User Manual

A White Paper Of The Installation Series Loudspeakers
1 Introduction
The ease with which a speaker system can be
adjusted to match the characteristics of a facility
is of the utmost importance to sound contractors
and engineers. In the same way that a painter's
canvas must be white in order to show the true
colors of his paints, a speaker system must be a
"white canvas" in the sense that it accurately
reproduces the waveforms provided as input and
responds in a linear fashion to equalization − in
audio terms it needs to provide a "flat response".
The two most common causes of such uneven
response are "comb filter" caused by the
installation or architectural condition and
"difference between the phase characteristics of
the speakers". The former must be considered in
the aspect of the system design such as speaker
angle, etc.
The latter should be considered as the important
matter for making the Yamaha speaker system as
"white canvas".
<Figure 1: Speaker measurement condition>
We made the simple test for measuring the phase
characteristics using two 2-way speaker systems.
Figure 1 shows the setting. Speaker system A has
60 degrees x 40 degrees (horizontal x vertical) of
the high frequency directivity, while speaker
system B has 90 x 50. The amplitude response is
almost the same. When driving both speaker
systems that have the same phase characteristics
simultaneously, the relative S.P.L. increases by
6dB at all frequencies, as shown in Figure 2.
We then changed the phase characteristics of
speaker system B and made measurement. The
result is shown in Figure 3. In the frequency
range where the phase difference is more than
120 degrees, significant cancellation is observed
in the amplitude response (you can see the
cancellation in the range where the phase
difference is between 120 and 240 degrees).
In the frequency range where cancellation is
observed, the equalizer does not respond in linear
so it is very difficult to improve the frequency
characteristics using the equalizer.
<Figure 2: Driving two speaker systems that have the same
phase characteristics>
Amplitude
100 1000 10000
Frequency [Hz]
Relative S.P.L. [dB]
Speaker A
Speaker B
A+B
10dB
Speaker A
6ft
6ft
Speaker B
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