Typical Load; Characteristics To Know And Understand; Specifications - Crown IQ-PIP-USP2 Reference Manual

The following example calculates the
SPL necessary for supervision of a
typical 8-ohm system. While the re-
sulting 80-dB SPL @ 1 meter is
definitely above conversation level,
it is not uncomfortable.
An "8 ohm" example:
30 mA into 8 ohms = 0.007watts
8-ohm driver sensitivity = 100dB for
1W @ 1 meter
0.007W/1W = –20dB
Required SPL for supervision test is
100dB – 20dB = 80dB SPL @ 1
meter

5.7.1 Typical Load

Characteristics to Know and
Understand
It is well known that the typical loud-
speaker impedance is not the same
for all frequencies. This variance is
due to the effect of electrical proper-
ties such as the expected increase
in impedance at high frequencies
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IQ-PIP-USP2
due to driver voice-coil inductance,
or the peaks and valleys due to
passive crossovers. Testing of vari-
ous passive boxes has shown peaks
of 100 ohms or more! Low frequency
impedance variation can come from
the interaction of the driver compli-
ance with that of the box. The low
frequency variations are usually wide
bandwidth and may vary from 6 to
30 ohms on an 8-ohm driver.
These anomalies are easily aver-
aged out by the IQ-PIP-USP2 super-
vision algorithm in most systems.
However, there may be some ex-
treme situations for very narrow
bandwidth (i.e. single-note) signals
and/or very widely varying loads that
the algorithm simply cannot over-
come. In these cases, widening the
high and low limits will help de-
crease the "sensitivity" of supervi-
sion and decrease chance of "nui-
sance" error reports.
IQ-PIP-USP2 Reference Manual
IQ-PIP-USP2

6 Specifications

General
Internal Controls: An 8-segment
DIP switch sets the IQ address (deci-
mal range: 1–250).* A 4-segment
DIP switch sets input and output
scaling. A Reset/Preset switch, ac-
cessible with a straightened paper
clip through the panel, selects
PIP
the next user preset if pressed for
less than 2 seconds, resets settings
to "factory default " if it is pressed
for more than 2 seconds, or re-writes
from firmware to flash memory re-
storing all settings to factory default
if it is pressed while applying power.
Jumpers select thru or processed
signal for daisy output of each chan-
nel.
Connectors: Crown Bus: RJ-45 con-
nector for input/output, RJ-45 con-
nector for daisy output. AUX In/Aux
Out/Listen Bus: RJ-11 connector.
Audio Input: Balanced 3-pin female
XLR connector for each channel.
Audio "Daisy Chain" Output: Bal-
anced 3-pin male XLR connector for
each channel.
Indicators: A yellow DATA indicator
flashes when a valid IQ command is
received from the IQ System via the
Crown Bus. The DATA indicator can
be forced on to facilitate rapid
troubleshooting of Crown Bus wir-
ing. A green PRESET indicator
flashes to indicate the user preset
number currently selected in
memory. If the PRESET indicator does
not flash the preset number when
* If address "0" is selected, the IQ-PIP-
USP2 will operate in stand-alone mode.
In this mode, the Crown bus port is de-
activated.
IQ-PIP-USP2 Reference Manual
selected, this indicates the preset has
been modified by the user.
Memory Backup: 1 Mbyte non-vola-
tile FLASH memory for backup of
run-time parameters, presets, and
program storage. Capable of 80,000
writes minimum.
Power Requirements: Power draw:
240 mA @ +24 VDC and 65 mA @
–24 VDC. When installed into a
Crown -compatible amplifier, the
PIP
unit receives ±24 VDC from the am-
plifier. No external power is required.
Total Power Dissipation: 7.4 watts.
Crown Bus Data
Communication
Protection: If communication is lost,
the unit will continue to function with
the last commands received.
Data Rate: 38.4 K BAUD.
Data Format: Serial, binary, asyn-
chronous; 1 start bit; 1 stop bit; 8
data bits; no parity.
Crown Bus Interface Type: Opti-
cally isolated 20 milliamp serial loop.
Operation: Half duplex.
Transmission Distance: Variable
from 200 to 3000 feet (61 to 914 m),
depending upon wire capacitance.
Typically 1000 feet (305 M) using
shielded twisted-pair wire, #26 AWG
or larger. Can be extended with an
IQ Repeater.
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