Pre-alignment delay values
Pre-alignment delay values
Time alignment from geometric measurements
When combining several loudspeaker systems, it is important to adjust their delay values to optimize acoustic
summation. If no acoustic measurement tool is available, it is possible to use the pre-alignment delay values given
in the tables on this section.
Pre-alignment delays have been measured with the enclosures at the same geometric location, front face on the
same plane.
After adding these values to the factory presets, time-alignment is then obtained by adding the geometric delay to
the closest system. The geometric delay is calculated from the path difference between a reference listening point
and the center of each system.
Laser rangenders
The L-Acoustics Tech Toolcase includes two laser devices that can be used for geometric measurements: TruPulse
™
200 (trademark of Laser Technology, Inc.) and Leica DISTO
™
D3 (trademark Leica Geosystems).
line source + separated subwoofer
Procedure
1. Measure the path difference: PA - PB, with:
P: reference listening point
A: center of the further system, named system a
B: center of the closest system, named system b
2. Calculate the Geometric delay(s): Path difference (m) / Sound velocity (m.s-1), with:
sound velocity ≈ 340 m.s-1 at 20°C and in dry air
3. Refer to the tables of this section to nd the Pre-alignment delay a and the Pre-alignment delay b,
corresponding to the system a + system b combination.
4. Add the Alignment delay to the factory preset of each system. Being the closest to the reference listening point, the
geometric delay must be added to the system b only:
a) alignment delay (ms) for system a = Pre-alignment delay a (ms)
b) alignment delay (ms) for system b = Pre-alignment delay b (ms) + Geometric delay (ms)
Normalization: If ≠ 0, subtract Pre-alignment delay a to both Alignment delay values.
66 Preset Guide owner's manual (EN) version 16.0
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