Kef LS50W User Manual

LS50W

Frequently Asked Questions

The LS50W is an amazing engineering feat. Our engineers have taken the

unrivaled-in-its-class performance of the LS50 passive speaker and turned it in to

a completely self-contained (and mighty powerful) music system. The technologies

used in the LS50W are all state-of-the-art and perfectly matched to high-fidelity

systems costing hundreds, if not thousands of dollars more.

AUDIO

Does the LS50W use the same driver as the LS50?

Yes. From a sonic standpoint, the LS50W is identical to the LS50 passive. Great care and effort was put in to ensuring
the LS50W had the same sonic signature as the LS50 passive. LS50W uses the same 5.25” Uni-Q driver array inside a
symmetrical cabinet design with constrained layer damping.

What is the upper frequency output range of the LS50W?

As is typical with our Uni-Q drivers, the upper frequency range is near at, up until well over 40kHz – twice the frequency
of even the best human hearing. This is an impor tant accomplishment as it means the Uni-Q performs solidly all the way

up to the upper limit of the human ear – ensuring absolutely stunning highs and natural harmonics.

What is the lower frequency output range of the LS50W?

In standard operation, the LS50W will produce a at response to 43Hz. With our powerful on-board Digital Signal
Processer (DSP) the LS50W is capable of producing a at frequency response down to 40Hz. That means in Bass

Extension mode, you will get all but the very lowest natural musical notes without a subwoofer.

What is a “bi-amp dual-mono” amplier?

The LS50W is powered by an onboard bi-amp dual-mono amplier conguration that was designed to get the absolute
peak performance out of the 5.25” Uni-Q driver. Basically, “bi-amp” means that the high-frequencies are amplied
separately from the low-frequencies. “Dual-mono” means that each channel (left and right) have their own bi-amp
conguration. Thusly, the LS50W uses four separate amps: Two in each channel powering the high frequencies and two

in each channel powering the low frequencies.

How powerful are the amps in the LS50W?

There is one 200W Class D amplier in each channel for the low frequencies and one 30W Class AB amplier in each
channel for the high-frequencies, combined for an amazing 230 WPC. The LS50W is capable of producing 106dB of sound.

What is a Class D amp and why does the LS50W use it?

Class D ampliers are extremely efcient amps capable of producing a lot of current (i.e. power) without producing the
same heat as a Class AB amp. By using the Class D amp we were able to design an active LS50 without the need for

massive heat sinks.

Is it true that Class D amps produce a lot of distortion and noise?

The transistors in Class D ampliers switch on and off twice per musical cycle (think of one cycle as a single note) which
is why they are so efcient. The downside is that when a transistor switches off, it produces noise. Think of it as a “bounce”
as the transistor shuts down – a small amount of switching noise is introduced. However, with a properly designed Class
D amp, these unwanted signals are far above the audible range of human hearing, and with the proper use of lo-pass
lters, all of that switching noise is eradicated. That means by using a 200W Class D amp for each channel’s low frequency,

the LS50W produces a massive amount of low frequency energy without noise and without the need for giant heat sinks.