Bosch Appliances XLA 3200 Listening area and related mounting height for XLA3201/00

XLA 3200 Installation Manual EN 11

Listening area and related mounting height for XLA3201/00

How to use these mounting method:

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.Measure the maximum distance from loudspeaker array to the last listener in the listening area (corresponding to ‘B’ in figures 1, 2 and 3).

3.Refer to diagram 1, and trace upwards from the maximum distance on the horizontal axis. From the vertical intersection with diagonal B-line, you go horizontal to the vertical axis. The X-value (height of loudspeaker array mounting bracket above the listening plane, ‘X’ in figure 1) is standing on this axis. The horizontal intersections with other diagonal lines provide information about the dimensions of the listening area. These numbers are related to figures 2 and 3 (see also example below).

4.Figure 2 shows the 1kHz octave shape radiated by the loudspeaker array and figure 3 shows the 4kHz octave shape radiation. The listening area with the optimal acoustic performance is in these shapes. Ensure the 4kHz shape with the dimensions obtained using diagram 1 adequately covers the desired listening area.

5.If the desired listening area is covered by the 4kHz shape, the X-value on the vertical axis show at what height the loudspeaker array must be mounted above the listening plane. Note that the loudspeaker array must be mounted at an angle of 80 at the chosen height!

Now you can mount the loudspeaker array for optimal acoustic performance.

Example:

The maximum distance from loudspeaker array to last listener is 15m. Tracing upwards from the 15m point on the horizontal axis of diagram 1 to the diagonal B-line and then sidewards to the vertical axis, the intersections with the other diagonal lines provide dimensions of the listening planes. In this example:

F-line (listening plane side length of 4kHz) = 11.1m C-line (listening plane length) = 11m

E-line (half width listening plane of 4kHz) = 9.3m A-line (minimum distance to listening plane) = 3.9m On the vertical axis, the X-value (the height between the listening plane and loudspeaker array mounting bracket) is 1.8m.

Installation questions and answers:

•The desired listening area is too large and does not fit in the 4kHz shape.

Try another loudspeaker array mounting height or use more loudspeaker arrays to get a larger listening area.

•Why use an angle of 80 for the loudspeaker array?

The radiated shapes shown in figures 2 and 3 with the dimensions in diagram 1 are only valid when the loudspeaker array is mounted at an angle of 80. Only this situation provides constant sound pressure level and frequency response (constant directivity) in the listening area.

•Can I use the loudspeaker array with another angle?

You can use the loudspeaker arrays also with another angle but you will not get the optimum acoustic performance. For example, greater sound pressure level variation will be audible in the listening area. The values in diagram 1 are not valid for other angles. It is recommended never to use an angle greater than 80.

•The loudspeaker array cannot be mounted as high as desired.

If not the height can be reached by limitation of the ceiling for example, use an angle of less than 80. Focus the 00-axis of the loudspeaker array to the desired maximum position (see figure 4). Note that the table in diagram 1 and shapes in figures 2 and 3 are not valid for this situation. Check in the listening area if the speech intelligibility is acceptable.

Background information:

•The shapes are defined in an anechoic environment. In these shapes at anechoic conditions, you have a maximum of 6dB sound pressure variation and much less perceived frequency response variation. In areas with normal or high reverberations, less sound pressure level variation take place and the size of shapes will be bigger. The perceived frequency response in this shape will then be almost constant.

•When you go further then the maximum position of the listening area (beyond the maximum distance from the loudspeaker array) only the sound pressure level will decrease. There is almost no tone height variation. The decrease in sound pressure level depends strongly on the reverberation of the room.

•When you move too close to the loudspeaker arrays (less than the minimum distance from the loudspeaker array) a lack of high tones will very soon occur.

Bosch Security Systems January 2004