XLA 3200 Installation Manual | EN 9 |
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Listening area and related mounting height for XLA3200/00
Determining mounting height and angle for the | • If I cannot see the loudspeaker array, does it mean |
LBC3200 loudspeaker array: | that I cannot hear high tones? |
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 30 is 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 50 is 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 50 installation angle.
3.After selecting the most appropriate approach (mounting angle), the mounting height of the loudspeaker is determined by focusing the
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.
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 50 approach 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
Bosch Security Systems January 2004
