EAW D S A 2 5 0, D S A 2 3 0 4 . 4 E n g i n e e r i n g D e s i g n, 4a Angled Radiation Pattern

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

4 . 4 E n g i n e e r i n g D e s i g n

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.

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

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.

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