Electro-Voice Sx600 User Manual page 13

System shuts down when driven hard.
1.) Insufficient amplifier power. Amplifier goes into protect mode due
to overcurrent or thermal stress. Switch to a larger amplifier.
2.) Line impedance too low. (PI models in particular) Some amplifiers
will not drive a 2 ohm load at full power, especially if both channels
are loaded to 2 ohms. (A pair of Sx600PI systems on the same line
is a 2 ohm load.) Use a different/bigger amplifier, convert to PIX
versions, or reconfigure lines with more amp channels and fewer
speakers per line.
3.) Incorrect high-pass filter or no filter at all. All Sx600 models MUST
BE HI-PASSED, (See step 5 above) but PIX models may cause
amplifier shut-down due to transformer saturation at high levels
caused by low frequency transients or heavy bottom octave pro-
gram content. Verify that the CORRECT hi-pass filtering is in use
at all times.
4.) Amplifier is simply being overdriven and going into protect mode.
With an oscilloscope on the amplifier output, adjust compressor/
limiter to keep amplifier(s) out of clipping. If the system has no
comp/limiter, add one to the signal chain and be sure it is properly
set.
Inconsistent intelligibility in audience area.
1.) Improper aiming. If intelligibility decreases near the speaker, the
down-angle is set too high. If the intelligibility is great right under
the speaker but suffers as you begin to move away from it, the
down-angle is set too low. Intelligibility across the horizontal plane
(side to side) can be affected by a sloping audience area, reflec-
tions from nearby walls or other barriers, and trees, banners and
other objects obstructing and/or reflecting the sound in an adverse
way. EASE is an excellent tool for predicting the correct aiming, but
in actual use these angles may need to be adjusted.
2.) Over-equalization. The primary speech fundamentals are found
in the 300Hz to 3kHz range, most consonants are affected by
the 3kHz to 6 kHz band, and sibilance is mostly from 6kHz on up.
Substantial EQ cuts in any of these regions will seriously degrade
the intelligibility of speech. Use only enough EQ to tame the very
worst room resonances (which should not be a problem outdoors)
keeping the notch width as narrow as possible. The best solution
is to keep the announcer close to the microphone and use a good
compressor/limiter to compensate for variances in microphone
distance and excitement.
Electro-Voice User Manual 11