, even if they have been
captured at a spacing of up to some tenths of a millisecond. In other words,
our ears join and integrate similar sounds, even if they have occurred
at differences of up to some tenths of a millisecond, and consider them as
if they had occurred in one instant. I would like you to ponder a little about
this, so that you can understand what I am trying to show you, for it is
something quite serious for the results in sound ! Realize that direct
sound mingles with this same sound’s first reflection (whose intensity
is a little less than the one from the direct sound)…..and our ears
consider this as just one event!
It’s no surprise that without acoustic
treatment our system’s sound quality does not seem to be among the best
around, even if the equipment is first rate ! And many times we don’t
understand why the soundstage does not show up, or why the sound seems
flattened in but one plane, if we have been investing so much in our
system ! But the truth is that the soundstage can only exist if the
sound that comes directly from the loudspeakers dominates all the other
First reflections are the
ones most damaging to the sound and must be acoustically treated. For
example, the first reflections taking place in front of and behind the
loudspeakers affect soundstage formation on reproducing sound. On the
other hand, first lateral reflections are responsible for impairing
texture and tonal balance.
Another important aspect
that happens to our psycho-acoustic perception is the fact that the
second and third reflections reach our ears at times longer than
some tens of milliseconds, and present themselves in much lower
intensities than the ones coming from the direct sound.
are less relevant and are not being considered by us, for we cannot
understand them. In fact, they are “echoes” from the notes being played
that remain under reverberation in the room. So much so that acoustics
names this phenomenon “reverberating field”. The consequences of this
for the results of sound are quite disastrous, since sound
intelligibility is quite affected, that is, notes lose their sharpness.
This problem becomes more emphasized
larger rooms. The smaller the room, the lower the influence from this
According to the room’s
dimensions, other kinds of problems may
the appearance of reflections at low frequencies (in the range from 60
influence bass intelligibility. To the listener, when this happens, the
bass sounds resonant and “one-note-only”. This is a problem
that is difficult to solve.
on sound reproduction, reflections are the greatest villains, and
first reflections, when it comes to small listening rooms such as ours.
Initially it is necessary
that you determine the position
of your loudspeakers in a
definitive way. In order to help you on this task you may refer to a
very known website, the one from George Cardas, who is a sound cables
In this article he provides some parameters for positioning
loudspeakers in a room with “golden dimensions”. If memory does not
deceive me here, our dear Holbein Menezes has already commented on this
site on one of the articles of our then “Audio Club” (Clube do Áudio)
magazine, having published on that occasion the main figures and
directions presented by Mr. Cardas.
Only after having positioned the
loudspeakers you will be able to define and delimit the room’s listening
area, where listeners will be sitting. Only after this will it be
possible to discover, for each wall, the region where first reflections
will be taking place, the ones that reach the listening area. These are
the zones that must receive proper acoustic treatment.
Since the set of problems
for each place is unique, due to countless variations such as each
room’s dimensions, free volume, reflective surfaces, and aspects such
as whether the room is solely destined for listening or not, etc., I
recommend that you consult an engineer expert in acoustics. As you see,
there doesn’t exist a unique, standardized solution that is satisfactory
listening room. However, there are those who venture themselves in
providing standardized “solutions” – American magazine “Sound Advisor”,
for example, presents some kits for the acoustic treatment of first
reflections, that, from what I could check, are not always the most
suitable ones, and are also
We are now going to refer
to that question raised
the previous article:
you by any chance discovered which factor most influences sound results,
second to the “room” factor, the one we have just seen? What is your
Cheers to all, and…..good
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