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5. Use the Suitable Cable Lengths guide (see pages 6 to 8) to confirm
the installed cable length is less than the value for the current that
was recorded in Step 3: Output Level and Clipping (4).
6. If the cable length does not exceed the value recorded in Step 3:
Output Level and Clipping (4), move on to Step 4: Field Uniformity.
If the cable length exceeds the value recorded in (4), the driver is
clipping. This means the loop connected is too long; therefore:
1. The system is not IEC60118-4 compliant.
2. The sound will be distorted.
3. The driver may be susceptible to damage and warranty voided.
Perform one of the following and repeat until there is no clipping:
1. Reduce the loop current,
2. Reduce the length of the loop,
3. Use a higher diameter of cable or flat copper tape,
4. Try a two-turn loop,
5. Use a higher voltage driver.
Step 4: Field Uniformity
1. Set up the FSM. Ensure that the two vertical arrows in the top-right
corner of the FSM are placed at the correct height:
•
1.2 metres (3’ 9”) for seated user.
•
1.7 metres (5’ 6”) for standing users.
A
tripod or similar for mounting the FSM is recommended.
2. Reduce the loop output current to 2 amps.
3.
Set the FSM to the RMS/Peak A-Weighted mode and record
the value measured by the FSM in the centre of the loop.
4.
Move the FSM to other user positions within the looped area
and record the values measured by the FSM.
5. The differences measured in other positions should not be greater
than +/- 3dB of that measured in the first position.
6. Repeat Step 4: Field Uniformity (3 to 5) to create a suitable map of
the area looped.
