of this project is to offer a high-end kit that
even beginners in loudspeaker building can cope
with. Thus a two-way loudspeaker with
state-of-the-art drivers, a fairly simple
crossover and a cabinet that is easy to
construct. The cabinets must be rugged and well
braced, but it doesn't have to look nice to sound
The kit is built around one of the best drivers
Danish loudspeaker industry can offer, an 18H52
driver from the hands of Per Skaaning at
AudioTechnology, the company that carries the
fruit of all experiences gained by his father,
Eivind Skaaning, from participating in the
development of ScanSpeak and Dynaudio companies.
The 18H52 driver used here
is made to my specifications and is
proprietary to Jantzen Audio. Do not buy a
standard 18H52-15-06 driver from AT. It is
different with regard to materials used and voice
coil impedance and the crossover shown below
won't work properly. The 18H52's copper clad
magnet polepiece provides an almost flat
impedance profile and reduces non-linear
distortion. The chosen voice coil impedance makes
this construction well suited for valve
amplification although not for 5-10 watt SET.
25-40 watts PSE or push-pull is recommended
minimum. Obviously high-quality solid state
amplifiers may perform well too.
Please do no ask what the difference to the
standard units is, because I won't tell you (had
the question numerous times already).
Like all planar tweeters
the SWANS RT2H-A holds an extremely low moving
mass, and the large diaphragm coupled to a well
constructed die cast waveguide, makes excellent
horizontal dispersion. Like all planars, vertical
dispersion is limited and tilting the speaker a
little leaves a comfortable listening window. The
end result is speed, resolution and dynamic
integrity that leaves conventional soft domes
behind. Listening to cymbals and other
instruments with high frequency content, makes
you wonder whether you have ever heard something
similarly natural from conventional domes.
Hand clapping (applause) from an audience on live
recordings is a powerful tool for evaluating
driver integration and treble quality, and this
speaker excels over any other speaker I have
made, and based on experience I know this is
mostly due to the planar tweeter.
The RT2H-A planar tweeter
used here is a standard unit, but it has
been slightly modified (changing of damping
materials behind diaphragm), the drivers are
paired to +/- 1 dB SPL from 3-10 kHz and all
units are tested in the final AT-SW speakers
before release. I hope this will overcome the
common sceptisism toward Chinese produced
products. The diaphragm, by the way, is produced
The basic characteristic
of this construction is transparency above all
and a surprisingly powerful bass considering the
size of the bass driver. A seamless integration
of drivers provides enhanced insight into the
music and the bass reaching down to 40 Hz
delivers a solid foundation for any source
material. The AT-SW kit provides sensitivity of
86-87 dB/2.8 volts/1meter. Cabinet dimensions are
250 x 450 x 325 mm (W x H x D) if you want to
build your own cabinets. US builders may use
PartsExpress #302-730 cabinet, e.g. piano black
finish as used for the prototypes here.
I do not suggest anything other than the very
best capacitors for this speaker, thus Superior
Z-caps used in this construction.
I have run these speakers with different
amplifiers, from class B solid state to NFB
single ended triodes and feel sure that AT-SW
will deliver more and more the better the
amplifier and associated equipment. The best
sound I had was from my 5687 line stage and
modified Audio Mirror mono-blocks, but 20 watts
is on the low side unless you never play at
significant sound levels.
Further information on cost,
shipping and payment at firstname.lastname@example.org
Prototype cabs. Click image to view large.
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L2011 and L1041: Jantzen Audio wax coils. L2031: Jantzen
Audio baked air-cored coil.
All caps: Superior Z-caps. Resistors: 10 watt MOX.
crossover layout and pics.
COMPLETE KIT INCL DRIVERS
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Crossover kit incl. AT 18H52 and paired RT2H-A
drivers available from -
Jantzen Audio: email@example.com
Damping materials available (egg crate foam and
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Use a port of 60 x 150 mm (D x L) or 65 x 175 mm or 70 x
205 mm to render a port tuning of ~38Hz.
Prototype made from PartsExpress
#302-730 cabinet, black piano lacquer.
Routing for the vent.
Remember chamfering driver hole.
The RT2H-A tweeter doesn't need rebating. It might look
nice, but having shart corners it's not easy to do.
Cabinet damping is very
important for obtaining the best results,
although different materials can be used. The
prototype test cabs were damped with 30 mm egg
crate foam on all sides plus a folded layer of
acoustilux/MDM3 on top of the crossover - behind
Whether bitumen pads should be
used on internal panels is up to the overall
rigidity of the cabinet. If well braced, bitumen
pads may be omitted. Please note that bitumen
pads does not reduce sound reflections, it damps
vibration of cabinet panels. I have seen some
confusion over this.
Alternatively 10-12 mm felt pads
may be placed on all in internal panels followed
by acoustilux/MDM3 as suggested on drawing. In
addition to this, a folded layer on top of the
crossover placed behind the AT driver.
Left: Tweeter section placed in side wall toward rear
Right: Bass section placed on side wall towards rear
panel. Remove port when inserting bass section crossover.
Silver plated cobber wire in teflon sleve
Terminals to crossover boards: 2 x 25 cm black, 1 x 20 cm
red, 1 x 30 cm black.
Crossover boards to drivers: 2 x 50 cm black, 2 x 50 cm
5 meters of each delivered with kit.
