Why use the SB-1 rather than delayed loudspeaker arrays?
Delayed loudspeakers are a common and effective alternative to long-
throw horns, but there are some constraints in their application.
As shown in Figure 1a, because the fill speakers are physically separated
from the main array(s), they can only be aligned for seats that lie
directly on their primary axis. For all other seats in their coverage area,
varying differences in path length from the main PA can cause
cancellations that degrade the frequency response. In small-to-moderate
sized installations, the path length differences are generally small
enough that cancellations occur only at very high frequencies. But in
large-scale applications requiring very long throws, cancellations can
develop in the upper midrange, where they can be much more
destructive of fidelity.
By contrast, because of its ability to project over very long distances,
the SB-1 can be placed with the main PA array. When the fill coverage
emanates from the same physical location as the main system, path-
length differences are eliminated, and flat response can be achieved
with far fewer system adjustments.
In enclosed performance arenas, delay speakers also excite the
boundaries of the space from multiple locations, producing uncorrelated
reflections that compromise intelligibility. This problem can be minimized
by carefully controlling the speakers’coverage patterns and band-
limiting their response, but only at the expense of complicating the
system design and its setup/alignment.
Because the SB-1 maintains consistent 10-degree coverage across its
full range of operation, it can be arrayed and aimed so that virtually all
of its energy falls on — and is substantially absorbed by — the
audience. Destructive reverberation is greatly reduced, the “critical
distance” substantially increases, and clarity is enhanced. Indeed,
listeners have commented that the SB-1 makes a large sound system
seem much closer to them, as though they were listening to studio
monitors in the near field!
How does the SB-1 work?
The SB-1 achieves a very narrow coverage angle and plane-wave
propagation by taking advantage of a large paraboloid reflecting surface.
A parabola is a simple, mathematically-described curve (Figure 2a) that
possesses a unique focal point. A paraboloid surface is formed by
sweeping a parabola around the primary axis that extends through
center of the curve and its focus, so as to describe a three-dimensional
dish. If sound energy radiates from a source at the focus and is directed
onto the paraboloid surface, it is reflected outward in a path parallel to
the curve’s primary axis (Figure 2b). The paraboloid thereby becomes a
highly directional emitter of plane (flat) wavefronts which are capable of
propagating over long distances with minimal loss — much like an
acoustic spotlight.
Despite the efficiency of parabolic reflectors, they have not been used
in sound reinforcement until now because conventional designs are
hampered by a limited frequency range (with substantial lobing in the
lower frequencies) and inconsistent beamwidth (varying with frequency).
The SB-1 addresses and overcomes both of these shortcomings.
Low-frequency lobing is controlled in the SB-1 by a 12-inch cone driver
SB-1Q&A continued
Meyer
Sound
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