Loudspeaker placement for optimal sound quality according to the Joachim Gerhard principle
After putting together a high-quality music system, the room becomes a
limiting factor for the sonic performance. There are many articles and theories about
the optimisation of the interface between loudspeakers and the room as well as via
Methods for damping critical room resonances. Damping treatments
of room resonances with the aim of achieving a linear amplitude response are
usually costly and can lead to a "lifeless" room sound. Also the
Development of loudspeakers for a specific location, e.g. loudspeakers which
are intended for wall mounting, restricts the placement options
and leads to different results depending on the room size. Our approach consists of
to investigate how the room and the loudspeaker interact and to find the best
situation without making radical changes to the room.
need to be.
Our solution limits the interference of the space by a specific
speaker placement and listening position, and by using the effects of the
Psychoacoustics. This method provides excellent results without the need for a
special room treatment is required; a carefully applied
However, room treatment can bring about further improvement.
Let us first consider these findings about hearing. To
to find out where the sound is coming from, our brain records the time between the
the arrival of a sound in one ear and the arrival of a sound in the other ear, or
the interaural time difference (IAD). For example, if there is no difference in the
time it takes for a sound to reach each ear, the brain determines that
the sound emanates from directly in front of us. When the sound first reaches the right ear,
the brain determines that the sound is coming from the right, and so on. The place from
which the sound comes is determined by the delay time, and the
decision is made unconsciously and extremely quickly. In fact, the
Brain the position in the first 800 µs of the initial transient, as this is the
is the maximum time delay that can occur due to the distance between the left and the
right ear is possible.
After this initial sense of place, the perception of tonality begins.
It is believed that this is a crucial part of our survival as a
Species is. In other words, we first locate the source of a sound,
that could pose a potential danger, for example, and then try to
identify what made the noise.
Consequently, the first step in obtaining a good stereo sound image is to
the sound comes directly from the speakers to your ears before this sound is
is reflected. If the first sound pulse from the primary source arrives earlier than all the
reflections, this prevents any confusion about where the sound is coming from.
comes. The scientific term for this psychoacoustic phenomenon is called the
Haas effect. When the loudspeakers under anechoic conditions
have a smooth measurement result, the brain also perceives a smooth response,
when the first sound pulse arrives before the reflections. So even if measurements
show strong deviations in the frequency response of reflections at the listening position,
the brain will ignore this and perceive a linear response. From this
Therefore, one goal of loudspeaker placement is to eliminate the earliest reflections,
e.g. from walls or windows.
An idealized example of these principles would be a well-proportioned listening room in which
where the loudspeakers are positioned at the two focal points of an ellipse, the
touch the walls of the room, as shown in the figure below. The best
Listening position is centrally between the speakers, with the head 30cm to a
meters from the back wall. At this point the sound from the
speakers protect the ears from reflections from the side walls. The advantages are
the greatest possible distance between the loudspeakers for the widest possible
sound stage and a maximum delay of the first reflections. Thereby
the best soundstage and tonal balance are achieved.
The direct distance between the speaker and the ear should be at least one
meters should be smaller than the distance between the loudspeaker and a
reflective surface and the ear. The reason for the difference of approx. 1.6
meters lies in the fact that if the reflected sound 5 milliseconds or more after
the primary sound arrives, the brain knows that it is not the source. The sound
moves about 1.6 meters in 5 milliseconds. Here is an example of the formula for
Determining the best listening position. Assuming the distance between loudspeaker
and ear is 1.6 meters. Then the distance between speaker and
wall 1.6 meters and between the wall and the ear 2.6 meters, so that the entire
reflected distance is 4.3 meters. 4.3 meters for the reflection - 2 meters from the
Source = 2.3 meters. 2.4 meters is more than 1.6 meters. This corresponds to our ideal.
