Sound Design; Applications; Aiming Mtd Enclosures - L-Acoustics MTD Series Operator's Manual

5. SOUND DESIGN

5.1 APPLICATIONS

The art of designing a sound system is a profession in itself and a complete description of all sound
system design aspects is beyond the scope of this manual. If necessary, we recommend the use of a
specialized sound engineer or consultant since the best products can produce the worst results if
improperly set-up. In order to get the best results, it is important to follow correct sound design
principles, process your system with the appropriate LLC controller plus power amplification and
properly integrate your MTD enclosures with subwoofers.
In general terms, MTD108a, MTD112b or MTD115b enclosures are intended for distributed sound
reinforcement or small to medium-scale Front-Of-House (FOH) applications. FOH applications
include: theatres, clubs, multi-purpose venues or corporate events. Distributed applications include:
delay rings for large-scale installations, surround effects channels for theatre / multimedia, distributed
reinforcement for sports venues or delays for speech reinforcement in convention centre ballrooms.
Although optimized for single operation in distributed configurations, MTD loudspeakers can be used
in vertical or horizontal arrays of two enclosures to enhance either SPL or coverage.
Due to their compact, wedge-shaped format and axi-symmetrical directivity, MTD108a, MTD112b or
MTD115b enclosures also provide an exceptionally high performance floor monitor solution. When
used in conjunction with L-ACOUSTICS SB115, SB118 or SB218 subwoofers, MTD enclosures are
also suitable for side fill and drum monitoring applications.

5.2 AIMING MTD ENCLOSURES

Due to their controlled directivity behavior, MTD enclosures should be aimed so as to geometrically
cover the desired audience area with the main zero degree axis roughly orientated towards the
middle or rear of the audience area. Since the wavefront radiated by an axi-symmetric sound source
has directivity that is smoothly increasing with frequency, this helps to match coverage, frequency
response and SPL to the acoustic environment of a typical auditorium. Normally, the reverberation
time in auditoria decreases smoothly above 1 kHz and at greater distances in the venue, the low
frequency energy is fairly constant due to the reverberant field. Loudspeaker focus or aiming should
be adjusted so that maximum HF energy is directed towards the farthest listening areas – this helps to
balance the SPL attenuation with distance that occurs in the direct field. At closer listening positions,
the off-axis attenuation at higher frequencies provides a similar tonal balance and the overall SPL
attenuation with distance is less.
Although MTD enclosures have controlled directivity attenuation properties it is important not to
have the closest members of the audience too close to the system (i.e., in order not to produce
excessive sound pressure levels up close). Ideally, the ratio between the shortest and the furthest
distance covered should not exceed 1:4 and in order to achieve this, it is often desirable to fly the
system. However, when MTD enclosures are flown and the audience seating area begins very close to
the stage, it is oftentimes necessary to use distributed front-fill speakers (for example, MTD108a) or a
ground stacked left/right MTD stereo infill system in order to improve coverage and image localization
for the first rows of the audience.
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L-ACOUSTICS MTD Manual V1.2 11/30/2004