L-ACOUSTICS XT Manual V1.1 2/11/2003 12
2. POWERING XT
It is important that power amplifiers with sufficient power are used to power the 112XT or 115XT
since headroom is less likely to damage loudspeaker components than clipping. Apart from normal
standards regarding construction, protection, cooling and damping factor that are expected of any
professional sound reinforcement amplifier, the XT system has been calibrated to be used with
amplifiers with the following specifications:
GAIN STRUCTURE
All amplifiers should have 32 dB gain for all sections (sub, low and high). The limiter thresholds and
output channel gains of OEM digital crossover presets have been adjusted to be used with amplifiers
having 32 dB gain
.
LIMITERS
Peak limiters on all amplifier outputs with soft clipping characteristics; attack time less than 3msec
COOLING
Temperature speed-controlled fan recommended
In practice, L-ACOUSTICS specifies power amplifiers with output power equivalent to twice the RMS
power handling for the low section and equivalent to the peak power handling for the high section.
These requirements typically allow the same amplifier to be used for both sections since the drive
level for the HF section is attenuated relative to the LF section to account for efficiency differences
(i.e., full continuous power will never be delivered to the HF section due to this attenuation). When
the same amplifier is used for the HF section, the extra available power then translates into headroom
for improved high frequency transient response.
Sections 2.1 and 2.2 give a summary of rms and peak power handling along with recommended power
amplifier output specifications for operation of single 112XT or 115XT enclosures or multiple XT
enclosures in parallel.
2.1 POWERING 112XT
Continuous (rms) and peak power handling ratings for the 112XT are as follows:
LF Section: 48 volts rms long term (pink noise with 6 dB crest factor)
290 Watts (continuous), 1160 Watts (peak) at 8 ohms
HF Section: 33 volts rms long term (pink noise with 6 dB crest factor)
135 Watts (continuous), 540 Watts (peak) at 8 ohms
Table 1: Load and Power Ratings for 112XT
112XT ENCLOSURE RATINGS
ONE 112XT TWO 112XT THREE 112XT FOUR 112XT
SECTION LOAD RMS PEAK REC'D LOAD RMS PEAK REC'D LOAD RMS PEAK REC'D LOAD RMS PEAK REC'D
LOW 8 290 1160
580
4 580 2320
1160
2.7 870.0 3480
1740
2 1160 4640
2320
HIGH 8 135 540
540
4 270 1080
1080
2.7 400.0 1600
1600
2 540 2160
2160
For amplifying 2 112XT in parallel, the recommended amplifier specifications are:
* LOW Amplifier Output Power: 1160 W into 4 ohms
* HIGH Amplifier Output Power: 1080 W into 4 ohms
For amplifying 3 112XT in parallel, the recommended amplifier specifications are:
* LOW Amplifier Output Power: 1740 W into 2.7 ohms
* HIGH Amplifier Output Power: 1600 W into 2.7 ohms
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