Eaw DSA250 & DSA230 User Manual download pdf (Page 14)

4.4 Engineering Design

The core acoustical design of the DSA Series dates back to the late 1930s in

Harry Olson’s book, “Acoustical Engineering”. He showed that, by using

different signal delays on the input to each transducer in a simple line array,

the array’s main output lobe could be effectively “steered”. While this

concept has certainly been used before, the design of the DSA Series goes far

beyond this simple concept.

The engineering design for the DSA Series is certainly capable of “steering”

the main output lobe, as per Olson. However, the shape of the lobe in the

vertical plane is also variable. This allows changing the depth of the

coverage to precisely fit the listening area thereby reducing troublesome

near-to-far SPL differences.

A major advantage of DSA is the character of its radiation pattern. Contrary to

what might be intuitively assumed, the DSA’s radiation pattern is not the same

as simply down-tilting a loudspeaker that has the same horizontal and vertical

beamwidths. The example EASE plots illustrate this difference.

The radiation pattern of the conventionally, down-tilted loudspeaker has at

least two problems. The geometry of the pattern results in inadequate

coverage across the front area of the room. It also focuses a distinct line of

energy along the side wall. This energy is nearly at the same loudness as the

floor seating area. The sound reflections off the upper part of the wall will

arrive at many listeners late enough to impair intelligibility. These

reflections add to the direct sound and cause the higher intensity sound

seen at the rear , even though these areas are further from the loudspeaker.

By contrast, the radiation pattern of the DSA loudspeaker is far more consistent

across the entire floor area. The energy it directs to the sidewalls is not only

lower in level, but creates a very different reflection pattern. The sound reflected

off the wall will be largely directed down into the floor or nearby listeners along

the sides, arriving early enough to actually enhance intelligibility.

Ver: 30° Hor: 120°

Lspk: S1

Project: DSAMultipurpose-Tilt

Map: Direct SPL

Freq: 5000 Hz

[Third Octave Average]

Shadow Cast: No

Resolution = 1.0 m

Ver: 30° Hor: 120°

Lspk: S1

Project: DSAMultipurpose-Steer

Map: Direct SPL

Freq: 5000 Hz

[Third Octave Average]

Shadow Cast: No

Resolution = 1.0 m

Figure 4.4a Angled Radiation Pattern

Figure 4.4b DSA Steered Radiation Pattern

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Eaw DSA250 & DSA230 User Manual Page 14

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