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in my truck.
The acoustic
match greatly
improved and
now we had a
great-sounding sub-
woofer (what I won’t do for
CA&E magazine, jeez!).
To power the Stroker Pro 15, I installed a Zapco
C2K-9.0XD amplifier to run it. The 9.0XD features a
24dB-per-octave crossover. With the 1-ohm
impedance of the driver, this Zapco will deliver
2,000 watts of power. The front half of my reference
speaker system consists of a pair of USD Audio B-
72Pro WaveGuide separates. I power these with a
Zapco C2K-6.0X amplifier at 150 watts per chan-
nel. The built-in highpass crossover filter was used
to block the bass to the component system. These
amps are fed via Zapco’s Symbilink balanced line
driver SLB-U. There are no other signal processors
in the signal path.
LISTENING
After four hours of break-in time I inserted a
favorite track—Tracy Chapman’s “Heaven’s Here
on Earth.” This subwoofer goes from very low fre-
quencies all the way up the scale smoothly without
drawing attention to itself. The bass imaging was
extremely good. The bass line always stayed up
front and did not pull to the rear of the vehicle at any
point. The bass drum was tight and the bass guitar
smooth and proper. That’s what’s so intriguing
about the Stroker Pro. There is nothing faint about
the looks of this subwoofer, indicating that it could
not be anything less than a brute, yet it had an artic-
ulate and delicate reproduction quality when the
music called for it. And, it had no trouble replicating
layered bass lines. Overall, each instrument stayed
well defined and taut.
On Diana Krall’s
Love Scenes album, the stand-
up bass note changes were clear and well defined.
The note-to-note levels were equal and at no time
were they out of proportion to each other. The bass
plucks were very punchy and taut. This subwoofer
is no one-note wonder. It accurately reproduces the
frequency changes up and down the scale from the
string bass to the guitar and the drum kit. It was
very snappy and tight with excellent control. The
Pro 15 exhibited no blooming in the upper bass fre-
quencies like many of the other subs I have tested.
A great benefit to using a large diameter sub-
woofer like this one is how well it energizes the inte-
rior of your vehicle at really, really low frequencies.
Case in point, I had to remove my garage door
opener and sunglasses fr
om their usual perch over-
head at far lower volume levels because they were
rattling almost instantly.
I played the 10,000 Maniacs remake of “Peace
Train” next. It opened with a bass drum kick that
was very low in frequency. Many subwoofers will do
an adequate job on this passage, but the Stroker
Pro 15 really got the job done. Each kick of the bass
drum was sharp, solid and deep. This track illus-
trated the performance gains that large format sub-
woofers have over smaller subwoofers.
Wrapping up, I put in Usher’s latest album and
cranked up the “Intro” track that leads into the track
“Yeah!” “Intro” uses mostly acoustic instruments
with super dynamics and at 0:23 secs into it, the
Stroker punched out a super tight, loud bass line
that was still very realistic sounding. On “Yeah!” it
simply laid down powerful, pumping bass that went
down to the lowest bass notes clearly. Even on this
repeating boomfest, the bass image stayed up
front, solid and fixed.
CONCLUSION
The more I listen to the Cerwin-Vega Stroker Pro
15, the more I like it. It is the best all-around large-
format subwoofer that I have tested by a large per-
centage. It did not matter what type of music I
played, the Stroker Pro 15 made it sound correct
and good. It does its job at all volume levels and
can handle fantastically high amounts of power.
This thing is very expensive, but its performance is
exceptional! Looks like I am going have to do some
begging to get a couple for our VW Beetle show
car. Hey, Mr. Diamond! We need to talk. —EH
SUBJECTIVE SCORE CHART
Points Cerwin-Vega
Possible Stroker Pro 15
O
verall Sound Quality 50 45
Tonal Balance 10 08
L
o
w-Fr
equency Extension 10 09
C
larity at Low Volume 10 08
Clarity at High Volume 10 09
Impact 10 09
Total Subjective Score 100 88
Ratings: 00 Poor 05 Average 10 Superior
CERWIN-VEGA
STROKER PRO 15
If you were to look at the Stroker’s motor in
conventional terms, and consider the distance
from the outside of one gap to the outside of the
other, a distance of 44mm, as one long gap and
figured Xmax based on this and the voice coil
length (remembering that Xmax is voice coil
length minus gap height and that number divided
by 2), which is 38mm for the Str
oker Pro, then
the Xmax would only be a silly 3mm. However,
when you consider the dual 12mm gap aspect of
this motor
, the Xmax number is r
eally 32mm. And
if you consider the actual Bl curve of this monster
,
it’
s really more like 36.8mm, which is the manu-
facturer’s Xmax specification for this woofer.
There are a number of positive aspects to this
dual-gap technology, the biggest being the enor-
mous excursion potential. For a given coil length,
the dual gap motor will have 2.5 times more
Xmax than a conventional single gap motor. For
example, a 38mm voice-coil length with a single
12mm gap would have an Xmax of 14mm, com
-
pared to the 32mm of the Cerwin-Vega dual-gap
woofer. The other benefit has to do with how
constant Bl is at high SPL levels. Many conven-
tional woofers have a more or less “bell” shaped
Bl curve, which means that as they start operat-
ing at maximum SPL levels, the Bl or motor drive
level will begin decreasing rapidly. This coupled
with the elevated voice coil temperatures mean
that the ef
fective box Q and F3 numbers are gen-
erally higher than at low SPL levels. Effectively,
this suggests that the really low bass tends to go
away somewhat when you get extr
emely loud
with most subs. W
ith the Str
oker Pro, the Bl
curve is very flat and extended and the r
esult is
that the motor does not exhibit as much box Q
and F3 shift as is normally experienced at high
SPL levels. While this extra high output stability
is primarily due to the flat Bl characteristics of the
Stroker Pro, some of this stability can be attrib-
uted to its excellent thermal cooling characteris-
tics.
SPL in car measurement at 2.83 volts, 1 meter – with
Bruel & Kjaer
T
ype 2231 Level Meter set to Un-weighted,
SPL and Fast.
20Hz > 90.6dB
40Hz > 93.4dB
80Hz >
94.6dB
Max SPL > 136.3dB
The Max SPL measurement was taken using only 2,000
watts.At 5,000 watts,a gain of 3-5dB is conceivable.
XMAX AND DUAL-GAP TECHNOLOGY
Posted with permission from the September 2005 issue of Car Audio and Electronics ® www.caraudiomag.com. Copyright 2005, PRIMEDIAInc. All rights reserved.
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