crossover fine-tuning (picture above to
the left) I connected the 2 x 6 watts single
ended MAE amp. The
impedance of this speaker construction is fairly
flat from upper bass to the top octave. However,
at 150 Hz we have a negative phase shift due to
the vented cabinet and impedance reaches it
lowest level at 3.8 ohms. Despite ~90 dB/2.8V
system sensitivity, I hadn't any expectation of
this speaker being run from 6 watt single ended.
Let me immediately say the MAE is not the ideal
amp for this speaker, but I was surprised how
loud it could play the Acapella NEXT. Louder than
my wife would do when she plays her CDs.
Hmm... as discussed before, you have to try any
combination of speakers and amps before deciding
what goes and what doesn't.
My Autumn sale
was a goodbye to my Acapella SEas speakers.
Drivers, crossovers, vents, terminals, damping
material, wires, everything but the cabs. You
don't ship these cabs to Portugal unless you make
huge crates with loads of absorbent material. So,
the cabs stayed and having the W18 and T29
drivers the only thing left to do was ordering
the W22 bass units - and see if a fairly high
efficient Acapella could be made. The W22 comes
with a huge 134 mm magnet and promises 90 dB
sensitivity. Not bad at all. Maybe the W18 could
even be run without any attenuation.... So, the
Acapella NEXT was born.
My visitors have been quite
taken by the initial Acapella NEXT set-up. The
airiness of the midrange (lack of box
colouration), the excellent mid-tweeter
integration, the dynamic properties due to
relatively high sensitivity. And they were
surprised when I connected the 6 wpc SET MAE amp.
The treble is a little laid-back when driven from
the MAE (4R7 to tweeter), where my 20 wpc SET
Audio Mirror mono-blocks have no trouble driving
this speaker to considerable levels. The best
Acapella yet? Yes and no. If you can live with
the slightly reduced low end extension compared
to the Acapella SEas, then yes.
I like these nextel coated
drivers. They can be driven hard without
noticeable distortion. They appear surprisingly
un-coloured although not as "clean" as
the magnesium drivers. But what we're in for here
is some 5 dB rise in sensitivity compared to the
magnesium version of this construction. The
Acapella SEas is tuned to some 84-85 dB
sensitivity, so we should have an almost 4 times
more sensitive speaker.
Those who have followed recent writing on these
pages will have noticed quite some lines on the
relation between system sensitivity, size
and bass extension.
The system described here is tuned around 90
dB/2.8 volts. The magnesium W22 has a heavier
cone, lower Fs and smaller magnet compared to the
nextel W22, thus lower bass extension from the
same cabinet volume. View graph below. Despite
some 5 Hz lower F3 from the magnesium version, I
don't miss bass information, nor bass level from
the current construction.
The T29CF001 is a
magnificent tweeter. The Sonomex cone
material appears to be a good compromise between
hard domes and soft domes. The Sonomex is
significantly more rigid compared to classic silk
domes and the frequency response should reach up
to 30 kHz according to SEAS measurements. My CLIO
system only goes to 22 kHz.
Initial LspCAD modelling suggested
a very easy crossover compared to the difficult
magnesium drivers. 2nd order to bass and mid and
a 3rd order to the tweeter should be all needed
and so it stayed after crossover fine-tuning. The
roll-off of the W22 driver is an example to
follow. My measurement of the raw W22 driver was
spot on compared to the SEAS specs. Always nice
to be able to reproduce measurements. View
graphics at end of measurement section.
TS data and box
data for W22NY001
Click image for large view.
Comparing bas extension from W22EX001 and W22NY001 from
same cabinet volume.
Ports for 36-38 Hz tuning:
60 x 90 mm, or 65 x 110 mm, or 68
x 120 mm, or 72 x 140 mm
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rationale behind the three 10W 6.8 ohm resistors in
parallel is to
keep the resistors providing mid attenuation absolutely
cool. Maybe overkill, but it's cheap.
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Acapella NEXT kit with
all drivers and v1 crossover components from: http://jantzen-audio.com/
Version 1: all Cross Cap
Version 2: Superior Z-cap for mid and tweeter
Version 3: Superior Z-caps for tweeter only.
