Testing Vtx B18; Using A Dmm (Digital Multimeter) - JBL VTX Series 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 the utmost reliability, it is important to confirm that the system is operating within spec-
ified tolerances to ensure optimal performance for years to come. Below are two methods that can be used to check and verify proper
transducer performance in a VTX B18 system.
14.1 USING A DMM (DIGIT AL MUL TIMETER)
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 operating within their standard tolerances. This test is ap-
propriate for individual boxes, 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.
B18 functioning
Driver shorted
Notes:
• The DCR numbers listed above assume cold (room temperature) transducers. If measurements are taken right after use, when the
transducers are warm, the values will vary from those given above. For best results, test the speakers cold.
• The DCR value of a transducer gives an accurate representation of its electrical state. Mechanical defects are not characterized by
this test. Refer to the VTX B18 Service Manual for instructions on diagnosing mechanical problems by performing a rub and-buzz
test using a sine wave generator.
B18
DCR Tolerance
4.5 Ω +/- 0.5 Ω
0.2 Ω -
B18
Compact Single 18" Subwoofer
IN/OUT IN/OUT
A B SN
Channel Selection
VTX B18 | User Manual
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