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12. Subwoofer setup procedure
The M 7200 SW's extensive setup options let you
fine-tune the subwoofer very precisely to your
listening environment. To calibrate your system,
you will need the sound level meter and test CD
shipped with the system, and a blank frequency
chart (see page 35). Photocopy the chart so you
can re-use it in the future.
Before you commence the calibration process, fa-
miliarise yourself thoroughly with the M 7200 SW
THX Select subwoofer's controls and settings(see
Chapter 11). An extensive range of options is pro-
vided to fine-tune the subwoofer to your room, so
make sure to know exactly what they are before
you begin using them.
About the Teufel Test CD
The CD contains a reference level track, as well as
45 further calibration tracks with a duration of
30 seconds each. Each of these tracks contains
a sine wave signal at a different frequency. The
first is Track 02, at a frequency of 15 Hz. The sub-
sequent tracks are arranged as a rising series of
frequencies up to 190.49 Hz, with each track be-
ing a semi-tone higher than the previous one.
The frequency spectrum was divided into semi-
tones because of their musical properties. The
human ear can easily differentiate between semi-
tones, and the relationship between them can be
applied to any part of the frequency spectrum.
The mathematical relationship between the in-
dividual semi-tones is 21/12 (i.e., 1.05946309).
The test CD's frequency steps correspond to the
frequency controls on the M 7200 SW THX Select
subwoofer.
Once you have familiarised yourself with all
the components, follow the steps described
below:
Step 1: Connect the subwoofer to the corre-
sponding Pre Out/Sub Out on your AV receiver
and connect the mains power cable.
Step 2: Connect a CD/DVD player to your receiver
and insert the Teufel Test CD.
Step 3: Press the "On/Standby" button to acti-
vate the subwoofer. If the CD's bass signals are
already playing, the subwoofer should now be re-
producing these.
Step 4: Calibrate the subwoofer's output volume
using the supplied sound level meter. To do this,
place the level meter at the main listening spot
and point it directly at the subwoofer. Next, start
32 Teufel · LT 7
the test CD and adjust the subwoofer's volume
level. Make sure never to alter the position or di-
rection of the sound level meter during the cali-
bration process.
Please be aware that the supplied sound level
meter is a very simple device which is not as ac-
curate as a professional signal analyzer. If you re-
quire high-precision audio signal measurement,
we recommend purchasing a suitable measuring
device separately.
Set up the sound level meter as follows:
Remove the protective tab from the
4
battery.
Set the weighting to "C"– only the "C"
4
setting is suitable for measuring
the entire frequency spectrum.
Set the response to "Slow" .
4
Set the range to "70" .
4
Start the test CD.
4
Step 5: Switch on your CD/DVD player, insert the
Teufel Test CD, and play Track 01. This contains a
test tone at a frequency of 100.91 Hz. Track 01 is
designed as a reference track for you to calibrate
the levels of the subwoofer and the meter. At the
listening position, the sound level meter should
be reading a level of 75 dB (75 dB is also at the
centre of the y-axis on the frequency chart tem-
plate). Adjust the subwoofer's level in reference
to the readings from the sound level meter.
Step 6: Take the blank frequency chart and a pen
and sit down in your main listening spot with the
sound level meter. You are now ready to measure
the frequency response curve.
Step 7: Start the testing sequence by playing the
test CD and measuring the levels of the succes-
sive test frequencies. Record your measurements
by plotting them on the frequency chart.
The test tones contained on the test CD corre-
spond to the frequency values on the x-axis of the
frequency chart. Track 02 (the lowest sine tone
and first testing tone) starts the frequency spec-
trum at 15 Hz; Track 46 ends it at 190.49 Hz. For
each test tone, plot the measured level as a coor-
dinate point, and move on to the next frequency
by skipping to the next track on the test CD.
Step 8: Connect the coordinate points you have
plotted in the chart to produce a frequency
curve. The test chart on the following page shows
a sample frequency curve.
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