TROUBLESHOOTING
VORTEX EF2211/EF2210 Reference Manual 42 Technical Support: 800.932.2774
— D/A, amplifier, loudspeaker, microphone, and A/D — to cancel acoustic echoes.
If you overdrive the loudspeaker or insert a dynamics processor before the echo can-
celler, the acoustic reflections picked up by the microphone do not match the signal
fed to the loudspeaker. They are distorted copies of this signal. The EF2211/EF2210
cannot effectively cancel this distorted signal.
If you suspect the loudspeaker is introducing nonlinearities into the room acoustic
path, take these steps to minimize its influence on the echo canceller.
• Keep the loudspeaker’s volume level at less than three-eighths of full scale. If
higher volume is required, the EF2211/EF2210 should operate effectively at vol-
ume settings of up to 50 percent of full scale. At more than 50 percent, most
audio systems and loudspeakers introduce significant nonlinearities. The
EF2211/EF2210 may not adapt under these conditions, and echoes may be heard.
• If the loudspeaker has a bass control, lower it. Excessive bass can cause a boomy
effect that is nonlinear. In addition, excessive bass may cause substantial
mechanical coupling to the microphone through vibrations induced in the hous-
ings and support structures.
• Increase the separation distance between microphones and the loudspeaker. The
EF2211/EF2210 handles up to 10 dB of room gain between the loudspeaker and
the microphone. You may be exceeding this limit if the loudspeaker is pointed
directly at the microphones or if the loudspeaker volume is excessive (loud-
speaker placement is not critical, but it should not be pointed directly at the
microphones).
C
ONTACTING
T
ECHNICAL
S
UPPORT
If these troubleshooting guidelines don’t resolve the problem you are experiencing
with the EF2211/EF2210, please check our web site (http://www.polycom.com) for
the most current technical support information (go to Products & Services, then to
Voice Products, then to Installed Voice Systems). If you have further questions,
please contact us at:
Applications Engineering
Polycom Installed Voice Business Group
9040 Roswell Road
Atlanta, GA 30350
Phone: (800) 932-2774
Email: vortex@polycom.com
Before contacting us, please review the warranty and repair policy on page 56.
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