LA 3200 | Installation Manual |
Bosch Security Systems | January 2004
EN |9
Determining mounting height and angle for the
LBC3200 loudspeaker array:
1.Determine the dimensions of the desired ‘listening area’
(a horizontal plane at the level of the listeners’ ears –
refer to the dashed line in figure 1).
2.Determine the angle at which the loudspeaker array is
to be mounted. The array is designed to beam sound
just above the listeners’ heads, and it is recommended
not to exceed an angle of 60. There are two approaches,
each with specific pros and cons.
•Approach 1: Maximized listening area
When a large listening area is desired, an angle of
round 30is recommended (see figure 1). Note that
when walking away from the loudspeaker array, the
sound pressure level will decrease by an amount that
depends on the room reverberation. To hear high
tones clearly, the listener should be able to see the
loudspeaker array.
•Approach 2: Minimized sound pressure level variation
When less sound pressure level variation is desired, an
angle of 50is recommended. Note that this reduces the
size of the total listening area compared to approach
1, and that the space very close to the loudspeaker
array (‘A’ in figure 2) is not part of the listening area.
Diagram 1 shows the relationship between 'A' and the
mounting height of the loudspeaker array when using
a 50installation angle.
3.After selecting the most appropriate approach
(mounting angle), the mounting height of the
loudspeaker is determined by focusing the 00-axis of the
loudspeaker array to the desired position just above ear
level of the furthest listener. This can be adjusted by
mounting the loudspeaker higher or lower on the wall.
Now you can mount the loudspeaker array for optimal
acoustic performance.
Installation questions and answers:
•May I install the LBC3200 loudspeaker array the
same as LBC3210 or LBC3201?
This loudspeaker array is designed for small and
medium indoor environments. The optimal acoustical
performance of this loudspeaker array is obtained by
beaming the sound just above the listeners’ heads.
When this loudspeaker array is mounted as the
LBC3210 or LBC3201, a very small listening area
results. This is also the reason for not using an angle
greater than 60.
• If I cannot see the loudspeaker array, does it mean
that I cannot hear high tones?
You can compare high tones with light. When
something is between you and the light source, you do
not see the light source with its full power. We call this
shadow. We have the same situation with high tones.
When a lot of people are sitting between you and the
loudspeaker, you are sitting in the sound shadow. We
experience that as a reduction of high tones.
Background information:
•Because of the many installing angles it is difficult to
give a defined shape of the radiated sound from the
loudspeaker array.
•By installing the loudspeaker array at a small angle, a
(very) large listening area can be reached. Depending
of the amount of reverberation in the room and the
sound shadow (people or objects in front of a listener
who are blocking the direct sound source) the speech
intelligibility on a far position may be low. In these
situations, it is better to use more loudspeaker arrays
to split the listening area.
•When you move further than the maximum position
of the listening area (more than the maximum
distance from the loudspeaker array), only the sound
pressure level will decrease. There is almost no tone
height variation. The decreasing of sound pressure
level depends strongly on the reverberation of the
room.
•When you are too close to the loudspeaker array (less
than the minimum distance from the loudspeaker
array) and are using the 50approach a decline of the
high tones will very soon occur.
•Because the loudspeakers are designed to beam the
sound just above the listeners’ heads, it is better not to
mount the loudspeakers too high above the listening
area.
•To determine exactly were the edges of the listening
area are in your situation, you have to carry out a
practical test at the location were the loudspeaker
array is installed. This is a job for an experienced
listener with well-trained ears. To do so, put pink
noise through the loudspeaker array. It is better to
reduce the lower tones for this test, as they do not
contribute to speech intelligibility. Walk around in the
listening area and listen to the high tones. The places
were the high tones decreases rapidly are the edges of
the listening area.
Listening area and related mounting height for LA3200/00
