Transducer Issues - QSC K8 Service Manual

9.10 Transducer issues

There are many different types of failures for transducers in K series loudspeak-
ers. The most common issues found are the following: spider becomes unglued
from the frame, cone tears near the surround, burnt voice coil (because of a BOP
failure), and voice coil rubbing on edge of magnet. These are often manufacturing
issues but they do not occur very often.
Symptoms:
• missing or intermittent high and/or low frequencies
• distorted sound
Failure verification:
• tears in cone or surround, glue application issue, magnet damage, or other
obvious transducer failures
• open circuit measured across the transducer's terminals
• Can hear obvious distortion when powering the transducer with a sine-wave
tone using a separate amplifier (not the BOP).
Repair notes:
• On top-box models, the low frequency transducer can be replaced without removing
the baffle.
• On the KSub, the only way to remove the low frequency transducers is through the
back by first removing the BOP. There is no access from the front.
Note: Foreign objects can enter the KSub through the front grille/wood panel. These
objects can stick between the magnet, frame, and cone, which can result in a very
distorted sound.
• Always apply gasket around the rim of the low frequency transducer where it will mate
to the surface of the enclosure. Poke holes in the gasket material over the mounting
holes in the frame.
Important note: When refastening the low frequency transducer to the baffle, tighten
the screws in a crisscross pattern. Be careful to not damage the surround on the re-
placement transducer when you insert the screws, because it cannot be repaired except
by replacing the entire driver...again!
• To replace the high frequency transducer, the baffle should be removed.
• All K-series top-box models share the same HF transducer.
• A diaphragm replacement is available for the HF transducer. Use QSC p/n SR-000145-00
• Note the wire color in the table below for each model.
LF+ wire
K8 green
K10 green
K12 green
KSub green
• Before attaching the grille, do a quick test on the loudspeaker. Plug a low-distortion audio sine wave generator into a
1/4" or XLR input on the amplifier module. Gradually sweep the frequency from 20 Hz to 20 kHz. All frequencies should
be audible and free of distortion or rattling. You should notice the sound crossing over from the woofer to the horn at
about 2 kHz.
TD-000487-00
K Series Service Manual
LF- wire HF+ wire
green/black yellow
green/black yellow
green/black yellow
green/black
Figure 9.14 - LF transducer
Figure 9.15 - HF transducer
HF- wire
yellow/black
yellow/black
yellow/black
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