How to Interpret the Graphs (Continued)
Deciding the time period for Advanced EQ Setup calibration
When you are using Acoustic Cal EQ calibration (instead of EQ Professional calibration), the input data from the microphone is analyzed at fixed time periods from 80 to 160 msec (the red area in Figure 1). Advanced EQ Setup allows you to choose a point (20 msec width) in the range from 0 to 80 msec (the blue area in Figure 1).
Note
You can specify the time period setting using the “Advanced EQ Setup” in the “EQ Professional”
Figure 1 Comparison of microphone data acquisition time periods
Level |
|
(dB) |
|
Acoustic Cal | Acoustic Cal EQ |
EQ Professional | calibration range (fixed) |
calibration range |
|
(selectable points) |
|
Time (in ms)
To decide the time period for Advanced EQ Setup calibration, view the graphs of the measured reverb characteristics, and refer to the following three patterns.
Pattern 1: Different reverb characteristics for high and low frequencies
In rooms with reverb characteristics like those shown in Figure 2, lower frequencies often seem overly reverberant compared to higher frequencies (i.e. the room sounds ‘boomy’). If you calibrate the receiver using the Acoustic Cal EQ setting, data will be acquired in the 80 to 160 msec range (the red area of Figure 2). The analysis concludes that low frequencies are too loud and high frequencies are too soft, so it adjusts the equalization curve to strengthen high frequencies. In fact, however, the high frequencies may already be loud enough if measured within 40 msec, which is the time it takes for sounds coming directly from the speakers to reach your ears. Therefore, the Acoustic Cal EQ may result in a room where high frequencies sound shrill. In cases like this, setting the time period for Advanced EQ Setup to 30 to 50 msec (the blue area in Figure 2) to adjust for sounds coming directly from the speakers can flatten the frequency response for direct sounds (including initial reflections) and give a
Figure 2
Level (dB)
Low frequencies
High frequencies
Time period 
point to be
selected
Time (in ms)
15