16
Finding the f
S
of a Raw Speaker Driver
The f
S
is the speaker's natural resonant frequency. This will
give you some idea of the usable bandwidth of the speaker.
Generally the speaker will not produce usable output below
the frequency of f
S
.
1. To measure the f
S
, make sure the driver is ready to be
measured (read General notes for measuring raw
speaker drivers on page 8).
2. Connect the test leads to the speaker, if it has multiple
voice coils they all need to be connected. Connecting
the coils in parallel will work fine.
3. Turn on the IM-SG by holding the
On
button for 1
second.
4. After the unit is operating, adjust the frequency to the
low end of the f
S
range in the chart below. Then slowly
raise the frequency until the peak in impedance is found.
If you go too far and pass the peak, just back down the
frequency until the peak in impedance is found. Figure 1
shows the impedance curve for a 15 inch woofer we
tested. We measured the f
S
to be 24Hz.
5. Record the Frequency where the Impedance reaches its
maximum value within the range of interest. This
Frequency is the f
S
.
Typical values for f
S
are listed in the table below to give you
an idea of where to look for it.
Speaker Type
f
S
Range
Subwoofer
10 - 50 Hz
Midbass
20 - 150 Hz
Midrange
30 - 900 Hz
Tweeter
400 Hz - 5 kHz
Summary of Contents for SMD IM-SG
Page 1: ...IM SG Impedance Meter Signal Generator Owner s Manual ...
Page 20: ...20 Figure 2 Impedance curve of a typical 4 ohm 1 tweeter Notice the fS at 1 59 kHz ...
Page 22: ...22 Figure 3 fC of a single 4 ohm 15 inch subwoofer in a 2 cubic feet sealed box ...
Page 44: ...44 Notes ...
Page 45: ...45 Notes ...
