Doing
the CNO speakers has been a lot of fun
and the obvious thing to do next was a 2½-way
based on the same drivers, thus the CNO-25.
Benefits from doing so is increased sensitivity,
which, based on simulation, will be around 90
dB/1 meter/2.8 volts. Next we get better power
handling and reduced midrange distortion at
higher sound levels. Two W18NX001 drivers will
make 250 cm^2 total radiating area superceding an
8" driver.
I won't be doing another
round of nextel coated driver praisel.
This can be found in other constructions using
these drivers: CNO
mkII, CNO-T25, Acapella
NEXT, Cyclop, Scoperta and SEAS-5INCH.
Setting up the CNO-25 after
having finished the crossover revealed a fully
grown-up CNO. Sensitivity is increased by 4-5
decibels and the overall bottom end weight is
significantly enhanced. Comparatively it goes
louder with less distortion due to doubling the
amount of bass drivers. Upper mid and treble is
the same as for the CNO and this was what I
wanted: Maintain CNO qualities, but increase
power handling and bottom end capability.
Enough talking, let's
go to the details.
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The Cabinet
Tilt cabinet 5 deg. Ports for 42 Hz
tuning, 36 liter net volume:
60 (ID) x 62 mm, 65 (ID) x 75 mm, 68 (ID) x 84 mm, 70
(ID) x 90 mm, 75 (ID) x 110 mm
Workshop images during crossover
fine-tuning.
Crossover version
2
CNO-25
crossover is combination of a series crossover for upper
bass and treble added a parallel filter for lower bass.
For T29CF001, increase R2
to 1R5 or 1R8, try out
both to suit your taste.
Crossover
components
Complete
crossover kit incl all above +/- drivers is available
from Jantzen Audio: contact@jantzen-audio.com
Please
note that an RC circuit can have any orientation. RC or CR, it does the same thing.
The same goes for LCR circuits, although not present
here. It can be LCR, CLR, RLC, etc.
Measurements
 
Left:
SPL 1 meter/ 2.8 volts. Overall sensitivity around 90-91
dB.
Right: System impdance = 3 ohms minimum, the price to pay
for going 2½-way. No problem for solid state amps or
25-35 watt valve amps.
Even my 8 watt 300B SET amp can run these speakers at
normal listening level,
which tells we can never fully predict how difficult a
load a speaker will be without actually trying.
 
Left: Horizontal dispersion. Read =
on-axis. Blue = 10 deg. Green = 20 deg. Purple = 30 deg.
Right: Vertical dispersion at 1 meter: Red = 10 cm above
tweeter height. Blue = at tweeter height. Green = upper
midbass height.
Yellow = between bass drivers. Purple = lower bass
height.
Overall this speaker display an even power response,
ensuring stable soundstage over a wide listening area.
 
Left:
CSD, 20 dB. Right. Inverted tweeter polarity. Point of
crossover = 3300 Hz.
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