CLIOwin 7 PCI User's Manual - Audiomatica

etween true phase, as in Fig.10.22, and minimum phase. It is exactly what we need
to separate the time of flight from the devices own phase response. We won’t use
excess phase directly here but a post process of it, Excess Group Delay. Fig.10.25
is the excess group delay of our tweeter vs. frequency.
110.0
CLIO
7.50
dBSPL
ms
100.0 6.00
90.0 4.50
80.0 3.00
70.0 1.50
60.0 0.00
20 100 1k Hz
10k 20k
Figure 10.25
It was obtained by selecting Excess in Drop Down Menu. This graph represents the
distance of the sound source from the microphone vs. frequency. As long as the distance
is constant the system is minimum phase and we are in the position of a well defined
acoustic centre. If you recall from previous paragraphs we have reliable data down to
200Hz because of the time windows. As we deal with a tweeter we will consider the
2k-20k frequency range where the marker reads a constant 2.01ms. We will use this
value to operate a time shift that removes the sound flight time. This is accomplished
from the Processing Tools Dialog, selecting Time shift and typing the value we found
as in Fig.10.26.
Figure 10.26
Clicking OK we can finally display the processed phase, minimum phase and magnitude
response of our device in Fig.10.27. We used the term "processed phase" here and this
is not casual.
122 Chapter 10 - MLS