L-Acoustics LA15a, Руководство пользователя

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L-ACOUSTICS LA15a 115V Manual V1.0 27/01/2003 12
Second, the maximum expected average current under worst case conditions, corresponding to 1/3
full power program material according to the FTC standard. At this level the music will be in a state of
constant clip and is therefore the highest power level one can obtain without completely obliterating
the program material.
Third , the normal operating power, as defined by the safety standard IEC 65/ANSI/UL 6500 and used
by a majority of safety agencies. The normal operating power is measured using pink noise, with an
average output power equal to 1/8 of full power. The 1/8 full power specification is as loud as you can
play music while making some attempt to avoid obvious clipping and corresponds to 9 dB of
headroom (which is very low for normal audio program).
Table 4: LA15a Maximum Output Power versus Mains Input Power
MAXIMUM OUTPUT POWER MAINS INPUT POWER
Load # of ch Power 1/3 Power 1/8 Power Idle
(watts) (see note 1) (see note 2)
8 ohms 4X 370 1140 820 175
4 ohms 4X 380* 1325 840 175
2 ohms 4X 500* 2125 1440 175
note 1
Mean power with music as program source (amplifier driven to clip level)
note 2
Normal music power with 9 dB headroom (IEC standard power rating)
*MLS switch set at -3 dB
It is recommended that you specify your power distribution service to ensure sufficient current for at
least 1/8 power operation and to upgrade service to meet 1/3 power requirements for heavy duty
demands like discos etc.
5.6 HEAT POWER CALCULATION
The heat power can be calculated according to the following example:
Consider headroom of at least 9 dB (1/8 of full power) and a 4 ohm load on an amplifier producing
380 watts per channel. The 1/8 power per channel is then: 380 / 8 = 47.5 watts; and the total output
power is : 4 x 47.5 = 190 watts.
The power consumption according to Table 4 is 840 watts (Table 4 gives the active power
consumption of the amplifier for different loads and power levels).
The
heat power produced is the difference between the power consumption and the output power:
840 - 190 = 650 watts per amplifier.