Voice Coil 2019 07.pdf

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V O L U M E
3 2 ,
I S S U E
9
J U L Y
2 0 1 9
IN THIS ISSUE
Industry News & Developments
By Vance Dickason
Klippel Controlled Sound (KCS)
1
INDUSTRY NEW &
DEVELOPMENTS
Electroacoustic Measurements
of Headphones
8
By Vance Dickason
SPOTLIGHT
By Christopher J. Struck
13
Loudspeakers are highly nonlinear and time-variant systems.
Signal distortion, heating, aging, climate, and other external
influences limit the maximum level and the quality of the
reproduced sound. Klippel Controlled Sound (KCS) represents
a new paradigm in active loudspeaker control and correction
(see
Figure 1).
The adaptive nonlinear control system, KCS,
can cope with these undesired effects and generate the desired
linear behavior over the entire working range.
Moreover KCS provides:
•
•
•
•
•
•
More sound pressure output
Active protection against overload
Cancellation of nonlinear distortion
Desired linear target performance
Copes with aging, climate, and production variance
Lowers cost, weight, and size
DIRECTORY
By Nora Wong
Adhesives, Coatings, Sealant,
and Dispenser Providers
Loudspeakers for Vented Enclosures
A Backward Approach for Speaker Selection (LoVE BASS)
By Francisco Castells and José Manuel Requena
18
SPOTLIGHT
TEST BENCH
By Vance Dickason
22
Faital Pro’s New 6RS140
and TB Speaker’s W8-2314
36
INDUSTRY WATCH
By Vance Dickason
Figure 1: Graphic representation of the KCS operating features over
the dynamic range of a transducer
October 18 • 19 • 20, 2019
Nansha Grand Hotel • Nansha China
Consumer
•
Commercial
•
Audiophile
Musical Instrument
•
Professional
Meet directly with the best suppliers • Find all of your loudspeaker solutions
Technical representatives available • Chinese business service advice
Headphone and microphone suppliers
www.loudspeakersourcingshow.com
VOICE COIL
T
HE
T
EAM
PRESIDENT:
CONTROLLER:
EDITOR:
KC Prescott
Chuck Fellows
Vance Dickason
INTERNATIONAL EDITOR:
EDITORIAL COORDINATOR:
GRAPHICS:
ADVERTISING COORDINATOR:
João Martins
Shannon Becker
Grace Chen
Nathaniel Black
S
UPPORTING
C
OMPANIES
ACO Pacific, Inc.
AES Headphone Show
ALMA International
BMS Speakers GmbH
FaitalPRO
HEAD acoustics, Inc.
Hernon Manufacturing, Inc.
Kisling AG
LaVoce Co., Ltd.
27
9
33
3
31
11
17
15
23
Loudsoft, Ltd.
Menlo Scientific, Ltd.
PanaSound, Ltd.
Solen Electronique, Inc.
Tectonic Audio Labs
Loudspeaker Sourcing Show 2019
Vance Dickason Consulting
Wavecor, Ltd.
25
39
31
21
40
2
17
37
NOT A SUPPORTING COMPANY YET?
Contact Peter Wostrel (voicecoil@smmarketing.us, Phone: 978-281-7708, Fax: 978-281-7706)
to reserve space in the next issue of
Voice Coil.
July 2019
Head Office:
KCK Media Corp.
Phone: (434) 533-0246
P.O. Box 417, Chase City, VA 23924
ISSN 1521-091X
Subscriptions:
Voice Coil, The Periodical for the Loudspeaker Industry, is published monthly by
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4
VOICE COIL
Figure 2: Block
diagram of the KCS
signal processing and
feedback loop
The adaptive control structure is based on electro-
acoustical modeling and combines real-time monitoring of
the transducer parameters with active protection against
thermal and mechanical overload, nonlinear distortion
cancellation, system alignment, and stabilization of the voice
coil position.
These features lead to an extension of the usable working
range to increase bass and sound pressure level (SPL) or
allow transducers to be made smaller, lighter and more
cost effective. Additionally, transducer design can focus
on increased efficiency by reducing parameter linearity to
create a new generation of Green Speakers producing more
acoustical output and less heat by requiring less energy.
Figure 3: Comparison of typical transducer THD with and
without KCS
KCS is a self-learning system that is based on a nonlinear
physical model that provides an adaptive software solution
with automatic parameter identification and that provides
online learning with any audio signal. This new process
uses the transducer itself as the sensor to identify the
instantaneous transducer parameters by monitoring voltage
and current at the speaker terminals. The nonlinearities
indicate the transducer’s usable working range, eliminating
time-consuming tuning by a human expert.
While playing music in online mode, KCS constantly
monitors voltage and current at the speaker terminals to
continuously adapt the internal model with time varying
transducer properties (e.g., variances of mechanical stiffness,
voice coil temperature and voice coil position). Based
on the identified parameters, the nonlinear transducer
model estimates precise state information such as voice coil
displacement, which is required by the protection systems.
Figure 2
provides a block diagram of the overall KCS process.
A Self-Learning System
Figure 4: Block diagram of KCS distortion reduction methodology using mirror filters
KCS provides real-time distortion reduction
that is based on a nonlinear physical speaker
model such that linear and nonlinear distortions
are reduced (see
Figure 3).
Due to the continuous identification of
transducer variances, the behavior is kept
constant over the speaker lifetime. Nonlinear
and time-variant transducer parameters
will cause nonlinear and linear distortion in
the transducer’s output signal. KCS uses a
nonlinear filter structure, which is a mirror
image of the determined transducer model as
depicted in
Figure 4.
JULY 2019
5
Distortion Reduction

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