Manual
page 6
page 7
The Electronics
With an acoustically optimised response as a starting point, we applied DSP equalisation
to atten the response of woofer and tweeter. Thanks to the cabinet design only a few
minimum phase IIR corrections with low Q were necessary to linearize amplitude- and
phase response. Correction and cross-over were adjusted by hand, based on a multitude
of measurements in an anechoic environment. Driver errors need to be treated differently
from cabinet diffractions and automatic algorithms are unable to distinguish between the
two kinds. Finally, the acoustic sum was phase corrected to minimum phase which avoids
the pre-echos introduced by more common linear phase corrections. Measurements of the
step response conrm the effectivity of this strategy.
When adding the LS1s subwoofer an LS1 turns into a true three-way system. The DSP
again takes care of all ltering, including the cross-over and its phase correction which
has dramatic impact at low frequencies. A three-way system has never sounded so even
as this. Just like with the two-way system our DSP correction offers a freely congurable
low cut frequency. Usually the two-way is cut off at 40 Hz and the three way at 20 Hz.
Digital input signals are re-clocked by a state of the art ASRC circuit which is based on the
same oscillator as the legendary Grimm CC1 clock. Analog inputs are rst converted to
digital with a high performance A/D converter. The signal then enters the DSP, which has
a data path of 48 bits wide with a 76-bit accumulator. Each driver then has its own high
quality D/A-converter. The output of the D/A converters is directly fed into 120 W Hypex
Ncore power ampliers. The optional LS1s subs have an additional 400 W amp each.
Hypex Ncore power ampliers have the lowest harmonic distortion on the market and
are the perfect choice for the LS1 due to their linearity and excellent transient response.
Throughout the whole circuit, careful attention has been paid to component selection like
capacitors and resistors. Critical parts such as power supply regulators are of our own
discrete design. Once our circuits measure well, we start listening to tweak the last parts
by ear.
And this explains why the LS1 is not only neutral and precise but also a joy to listen to
and musically pleasing. We started with smart concepts and measurements but we did
not stop there. We listened. And doing so we developed a loudspeaker system that is
equally at home in a studio as well as in a living room. The LS1 is a true step forward into
the 21st century.
The Acoustics
The theory behind the LS1's acoustical design originates back to the 1930s and '40s.
Cabinets in those days were at but wide, which moved the so called ’bafe-step‘
frequency to lower than 250 Hz. Below the bafe step frequency, sound is radiated
equally in all directions. Above the bafe step the sound becomes more forward directed,
thereby attenuating reections against the wall behind the speaker and the side walls.
These reections normally cause phase errors in the perceived sound. Psycho acoustics
says that the ear is sensitive to phase errors down to approximately 250 Hz. The wide
bafe helps to attenuate interfering reections throughout this whole range.
Progress since the 40's has learned that edge diffraction of the cabinet deteriorates the
stereo image, hence the sides of the LS1 cabinet are strongly rounded by the legs. As
a bonus, the shallow cabinet moves the resonance along the depth axis inside the box
signicantly above the cross-over frequency of the low frequency driver. This helps to
avoid boxiness.
Next step in the design phase was the driver selection. We settled on an outstanding pair
of Seas units. The tweeter’s exceptionally low distortion in the mid range allows a fairly
low cross-over frequency that benets vertical dispersion. Its small constant directivity
horn ensures an even spread of high frequency sound.
Even dispersion is also helped by the lack of cone breakup effects in the magnesium
woofer below the crossover frequency. The woofer's long excursion permits generous
sound pressure capability down to 40Hz for the two way conguration. Adding the LS1s
subwoofer takes performance up a notch by extending the response down to 20 Hz and
further increasing attainable loudness.