Proceedings of the Institute of Acoustics
Vol. 25. Pt 4. 2003
Table 1. Small two way controls.
Control type
Room response control settings, dB
Treble tilt
0, –2
Bass tilt
0, –2, –4, –6
Bass roll-off
0, –2
Table 2. Three way controls.
Control type
Room response control settings, dB
Treble level
0, –1, –2, –3, –4, –5, –6, driver mute
Midrange level
0, –1, –2, –3, –4, –5, –6, driver mute
Bass level
0, –1, –2, –3, –4, –5, –6, driver mute
Bass tilt
0, –2, –4, –6, –8
Bass roll-off
0, –2, –4, –6, –8
Table 3. Two way controls.
Control type
Room response control settings, dB
Treble tilt
+2, 0, –2, –4, driver mute
Bass tilt
0, –2, –4, –6, driver mute
Bass roll-off
0, –2, –4, –6, –8
Table 4. Large system controls.
Control type
Room response control settings, dB
Treble tilt
+1, 0, –1, –2, –3
Treble level
0, –1, –2, –3, –4, –5, –6, driver mute
Midrange level
0, –1, –2, –3, –4, –5, –6, driver mute
Bass level
0, –1, –2, –3, –4, –5, –6, driver mute
Bass tilt
0, –2, –4, –6, –8
Bass roll-off
0, –2, –4, –6, –8
3
ROOM EQUALISATION OPTIMISER
Optimisation involves the minimisation or maximisation of a scalar-valued objective function
E
(
x
)
,
)
(
min
x
E
(1)
where,
x
is the vector of design parameters,
x
∈ℜ
n
. Multi-objective optimisation is concerned with
the minimisation of a vector of objectives
E(x)
that may be subject to constraints or bounds. Several
robust methods exist for optimising functions with design parameters
x
having a continuous value
range
37
.
3.1
Efficiency of Direct Search
The room response controls of an active loudspeaker form a discrete-valued set of frequency re-
sponses. If the optimum is found by trying every possible combination of room response controls
then the number of processing steps becomes prohibitively high (Table 5).
Table 5. Number of setting combinations.
Type of loudspeaker
Room Response Control
Large
3-way
2-way
Small 2-way
Treble
tilt
5 - 4 2
Treble level
7
7
-
-
Midrange level
7
7
-
-
Bass level
7
7
-
-
Bass tilt
5
5
4
4
Bass roll-off
5
5
5
2
Total
42875
8575
80
16
3.2 The
Algorithm
The algorithm
38
exploits the heuristics of experienced system calibration engineers by dividing the
optimisation into five main stages (Table 6), which will be described in detail. The optimiser consid-
ers certain frequency ranges in each stage (Table 7). A screenshot of the software graphic user in-
terface can be seen in Appendix A and a flow chart of the software can be seen in Appendix B.
