JBL VTX B18 Series, User Manual

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VTX B
18 | User Manual
14 - TESTING VTX B18
Speakers need to be periodically checked and maintained in order to assure long-term performance and reliability, and the VTX B18 is
no exception. While the system is designed for utmost reliability, it is important to confirm that the system is operating within specified
tolerances to ensure optimal performance for years to come. Below are two methods that can be used to check and verify proper trans-
ducer performance in a VTX B18 system.
14.1 - USING A DMM (DIGITAL MULTI METER)
This method is best suited for when the speaker system is in the shop. A DCR (DC resistance) test with a multimeter can give a very
accurate reading of how many transducers are properly wired together and within their standard operating tolerances. This test is ap-
propriate for individual boxes and not groups.
With the B18 speaker unplugged from any amplifiers, set a DMM to the resistance (Ω) setting and place the probes across the Pin1+/-
and Pin 2+/- leads. Record the values indicated on the DMM for each pair of leads and refer to the chart below to either confirm correct
readings or investigate out-of-tolerance DCR readings.
Notes:
• The DCR numbers listed above assume cold (room temperature) transducers. If taken right after use, and when the transducers are
warm, the numbers will vary. For best results test the speakers cold.
• The DCR value of a transducer gives an accurate representation of its electrical state. Any mechanical defects are not character-
ized by this test. Refer to the VTX B18 service manual for instructions on how to perform a rub-and-buzz test using a sine wave
generator.
B18
DCR Tolerance
B18 functioning 4.5 Ω +/- 0.5 Ω
Driver shorted 0.2 Ω -
B 18
Compact Single 18” Subwoofer
IN/OUT IN/OUT
A B
Channel Selection
SN