Page 1 ongratulations on your fine judgement. In its class the DALI

Page 1 ongratulations on your fine judgement. In its class the DALI
 ongratulations on your fine judgement.
In its class the DALI 15a is one of the
very finest loudspeakers on the market.
To get the maximum performance from
DALI 15a we recommend that you read this
manual before installing your new speakers.
POSITIONING
SIGNAL SOURCES
CONNECTION
PHASING
DAILY USE
DOCUMENTATION
MEASUREMENTS
SPECIFICATIONS
IT | | O3 | SA | St | SIND
Please note that DALI 15a
is provided in mirror-imaged
pairs. The right speaker has
ALI 15a gives the best oblique bevelling on the left, and
sound reproduction when the left speaker has oblique
placed on a speaker stand at a bevelling on the right.
height of 30 cm (12 in). They Dali 15a should be placed
may be close to the back wall vertically.
but should not be placed at a Corner location should be
distance of less than 50 cm (20 avoided.
in) from the side walls.
Alternatively DALI 15a
may be placed on the wall or on a
bookcase.
50 cm /
20 in
30 - 60 ст /
12 - 24 т.
><
he distance from ANGLING (TO А
your normal listen- N ot normally neces-
ing position to both sary except where
speakers should be | the walls are highly
equal. This distance sound absorbent. In this
should also equal the case a slight angling
distance between both may improve stereo
speakers. В imaging.
\ A Te recommend the use of Limited sound reproduction is
the best speaker cables often caused by misadjustment
and, especially, a very good and/or weak signal equipment.
turntable or CD-player.
E pu EEE CRECER E ONCE AR ARENA LA aa ja 3 AI
he gold plated terminal on
DALI 15a makes it possible
to use banana plugs or heavy
bared wires for amplifier
connection.
IMPORTANT!
Turn off the amplifier when you
are working at loudspeaker
connection!
o get true stereo-reproduc-
tion it is necessary that the
loudspeakers are phased
correctly. Always connect the
amplifier + to the loudspeaker
+, and the amplifier — to the
loudspeaker —.
Ón most speaker cables one
of the leads will have an
indication making it easy to do
this the right way.
AMPLIFIER
‚+ — LOUDSPEAKERS = +
he main point here is: enjoy
the music! The only regular
maintenance required is occas-
sional cleaning of the surfaces.
Dust with cloth.
Brush with a clothes- brush or
vacuum clean with a brush
attachment.
he Bass System
The bass performance of DALI 15a is a result of
much experimentation to determine the optimum balance
between enclosure volume, lower cut-off frequency and ef-
ficiency. As every speaker designer knows, these three pa-
rameters are directly related and it is the correct balance
of compromises that makes for a successful design. We
wanted to keep the internal volume of DALI 15a at 29 lit-
res, thus sacrificing something in terms of either efficien-
cy or lower limit. A reference output of 115 dB at 1 metre
stipulated a cut-off frequency of 38 Hz. This reference effi-
ciency is directly comparable to DALI 7a. However, by
virtue of its greater volume, DALI 7a plays 4 Hz lower in
the bass.
A short explanation of the physics concerning bass re-
sponse is in order here. The bass capabilities of a speaker
follow a quadratic function: That is for every octave of ext-
ra bass performance, four times as much air must be mo-
ved. To achieve good efficiency with a-3 dB point of 38 Hz
requires a bass driver with special construction techniqu-
es. It must have both a very large magnet sytem and a ve-
ry long linear excursion limit. It is this design that we ha-
ve implemented for DALI 15 a, along with a thick (1 mm)
polypropylene cone and an enormous magnet assembly -
equal to that used by DALI 7a. Due to its smaller size,
however, efficiency is somewhat lower and to compensate
for this we have changed the impedance to 6 Ohms. This
has the effect of drawing more amplifier current, hence
maintaining high efficiency (for the same volume control
setting).
The system is a pure 4th order Butterworth type, tuned
in to provide flat response through the pass band.
The Midrange and Treble System
The midrange driver is the same 3” dome unit employed in
DALI 7a. It is fabricated from a textile compound which
is first impregnated then later surface-treated with a dam-
ped compound. The driver is mounted in a large double
chamber sub-enclosure, and the result is exceedingly neut-
ral response from 600 Hz to 4000 Hz.