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Setting up the speakers
of speakers is something I usually leave to the
builder to decide, but a few comments here on my
own experience on setting up the AT-SW speakers.
Setting up a 2-way speaker is in many ways
trickier than most 3-ways, where the bass driver
usually finds its place some 35-45 cm above floor
level. This often provides a suitable room gain
allowing a bass driver to gain a little extra
weight in the lower octaves. For a 2-way we can't
have the floor augmenting bass level as early
floor reflections would compromise the midrange.
Thus, a pair of stands is a must for the AT-SW
speakers - as for any other 2-way in this
Before making the final stands, make a pair of
mockup stands from some MDF leftovers. Make them
approx. 50 cm high, allowing additional height to
be gained from adding books or whatever below the
speakers or stands. Move the speakers around in
your listening room and try to avoid having the
same distance to floor and rear wall - not to
forget side walls!
In my listening room I always have speakers on
the long side allowing some 160-180 cm to side
walls. This may a bit of a luxury, but it solves
a lot of problems. The worst placement we can
have is the exact same distance to all three
nearby boundaries. If we place the AT-SW midbase
driver e.g. 65 cm to floor, rear and side walls,
we will have some 4-5 dB extra at 50 Hz - but a
10-11 dB dip at 160 Hz and it sounds awful.
Next to building your speakers properly,
placement is second most important thing to
consider. The sound from any good speaker can be
totally ruined by misplacement.
tilting your speakers while sitting in your
favourite listening chair. The tilt will depend
on your height, your chair and the distance to
find the best sound from the AT-SW by toeing in
the speakers to listen almost on-axis while still
being able to see inner side panels from my
you want to thoroughly evaluate the many hours
going into your project, move the whole set to
another room and hear what happens. Next, try
various amplifiers and source material, CDs and
vinyl set-up if available. I've recently compared
the AT-SW driven from an "average"
power amp (Rotel) and a 2 x 80 watts class A
solid state amp (Jungson) and the test was
devastating for the Rotel. Feel sure the AT-SW
will deliver the details from the very best
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Left: SPL @ 1 meter, 2.8 volts for drivers.
Right: Impedance and phase of drivers mounted in cabinet.
Left: SPL for 2.8 volts/1 meter for final
crossover. Right: Horizontal dispersion at 0, 5, 10 20
and 30 deg. (red, blue, green, purple).
Left: Vertical dispersion starting at tweeter
height (mid). Red = 0 deg., blue = + 5 deg., green = -5
deg., purple = -10 deg.
Right: Cumulative spectral decay from finished speaker.
Left: Final system impedance. Minimum 5 ohms at 500 Hz.
Right: SPL of drivers driven from crossover and summed
Point of crossover = 3 kHz.
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Basically it doesn't make much
sense trying to describe the sound of a
loudspeaker. What I hear is not what you or anyone else
will hear. The way we perceive sound varies enormously
and every well constructed loudspeaker may have something
to offer that will please the ear - for some people.
"The best loudspeaker in the world" is quite
often read in loudspeaker ads. Obviously this is
nonsense. The people who build it may think so, but other
people may disagree. In the end it's a matter of taste.
What is immediately apparent
once you sit in front of the ATR is the lack of
distortion, the smooth electrostatic treble and the
surprisingly deep bass considering the size of midbass
and cabinet volume. Despite the modest cabinet, this
driver goes all the way down to 40 Hz, significantly
adding to the perceived scale of the acoustic scenario.
If you think polypropylene drivers
may not be able to provide the same level of transparency
compared to magnesium or ceramic drivers, try this AT
midbass. The old ScanSpeak 18W/8543 driver was probably
the best polyprop driver in the world in the early
Nineties, but from personal experience this new AT driver
is simply a lot better. The mineral filled polypropylene
material used in AT drivers easily outperforms the old
and softer ancestors. Where hard-cones need careful
filtering to eliminate break-up nodes in the upper
registers, we can get away with simple low-order
filtering from this AT driver.
The treble quality from
this construction is where this speaker most noticeable
differ from most other brands. If you know the sound of
electrostatic loudspeakers, this is where you should seek
brands for comparison, because "electrostatic"
is what it is, and dispersion - although not as good as
the best domes - is much better compared to what is
usually experienced from fullrange electrostatics.
Magnesium drivers will
sound like magnesium drivers; ceramic drivers will sound
like ceramic drivers and polyprop drivers will sound like
- - polyprop drivers. Don't be mistaken here. Whatever
material is used for speaker cones, they will all have
their own distinctive way of reproducing sound.
Hard-cones may sound slightly "clean and
sterile" (Read: I miss the colouration of my old
paper cones) and polyprop usually have been characterised
by having a smoother and more forgiving sound (Read: It
allows me to hear all my old and poorly recorded
records). Due to the exceptional build quality of the AT
midbass combined with the electrostatic quality of the
planar tweeter, I think an exceptional good compromise is
at hand. We can't have it all, but we can choose
carefully to combine some of the best qualities of all
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AT-SW crossover is devided into two sections to
fit into PE cabs, if necessary.
Using wax coils and Superior Z-caps means a bulky
crossover and putting it all
on one board wasn't possible.
Bass section. Board = 11 x 24 cm.
Tweeter section. Board = 11 x 13 cm.
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