Harman JBL Professional VTX Series, Руководство пользователя

Страница: 28 / 33

28
VTX B 15 | User Manual
11.2 USING PERFORMANCE MANAGER
When in the field, Performance Manager’s Test System Mode can be used to test VTX systems. This method is quick, and especially
useful for determining whether all speaker cables, including cabinet-to-cabinet NL jumpers, are properly functioning.
To perform the test, Performance Manager uses the I-Tech HD’s built-in noise generator, in conjunction with the amplifier’s capabilities
to sense voltage and current draw, to generate a nominal load impedance reading for each amplifier output channel. Since broadband
pink noise is used as the test stimulus, the returned value is considered to be an average impedance value, which will differ from the
resistance values given earlier in this document, which are taken using DC resistance.
STEPS:
• To start the test, make sure Performance Manager is online and connected to the devices.
• Navigate to the TEST tab and make sure all speakers are muted.
• Switch the Noise Generator to the ON position and change the level to between -30 and -10 dB. Levels lower than -30 dB may
not be sufficient to trigger a reading.
• Unmute the speaker to start the measurement. The measured value is displayed on the speaker icons.
11.3 PERFORMANCE MANAGER READINGS
The measurements below show the expected impedance values for B15 cabinets, taken at room temperature with a cable length of 25
meters (82 feet). Acceptable tolerance is +/- 0.5 ohms.
The measurements recorded by Performance Manager are susceptible to drift based on variables such as temperature, cable length,
wire gauge, and usage conditions. Parameter variations such as temperature will be common across all B15 enclosures in use, so all
B15 subwoofers in a system should measure similarly. An enclosure measuring significantly different than others (by as much as several
ohms) indicates something wrong with that enclosure.
1
2
3
4
(1) VTX B15
TIP: The Performance Manager measurement uses an averaging algorithm in the background to generate a stable and
reliable impedance value. Measurements take time to stabilize. Continue running the measurement until the displayed
value settles.
(2) VTX B15 (3) VTX B15