With increasing frequency, dome drivers become prog-
ressively smaller acoustically with the result that the
centre stops oscillating entirely and eventually only the
voice-coil assembly moves. Hence a transition must occur
from piston action to breakup mode, and it is the quality
of the surface treatment that dictates how smooth this
will be. With correct application this can be accomplished
extremely smoothly resulting in very flat frequency re-
sponse. This critical process of coating the dome is ac-
complished by hand, requiring great skill and precision.
Since we make such stringent demands on this process,
we are assured of receiving the best of the production. Ac-
cordingly we must pay more, but the extra quality more
than compensates for the additional outlay,
6
For frequencies 3000 Hz and upwards, a¥% metal dome
unit is used. This driver has been designed with equal care
and precision, The magnetic circult is built around a solid
core and bottom plate, providing less magnetic loss and
maximum flux density across the air gap. In addition it
has the extra advantage of blending particulary well with
the rest of the system.
Linear Directivity Crossover Design
Expressed simply, this concept involves smooth frequen-
cy response measured both on axis and off axis at very wi-
de angles. This very critical and largely overlooked perfor-
mance parameter tells us much about the final »room in-
terface«. The basic theory is that the frequency compositi-
on of reflected sound should not be significantly different
from what we can measure conventionally, that is at 1
metre on axis.
We stipulate that the response measured at angles of up
to -70 degrees should not be significantly different from
that measured at 0 degree. Only if this area is optimised
will real smothness and precise imaging be achieved. In
practice, linear directivity is achieved by matching the
crossover frequency directly to the driver's diameter and
employing asymmetric 40 dB/Decade (12 dB/Octave) and
60 dB/Decade (18 dB/Octave) slopes. Only the finest com-
ponents are used: heavy coils, metallised polypropylene
capacitors and LC-OFC cable.
The Enclosure
No loudspeaker is better than its enclosure. This sounds
simple, but cabinet design is as complex a science as any
other area in loudspeaker construction. It has been proved
empirically that control of enclosure resonances is crucial,
especially those with a wide low Q nature. Therefore, we
spare no effort to construct cabinets synthesising thick-
ness of walls, bracing, materials and damping.
The research into cabinet behaviour includes three di-
mensional accelerometer measurements to closely moni-
tor behaviour of resonances. In conjunction with many
hours of listening tests, these techniques have given us
the DALI 15a cabinet - one of the finest in production reg-
ardless of price. The front baffle is fabricated from 50 mm
high density fibre board, the back from 20 mm closely
pressed hardboard and the sides of 22 mm premium grade
chipboard. Veneer is used on both sides to control reso-
nances further. The massive front baffle and the stagge-
red thickness provide truly »boxless« quality to the
sound.
Dali 15a is a design based on research and understan-
ding, not guesswork and chance. And each component has
been chosen to »integrate« particulary well with the whole
system, the result is truly outstanding, a speaker which
must surely rank in the top of its class.
Frequency response on axis and
70° off axis.
Input impedance.
Cabinet type. ................... .. .. B4 bassreflex
Drivers
Woofer .............. ..... 10”, super long stroke
Midrange 1111111111 . ... 3”, dome
Tweeter ........ ............... 3/4”, metal dome
Crossover . . Linear Directivity. 1st. quality components
Crossover frequency LL LL LL 1000 Hz, 3000 Hz
Impedance. ......................... . .. 8 ohms
Systemresonance ................... ...... 36 Hz
Frequency response + 3dB ............ 38-25,000 Hz
Listening window + 2dB hor. ......... .... | 140°
Ver. .............. +9°,-7°
Sensitivity (2.8V). ............ 89 dB/Im
Recommended amplifier
powerratings ................ .. 20 to 200 W/channel
Dimensions
Height ............ 54 cm (21 1/3”)
Width. ........................_ 29.5 cm (11 2/3”)
Depth ........... 31.5 em (12 1/2”)
Net Weight ............. 15.5 kg
Specifications are subject to change without notice in the
course of product improvement.
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