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Should the subwoofer have an inverting amplier
(rare) or be sited well away from the LS50 Wireless
II such that the output is not in-phase with that of
the LS50 Wireless II at crossover, there is the option
to invert the signal to the subwoofer. In this case the
appropriate toggle should be set to ON. More usually
it is set to OFF. The correct setting will provide a fuller
sound.
If no subwoofer is used the high-pass lter to the LS50
Wireless II should be bypassed by switching the toggle
in the app to OFF.
The correct sub gain setting depends on several
factors such as the sensitivity of the subwoofer and
how many are used. The correct balance may be set by
ear.
Syncing with Vision
Should the speakers form part of a home theatre
installation, where the programme content is
audiovisual, the thorny question of the sound syncing
with the picture (so-called lip-syncing) must be
addressed.
The all-pass characteristic of the bass/midrange to
tweeter crossover adds delay to the tweeter, so any
correction, if it is to be causal, must delay the whole
signal. Additionally, wireless transmission adds some
delay. It is important that all this inherent delay
does not lead to the perception of mis-syncing, even
if theoretically it is impossible to keep everything
absolutely together for all settings.
The Advanced Television Systems Committee (ATSC)
recommends that the sound to vision delay tolerance
is between -15ms to +45ms if lip-syncing is to be
unnoticeable. The maximum delay through the speaker
is comfortably less than 6ms and so lip-syncing should
not be a problem, whatever the settings chosen in the
app.
Firmware
From time to time, like any software-controlled device,
it will be necessary to update the LS50 Wireless II
rmware, to improve security, add functionality or
correct bugs.
Fortunately, the user needs to do nothing. If there is an
update available, it will be automatically downloaded
from our servers overnight, if the devices are either
fully on or in standby.
If preferred, users can manually download updates at a
time to suit them using the app. It is also not necessary
for the interspeaker cable to be connected.
The KEF Connect app will also receive updates, the
process of updating/setting automatic updates will be
dependant on the smart device.
Power Amplication
As a true active loudspeaker, LS50 Wireless II features
four individual ampliers - one for each drive unit in
the system. These sit after the crossover, meaning that
each amplier receives only the frequencies destined
for the corresponding driver. This differs from a
passive or powered system, where the crossover
comes after the amplication.
A signicant benet from a design standpoint is that
different ampliers can be explored for each drive
unit. Through intensive computer modelling and
listening tests, KEF engineers were able to develop
amplication that is perfectly matched for the
frequencies - and drivers - at hand.
LS50 Wireless II features the same amplier classes as
the original LS50 Wireless - Class AB for the tweeter
and Class D for the midrange/bass driver. However, a
number of changes have been carried out, owing to
improved R&D and driver improvements.
The Class AB high frequency amplier sports a totally
new topology - not only providing a higher output,
but distortion and dynamic capabilities have been
further enhanced over the original. The Class D mid/
low frequency amplier has also seen a signicant
increase in power output.
Summary
All too often, active speakers simply add power ampliers and active crossovers to a passive design, but there is
much more that active drive can offer.
This speaker takes an already excellent passive design and benets from all the acoustic technology packed into
it. The inherent benets of Uni-Q are improved upon even further through the inclusion of Phase Correction,
whilst the lack of a physical crossover eliminates what can be a signicant source of distortion.
LS50 Wireless II also represents a loudspeaker system equally driven by the concept of ‘Let You Be You.’
LS50 Wireless II does not aim to change the way someone experiences their music, but is designed to elevate the
individual’s unique situation through access to a plethora of music services and personalised EQ settings. Further
features and improvements, where developed, will be available through easy to perform rmware updates.
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