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Left: SPL @ 2.8V from all
drivers mounted in cabinet. Bass driver response
merged with nearfield measurement at 300 Hz. Red
= bass driver. Please notice an example to follow
for the bass driver. Extended response up to 5
kHz followed by a smooth roll-off. (- sorry for
merging the mid response too! Disregard blue
below 300 Hz)
Right: Only mid and tweeter is shown here.
Despite a minor middriver peak at 4.2 kHz an
overall manageable performance. The minor
midrange dip at 650 Hz is caused by rear-wave
cancellation due to the open baffle construction.
This is not what we hear.
Left: Green = combined
response from all drivers driven from crossover.
Purple = bass + midrange. Blue = tweeter. Red =
mid + tweeter.
Right: Point of crossover between mid and tweeter
is 3 kHz, where the bass and mid crosses over
around 350-400 Hz.
Left: System impedance.
Minimum is 3.8 ohm at 150 Hz. To make a long
story short: This is an easy speaker to drive and
my 20 wpc single ended triodes have no trouble
driving this speaker to considerable levels.
Right: SPL of system at 2.8 V, 1 meter. Bass
response merged at 350 Hz. Blue = port response.
The above two
measurements are not normalised for 1 m/2.8V.
Left: Vertical dispersion @ +/- 10 deg. Right:
Horizontal dispersion @ 0, 10, 20 and 30 deg. An
overall even response in the treble area over a
wide listening area. Above 10 kHz we see a
gradual decline in dispersion as can be expected
from a classic 1" dome. Only a 19 mm dome
like the HIQUPHON OWI can do better above 10 kHz.
Or the new SEAS 27TBCD-GB-DXT, but that's another
Out of curiosity I tried
to overlay my W22NY001 measurement with the SEAS
graph from the data sheet and I was pleased to
see a good correlation between measurements. Blue
= SEAS measurement. Red = my measurement where
the response merged with nearfield response at
300 Hz is close to actual and predicted SEAS
SEAS W22NY001 8" bass driver close-up.
I like this
speaker so much I'm going to give the
whole system an overhaul: Cabs need sanding and a
fresh oil rub and I'm going to finish the rear
grille, which has been on the shelf ever since I
built the cabs. A new port must be installed and
new binding posts as well.
I'm going to use
Jantzen Audio Superior Z-cabs for the tweeter and
possibly for the mid as well. I mean: The drivers
alone are some 1,000 EUR, so they deserve the
best in terms of crossover components. First I'll
try Cross Caps for the mid on one speaker and
Superior Z-caps for the mid on the other and try
an AB test.
The crossover layout
has to be prepared to 3 x 22 uF Superior Z-caps;
takes quite some space, 123 x 106 mm. The bottom
panel should leave plenty of room for the mid
crossover. The bass crossover will be on the rear
panel with the coil upwards to keep distance to
mid crossover below. The tweeter crossover will
be placed right above the tweeter like the Acapella
Here are some pics from the work:
New foam has been added to the rear panel and the fillets
holding the grille has been painted black.
Tweeter X-over is placed like before, right above
2.5 mm^2 Supra mounting cable custom made for Jantzen
Audio is used throughout.
New port is installed. 68 x 120 mm.
sections for bass and tweeter shaping up.
Left: Bass crossover section. Simple 2nd order.
Right: Tweeter crossover section, 3rd order.
Connection from bass and tweeter crossovers to drivers.
Now, this is a
temporary set-up. The Superior Z-caps to
the right is going to stay in place (1 uF + 8R2
bypassing the series 0.82 mH coil. The 10 uF
Superior Z-cap goes to ground. The series 68 uF
to the left is the series input capacitor making
the high-pass filter together with the 4.5 mH +
4R7 going to ground. For my initial set-up I
by-passed the 68 uF Cross-Cap with a 1.5 uF
Superior to possibly optimise the performance of
the Cross-Cap. So far, so good.
