Legacy Audio Whisper XDS - Manual (Page 24)

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(They are a total of six factory trained technicians in the U.S. that travel to
setups if requested. They are based in Los Angeles, Orlando, Chicago, New York and here in Springfield.)
nd order differential to be exact) that might be built which could operate with
one diaphragm directly behind the other. Signals from the two baffles are combined acoustically with time compensation to steer the low frequency wave
-launch forward, while creating a progressively reduced acoustic output to the sides until reaching a null at 90 degree off axis. This eliminates boundary
interactions from sidewalls, ceiling and floor. The gradient acoustical pressure reaching the listener at each ear contains far less room noise, allowing the
brain to lock in on the natural ambience in the recording.
Designer’s Notes
(From Bill Dudleston)
The ideal speaker would stop and start on cue regardless of the combinations of frequency and level. It would have the same radiation pattern through-
out the spectrum. It would sound as true to the last voice in a large choir as it would a soloist and never overload.
Back to reality. For a given size diaphragm the displacement requirements for uniform output increase by a factor of four for each octave dropped
(frequency halving). Unfortunately distortion is proportional to displacement. Meanwhile transient integrity (waveform tracking ability) is reduced as dia-
phragm displacement requirements increase with the sound pressure level.
A single panel speaker with a thin diaphragm will beam at high frequencies, exhibit traveling waves across its surface, reflect at the clamped edges, have
limited excursion and behave inefficiently at lower frequencies. While they can also be sensitive to rear wall placement, the lack of upper bass colora-
tion is appealing, lending an ‘open’ quality to the sound.
Mount instead a woofer and a tweeter in a cabinet and you have the issue of polar tilt with comb filtering (alternating constructive and destructive inter-
ference in the region of overlap). This is due to the asymmetry and lack of an acoustic center. Even if the crossover provides an in-phase relationship to
the seated listener, it cannot be in-phase relative to its many reflection paths. The tweeter radiates broadly at the crossover frequency while the woofer
is beaming narrowly in comparison. Additionally, if you decrease the resonant frequency of the woofer to provide deeper bass, the efficiency drops with
the tracing speed.
But what if the drivers were arranged symmetrically? And the resonant woofer enclosure eliminated? And the bass drivers were replaced with four, lar-
ger, low mass diaphragms? And these low mass diaphragms were given several milliseconds of a head start to keep pace with the higher frequency sec-
tion? And the speaker had virtually the same acoustic radiation pattern at all frequencies? And the system was immune to early sidewall reflections? And
multiple listeners could share in the sweet spot? And the frequency response could be tailored to the room and negate the effects of the furniture? And a
nice guy was willing to show u
p at your house and tune them for you?
The Whisper XD S design radically increases piston area in the forward plane extending bandwidth, sensitivity, and frequency range. Because the design
is open air, the system is virtually free of enclosure resonance and room limitations. Whisper XD S’s differential alignment is analogous to a dual element
mi- crophone. Audio pioneer, Harry Olson, suggested a loudspeaker design ( 2
The sweet spot is much wider with the Whisper XD S design, allowing the listener to move outside the left speaker and still hear a balance with the
right speaker, and vice versa. Our manual recommends a strong toe-in, to cast the strongest acoustic shadow across the face. It explains that the
imprint of the shadow of the nose into the opposite ear is the other portion of the stereo signal that is usually washed out by excessive room
reflections with con- ventional speakers.
Whisper
XDS