User`s manual

"mpro" extension. This allows you to recall any value or file path later on by loading
this file again. Suppose you have a small production of ten speakers that you want
to test against a previous produced reference which you know is fine. You just have
to define and save a process that divides the current data with the reference.
Testing a device against itself should produce a flat line, within the frequency range
of the device, and this should be checked before saving the process. When you
need to check your batch you just recall your process. This will activate the
Automatic Process button. When this button is activated any subsequent
measurement is processed before it is displayed. The next process we will consider
is the dBSPL/Watt. It requires a file and an impedance value and allows us to
obtain a frequency response plot referred to 1W at the speaker terminal whatever
the real measurement level is. To make this possible an electrical measurement at
the speaker terminal (power amplifier output) must be taken, with dBV as y-scale,
and used as a reference file. A value of impedance is also necessary that allows
CLIO to convert voltage to power. We will go through the entire procedure using the
tweeter of the previous examples. Since what we are looking for is the response in
a 1W-1m condition we have to move the microphone to a distance of 1m from the
tweeter (it was at 69.14cm). The 1m condition can be set directly with a meter.
Fig.10.32 shows the 1m measurement in black and the previous one in red. Signal
level at speaker terminal is unchanged. The average difference being 3.3dB.
Audiomatica Srl MLS - Frequency Response 11/07/2001 18.49.03
CH A dBV Unsmoothed 51.2kHz 16K Rectangular File: ampout.mls
100 1k 10k 20k20 Hz
30.0
dBV
180.0
Deg
20.0 108.0
10.0 36.0
0.0 -36.0
-10.0 -108.0
-20.0 -180.0
C L IO
Figure 10.32 and 10.33
We now connect CLIO’s input to the speaker terminals and change the y-scale to
dBV, do not change CLIO’s output level, we then obtain Fig.10.33. This is a nearly
flat line that indicates the voltage delivered to the speaker. Remember to save the
measurement to disk. It is worth pointing out that deviation from linearity in this
curve due to the power amp or cable would be compensated for by this procedure.
Now we reload the response at 1m, go to the Process Dialog that will appear as in
Fig.10.34.
Figure 10.34
We set the impedance to 8 ohm as this is the nominal impedance of the tweeter.
Clicking OK we obtain Fig.10.35, which is the final result.
132 10 MLS & LOG CHIRP