Below to the right you
can see a chunky load of paralleled Superior
Z-caps making almost 68 uF capacitance. This is
going into the other speaker and I'm going to
AB-test these two speakers. Quite a challenge I
think. Everything is the same except for the
chunk of Superior Z-caps for the midrange in one
Disregard the black colour
of the 10 uF Superior Z-cap. This is a test
samples I had before the bordeaux red colour was
Left: Mid X-over
section seen from above. As can be seen,
a lot of space is left open for 3 x 22 uF
Superior Z-caps in parallel; black marking on
Right: Mid X-over section with series
Superior Z-caps. The bottom panel was
given a grey colour, just to look nice for the
Mid crossover layout for Superior Z-caps.
Mid X-over section ready for
Right: Bass X-over section on
rear panel with coil as far away as possible from
mid section coils.
Before fastening the
bottom panel, two sheets of MDM3 damping material
were folded and placed above mid X-over. Take
care not to block vent.
All panels in bass section are damped with 20 mm
polyester foam. Use e.g. 20-30 mm egg-crate foam.
Sonic evaluation of mid
series capacitor contest
Well, this is difficult!
Having set up the two speakers as described
above, the fun started. One speaker with Superior
Z-caps (SZC) to the mid, the
other with Cross-caps (CC). All
other things the same. Frequency response was
checked and was the same for the two speakers
within 0.5 dB. It's hard to get any closer than
that. In my workshop I have a connection panel
attached to the power amp so that I can switch
between two pairs of speakers.
The two speakers
certainly didn't sound the same. One brighter
than the other. The CC version
sounded brighter compared to the SZC,
but at the same time, while listening to the SZC
version my perception of the sound could swap -
and all of a sudden I could hear the Superior
Z-cap version being the brightest. Weird!!
The problem is this: With the CC
the sound is somewhat more compressed compared to
the SZC version. With the CC
the midrange appears to be located
around the speaker front panel plane, where the SZC
has a significant deeper soundstage, thus less
presence is perceived, yet it allows you to focus
your attention on the bright (treble) parts of
the instruments and voices and then - brighter.
Quite simple actually. The SZC
will allow you to focus on details that standard
MKPs simply cannot resolve.
During this exercise I
changed the position of the speakers from time to
time - left and right. These are dipoles or
rather semi-dipole speakers and highly dependent
on room position. However, still what is
described here followed the speakers no matter
what position they had. The SZCs
simply reveals details and a depth in the
acoustic scenario the CCs are
not capable of. The CCs
certainly aren't bad, not at all. They very much
sound like what we're used to hear from the
majority of hifi-speakers. And if you don't have
high-quality front end gear, forget about the SZC.
It may not pay off and you should start looking
elsewhere in the overall chain of components in
I once borrowed an
expensive Parasound pre-poweramp set-up.
Mega watts and I've never seen so many
transistors and integrated circuits in a preamp.
Sound? Nice, smooth - and utterly dull and
A visitor brought a mega NAD integrated. Sound?
Nice, smooth - and seriously lacking dynamics
compared to my homemade valve preamp + Rotel
RD981 workshop set-up. I was quiet surprised by
this, but that's how it was. Sorry NAD. I've
stopped reading Michael Fremer reports after his
enthusiastic review of the same NAD amp. This guy
simply can't hear anymore.
Point is: The Supreme Z-caps
may not be the only thing that will ruin your
budget, so watch out!
I better order 6 x 22 uF
SZC. Having bundled my residual stock of
Superior Z-caps I now have both running with SZCs
and they are in my livingroom right now, driven
from my 20 wpc SET amps. Thank Heaven I didn't
get rid of the Acapella cabs during my Autumns
sale. 20 wpc do well, even up to considerable
levels, but ultimately I recommend 40 wpc really
high-quality watts for these 90 dB/2.8V speakers.
It will provide a more firm bass and the ability
to play really loud too.
What more can I say?
Well, if you have some 10-15 kilo US $ burning in
your pocket for a pair of commercial speakers,
ask your carpenter what he takes for a pair of
Acapella cabs. You may save megabucks in doing
OK, OK, I know, but as one of my American
colleagues always says: "If it ain't lying,
it ain't bragging!"
- and here's the final mid
some chunky beasts!
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