Ivie IE-45 RTA - Real Time Analysis - Manual (Page 32)

Ivie IE-45 Manual
page 32
Polarity
Polarity
The Polarity feature of the IE-45 allows the user to test for the polarity of a loudspeaker with respect to the sig-
nal source, or with respect to other loudspeakers.
Normally, in a correctly wired system, positive voltage on the “+” output of the signal source (amplifier) should
generate outward speaker cone travel (away from the speaker housing and magnet). More important to the per-
ception of the listener is the uniform polarity wiring of all speakers in a system.
The IE-45 can help the user to quickly test for correct polarity. In order to test for polarity, a pulse must be gen-
erated and sent through the speakers to be tested. The IE-45 can generate the special pulse needed to do the
polarity test, though it may be desirable to generate the pulse external to these units (see Tip #2 below). To
generate the pulse from the IE-45, connect the output (Q1 earphone output = 3.5 mm phone jack) to an input in
signal processing chain going to the speaker system. From the Polarity screen (Function > Polarity), tap the
“Pulse On” button in the lower part of the screen. A special pulse will begin to repeat.
In order to make a valid test, the IE-45 microphone should be in the direct field of the loudspeaker. As you
move the microphone close enough to a loudspeaker to be in the direct field, the Polarity display will show “+”
Positive Polarity, or “-” Negative Polarity, or “- - -” No Lock. “Positive Polarity” means that the system is wired so
that the loudspeaker is correctly reproducing the output of the amplifier with regard to polarity. “Negative
Polarity” means the opposite. “No Lock” means that the microphone is either “confused” because it is not in the
direct field and is seeing too high a level of reverberant energy relative to the direct field, or the overall level of
the speakers is not sufficiently above the room’s noise floor. These conditions can be corrected by either mov-
ing the microphone closer to the speaker or raising the output level of the loudspeaker.
The most important function of the Polarity test is to assure that multiple loudspeakers in a distributed speaker
system are wired so as to be of uniform polarity. By starting the pulse signal and then moving from the direct
field of one speaker to the next, the user can quickly confirm that the speakers are correctly wired for uniform
polarity. The following tips may also prove useful:
Tip #1
When speakers are mounted in a ceiling more than eight feet above the floor, it may not be possible to move the
microphone into the direct field of the speakers when the microphone is mounted to the IE-45 (unless the user is
on stilts!!). Using a microphone extension cable and a means of elevating the microphone closer to the speak-
ers can provide the solution (a broomstick and some tape works very well!).
Tip #2
Often, using the pulse generated by the IE-45 can be impractical, since a long microphone extension cable, or a
long output cable, or both, might be called for in order to get the pulse signal into the sound system while simul-
taneously moving the microphone close to the speakers. In most cases it is easier to use a separate pulse
source instead of the IE-45. There are several ways this can be done.
One way to do this would be to record the pulse and play it back to the sound system with a player. Another
would be to use the .wav file of the pulse provided on the CD that comes with the IE-45.
Yet another way would be to use an external generator that creates a pulse that is compatible with the Polarity
feature of the IE-45. The Neutrik® “Minirator”, for example, generates such a pulse.