User Manual

Speaker System Design Guide for
Yamaha Sound System Simulator
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0
100 1000 10000
[Hz]
[dB]
Figure 5: Measured and computed results at X = 6, Y = 6
Blue: Y-S
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. Red: Measured results integrated over 15 ms. Pink: Measured results integrated
over 100 ms. (The measured results are moving averages.)
¾ Evaluation of High-Frequency Drop-Off
Figure 6 shows the computed and measured results at point B (x = 1 m, y = 10 m).
Point B is approximately in the center of the seating area. The blue line represents
the Y-S
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computed results. The red line represents the measured results in the
actual hall. It shows the values integrated over 15 ms after the reception of direct
sound. The spectrum of the measured results was acquired through an 8192-point
Fourier transform and then converted into 25-point moving averages. The vertical
axis of the graph represents relative sound pressure levels, and the maximum
value for each line is set to 0 dB.
In the Y-S
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computed results (blue line), there are no dips in any particular
frequency bands, but the frequency characteristics decline steadily starting at
approximately 4 kHz. The reason that the frequencies that are subject to phase
interference are rather high is because the difference between the distances
between the two speakers and point B is small.
This high-frequency drop-off also appears in the measured results at the actual hall.
In the values integrated over 15 ms (the red line), the characteristics begin
declining at approximately 2 kHz. They decline by as much as 20 dB. The dips
observed at point A that were caused by reflected sound from the floor do not
appear in the same frequencies at point B. The reason for this is probably that the
ways in which sounds are reflected are different at the two points because the
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