HPI
18LP
User Manual
User Manual
HPI Series
HPI18LP
5
Avoid Amplifier Clipping
Bearing in mind the previously described
principle of amplifier power being higher
than speaker power, keep signal levels low
enough so that neither the Clip or Limit Active
indicators are blinking frequently or are on
continuously. If they are, turn down the input
signal level.
A low power amplifier that is clipping will
quickly damage the loudspeaker.
The Secret to Long Life
A competent audio system operator will
operate the loudspeaker within its limits.
Operation beyond the loudspeaker’s
capabilities usually includes, but is not limited
to, one or more of the following conditions:
1. Amplifier clipping
2. Noticeable distortion
3. Mechanical noise (such as a cone
bottoming out)
4. The gain to the amplifiers is increased with
no audible increase in sound pressure level
(power compression).
At a minimum, the operator should have a
meter display on the mixing desk calibrated to
indicate where the amplifier’s maximum RMS
voltage limits will be reached.
How to Calibrate the Mixer VU
Meter
With the loudspeakers disconnected, turn up
the mixer with program music until the mixer
VU meter ind3dB on peak. Check
the amplifier status lights and if the clip light
appears intermittantly the VU meter will be a
guide as to available amplifier power.
The purpose of this test is to determine at
what point of the mixer VU amplification, the
amplifier is at full power. Depending on signal
path, this could be anywhere between 0dB
and +6 on the mixer VU.
Finding a Suitable Amplifier
The HPI18LP is an 8 ohm enclosure and can
be connected in multiple parallel connections
to an amplifier channel that can operate into
speaker impedances of 4 ohms.
A recommended power range per amplifier
channel is 2,000 watts RMS into a 4
Ω
load.
(Two HPI118LP boxes per channel in parallel
connection). An ideal partner for the HPI18LP
is the Quest QA3004 or QA4004 amplifier.
Setting the QA amplifier’s high pass filter at
35Hz is recommended for clean high SPL
applications.
Loudspeaker Wire Gauge
The proper conductor size (wire gauge) to
use for the loudspeaker cable is primarily
a function of the wire length. The general
rule is that lower resistance, in relation to
the loudspeaker’s impedance, is better. To
achieve this, use larger conductor sizes
for longer lengths of cable and for lower
impedance loudspeaker loads. For wiring
cables to sub bass boxes, 2.0 - 2.5mm 14
Gauge would be the minimum for short cable
runs.
Standard AWG
•
14ga ... 0.6410” dia = 1.63mm dia
10.44ohm/km
•
16ga ... 0.0508” dia = 1.29mm dia
13.17ohm/km
•
18ga ... 0.0403” dia = 1.02mm dia
20.94ohm/km
Euro Standard Wire
•
1x1.00mm2 = 18 ga AWG
•
1x1.50mm2 = 16 ga AWG
•
1x2.50mm2 = 14 ga AWG
•
1x4.00mm2 = 12 ga AWG
