CLIOwin 7 PCI User's Manual - Audiomatica

esolution you get is calculated as the sampling frequency divided by the FFT size. Again
for the default settings this is 48000/16384=2.929 Hz. This is already a high resolution.
However thinking in terms of octave or fractions of an octave, which are the terms of
a logarithmic frequency axis, 2.929Hz is around 1/2218 of an octave at 10kHz while
is around 1/3 of an octave at 10Hz.
Again an example is better than a thousand words. We will measure a twin T notch filter,
probably the most demanding situation for frequency resolution, with two sizes 8k and
64k, and two centre frequencies, 10k and 63Hz. Results are in Fig.10.7.
Audiomatica Srl MLS - Frequency Response 06/07/2001 15.02.28
20.0
180.0
CLIO
dBV
Deg
0.0 108.0
-20.0 36.0
-40.0 -36.0
-60.0 -108.0
-80.0 -180.0
20 100 1k Hz
10k 20k
File: fig3a.mls
CH A dBV Unsmoothed 51.2kHz 65K Rectangular
Figure 10.7
Interestingly, while we took four measurements we can only effectively see three
curves. In actual fact the 8k size gives by far enough resolution at 10kHz and the
associated curve is completely hidden by the 64k one. The 64k curve (Red) only differs
from the 8k curve (blue) at 63Hz. We have seen that there is another parameter
involved here, which is sampling frequency. While experimenting with it, we will also
make our first impedance measurement. We will use CLIO internal mode. This is again
the default setting, so all we have to do is to change the Y scale units to Ohms. We are
going to measure a big 15" professional woofer using 51.2kHz and 6.4kHz leaving the
size at 16k. The output level is set at +12dB. Fig.10.8 and 10.9 shows the results.
Chapter 10 - MLS 115