So why did we put the listening position near the back wall? The first
The reason is the bass amplification. The maximum sound pressure occurs at the room boundaries
and the pressure gives the feeling of a deep bass. Secondly, the brain can
not measure the time delay between the ears, because the reflections at the
back wall are shorter than the circumference of the head. If it does not measure the time delay
it can't locate the source of the sound. If the brain does not detect reflections
it ignores them.
Here are a few examples of how the brain can detect reflections or insubstantial
Information ignored. Imagine that you are at a noisy
public place and have a conversation with the person next to you. When you are talking from your
location, it would be muddled or look like it was taken from a
random sounds; however, you can isolate the conversation. When you
heard your name from a few meters away, you can focus
change and "listen in" on the other conversation. Another example is how we can change the
filter out the disturbing natural resonance of a corridor to hear speech better. In
a reflective acoustic environment, your brain automatically "listens" into the
Primary source "into" and ignores the reflections.
To sum up:
- Select the listening position so that the first sound that reaches the ears is directly from
comes from the speakers. Secondary reflections should arrive much later.
- Place the listening position at a distance of 0.3 to one meter from the rear wall.
away. In this way, the time during which the back wall reflections hit the ears
be too short for the brain to locate the source.
- After all, the wall is a spatial boundary, so that the perception of
deep bass is maximized when you sit close to the rear wall.
Let's expand the options for bass amplification by adding a method
which we call spatial mapping. This method detects
wave phenomena and takes into account the fact that the nature of sound propagation in rooms
is determined to a large extent by the room dimensions. The
Spatial mapping helps identify typical areas of bass cancellation
and amplification, so that we can use this information to better place the
speakers can use.
First, measure the room accurately and draw a simple
Floor Plan. Divide the room on the X-axis and on the Y-axis either into a
even or odd number of rectangles. At the intersections of the
lines you have drawn to divide, the bass amplifies with the even
division and weakens for the odd division. For asymmetric
spaces, the same applies approximately. To strongly asymmetric spaces later
Referring to the above example, the intersection points 2A and 2C are the ideal
Starting position for speaker placement. Position the listening position at B
less than one meter from the wall. This corresponds to the seating arrangement in the
If you want to place the speakers on the short wall, you can use a
good bass amplification by placing the listening position at line 2 against a wall.
and place the speakers at B1 and B3.
The next best speaker positions would be A1 and A3 or C1 and C3. You
can also place the listening position at line 2B and the speakers at A1 and A3.
Or set the listening position to line 2A and the speakers to C1 and C3. The
The disadvantage of these locations is a smaller distance between the loudspeakers, which
lead to a deteriorated sound stage and increased sidewall reflections
(which, as we have seen, can be problematic). Of course the
final arrangement is usually determined by the size of the room and the arrangement of the
furniture for sure, but if you put the speakers and the chair on a
equal division point of the room, you get a natural
Sometimes these arrangements lead to too much bass. According to the same principle can
you cancel low frequencies rather than amplify them. This way you get a
method of tuning the bass and mid-bass by adjusting the
Place speakers at odd pitch points of the room. The following
Figure is another drawing of a room, which is divided into odd gradations
is subdivided. The intersection points of the lines are the places with the lowest
It's important to remember that space is divided into far more than just quarters or
thirds of the bass can be divided. With even divisions, the bass is amplified
and with odd pitches, the bass is attenuated. If you use these grids
one on top of the other, you can see that small movements have a big influence
can have on the sound.
When tuning, there is a general tendency for sideways movements to affect the
mid-bass and forward and backward movements influence the low bass.
After determining the general ranking for the best low bass performance with
the room mapping technique described above, the next step is to,
to determine the distance between the speakers. When recording with
strong midrange information - a vocal or mono recording works well -
listen to the middle with the speakers slightly behind the listener's head
are facing each other. Move the speakers about 15 centimeters apart and
listen again. Continue until the middle image becomes thinner and more diffuse.
will be. At this point, the speakers are too far apart. Attach them
the place where the largest possible sound stage is created, without the
Energy of the center is lost.
