was made before I started my
diy-loudspeaker website, and I never found the
time to write anything about it. The drivers here
are among my few favourites and the W15CY001
drivers were acquired for the Point75
dipole speaker and the
HIQUPHON OWI was bought only because I wanted to
own a pair of these - probably - best ever made
19 mm domes, thanks to Oscar Vroending at HIQUPHON.
The Point75s were sold
to fund the Acapella adventure and it was only
recently I bought another pair of the W15CY001
midbass drivers. A shop in Copenhagen had a
sell-out of SEAS drivers.
I had a mail from Michael Boyd expressing his
surprise of the magnificent qualities of the W15
driver, but he found the overall balance of the
construction well on the bright side - and had I
ever tried the BBC voicing of this speaker? Well,
I hadn't and looking at the old measurement I
have to admit the overall balance is very flat
and maybe voiced to be too much of a real
So, time to heat up the
soldering iron and take a second look at
this construction. The W15 and OWI were placed in
my 7.5 litre test cabs and the OWI had a lot of
Gaffa tape to cover a wider routing from other
constructions. Test cabs are still 19 x 30 cm and
driver placement is as seen on construction
Crossover for the W15/OWI
First of all I
wanted to see if the original crossover
(V1, not shown) could be modified by simple means
so that replacing expensive crossover components
could be avoided. By adding a resistor (R2021) in
series with the 6.8 uF capacitor in the low-pass
section, the 1-3 kHz range can be attenuated
1-1½ dB, having an immediate impact on the
forwardness of the sound. Tweeter obviously
needed some further attenuation, thus the 8R2
(R1011) is replaced by 10R and a 3R3 (R1061) is
added in series with the tweeter.
Overall the crossover
topology is very close to LR4 and given the
tweeter's placement some 25 mm ahead of the W15's
acoustic centre, both amplitude and phase fall
nicely into place. Using LR2 would require 20-25
mm recession of tweeter (stepped baffle) and the
Hiquphon is not easy modelling for this setup.
The W15/OWI Speaker Kit
Complete kit excl tweeter available from Jantzen Audio.
HIQUPHON OWI is available here
2 x 4.7 uF caps in tweeter section may be replaced by
Order 4 x 4.7 Superior Z-caps. Pay notice to size of Z-caps in
Supra cable may be replaced by silver plated cobber in teflon.
Order 1.5 meters of both black and red wire.
Suggested crossover layout
Left: The treble level is
now 1-2 dB below midrange level and provides a
more natural balance. The response here is merged
at 350 Hz with a nearfield measurement of bass
driver and don't pay too much attention to the
level below this point. Nearfield measurements do
not tell the true level of bass at 1-2 metres
distance, but it does tell where the bass driver
starts rolling off.
Right: You may think that adding
3R3 in front of the tweeter changes the point of
crossover and mostly it does, but here it goes
well and the phase-tracking between drivers are
kept in good shape. Reversing the tweeter
polarity produces a deep suck-out at 3 kHz.
Left: For those
interested, here are the response profiles of the
drivers without crossover attached. The W15 is a
doing fine and the cone break-up starts above 5
kHz. Excellent for a 5" magnesium cone
Right: Significance of
notch-filter to reduce peaks around 8kHz.
Significance of mid notch filter.
Right: The most critical part of the crossover is the
0.30 mH coil in the 8 kHz notch-filter.
This really has to be 0.30 mH. Red = 0.30 mH, green =
0.33 mH and blue = 0.27 mH.
of speaker construction. A reasonably easy load on the
~7.6 litres cabinet.
The Jantzen kit comes with a 35 mm x 120
mm tube. Used as-is, this will make a vent tuning of 53
I suggest using the 35 mm vent at 120 mm length if
speaker is placed near to the front wall.
If placed free on a stand, I suggest a slightly higher
tuning. Cut 35 mm vent to 90 mm length.
View builders of the W15/OWI Kit
built by Joffrey, NL
W15/OWI, built by
W15/OWI, built by
John Eekels/Holland, exquisite veneering