Blind listening tests revealed that the preferred angle is 72° with the listener
at the intersection of the loudspeaker axes. However, the optimum angle depends
depends on the dispersion behaviour of the respective loudspeaker type.
The next step is to adjust the balance. First use a
Tape measure to achieve accurate positioning of the loudspeakers by
the distance between the tweeter of each loudspeaker and a specific
Measure the position on the listening chair. If the source and the electronics are set
are that both channels deliver the same output power, and the center sound
is not perfectly centered, it is usually because a loudspeaker is closer to the center.
on the listener than the other. Listen to a piece of music with a strong sound center
on. An excellent source for this procedure is a mono recording. If
the center is shifted to the right, the right speaker should be moved to the back or
the left one should be moved forward. Move only one speaker slightly
forward or backward until the image is centered. Often one centimeter small
The final step is to focus the soundstage. This is achieved by using a
speaker is rotated, which changes its radiation pattern at the listening position.
changes. This is much easier to do with two people. Start
with both loudspeakers directed slightly behind the listener's head, and
play music with a pronounced middle. While the listener listens intently
(sometimes it helps to close your eyes), the other person turns a
Speaker around the inside front corner (possibly the spike). Pay attention to the
size of the instruments and their overall "energy". Normally shows a stronger
focused "energetic" image indicates the best location. The listener should be a signal
to indicate the best focus.
When this is done, neither speaker needs to be set so that
he "mirrors" the other. The reason that the speakers may be
are not symmetrical, lies in the fact that rooms are not symmetrical and the
reflections that affect the radiation are not symmetrical. From this
reason, different speaker angles can compensate for spatial anomalies.
The radiation pattern also varies depending on the loudspeaker and
Crossover design. For example, Suesskind and Joachim Gerhard are
Collection speakers are designed so that their off-axis reproduction is similar to their
is on-axis playback. This eliminates problems with sidewall reflections
and their angle of incidence is reduced in comparison to loudspeakers with radical
different on- and off-axis response not so critical.
Here is a summary of the setup steps:
- Place the speakers for the best bass response. Move the
Front to back speakers for low bass and side to side for mid bass.
- Change the distance between the speakers to increase the width of the
to optimize the sound stage.
- Move a speaker to adjust the balance from left to right.
- Adjust the angle of the speaker to achieve the best focus.
Here are some additional recommendations:
- Since adjustments are reciprocal, you can get more performance out of your system.
by repeating this adjustment procedure for "fine tuning".
- If you sit with your head close to a wall, something slightly
damping material, such as a small tapestry, or the like, placed directly behind
you're comfortable with, improve the sound.
- If you move your head forward and backward, you can at one point
between the wall and one meter away changes in the perceptible
Listening to Sound Energy. As mentioned in the discussion of the bass range, are
Space Boundaries High Pressure Areas. When the pressure is high, the
speed of the sound wave is lower. If you move a little further away from the wall
remove, the system sounds a little more "alive", but the bass effect decreases. You
can adjust your listening position to adjust this.
- When fine-tuning for tonal balance, the initial
Angle the speakers the sound quite a bit. Listen to the difference
between a speaker aimed directly at your ear and a loudspeaker,
which is aligned straight ahead without an angle of incidence. This way you can reach up to
to some degree, adjustments for a bright or dull room
make. As a rule, loudspeakers aimed directly at the listener sound
are more extended in the high frequencies, because the frequency response on the axis
has less treble drop. When the speakers are pointed straight ahead, the
the off-axis reproduction results in more sound energy being
is reflected, and the image becomes more diffuse.
We hope that our guide will help you to optimize your
Speaker placement helps and gives you a better understanding of the stereo sound
has made possible. The best way to understand this information is to listen and to
experiment. Have fun with it.
Soon this guide will be followed by an addendum, in which we will go further into
Room imaging, strongly asymmetrical, L-shaped and very small rooms Rooms and
the impression of the acoustic image in the height.