User manual | Alpine PDX 1.1000 subwoofer amplifier Test report

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Alpine POX-1.1000
Text and Photos by
Dave MacKinnon (osmlabs.com)
he scene is Las Vegas, NV and the
T 2006 Consumer Electronics show.
With my meetings and work behind
me, it was time to cruise the show floor and see
what was going on in terms of new products. |
of course had to make a stop at the Alpine booth
to check out their insane Sinister 6 car. Once |
had finished my tour of the highly modified BMW
6-series, | checked out the other new offerings
from the Alpine crew. | noticed the company had
licensed several technologies to sell under the Al-
pine name; one was the Tympany LAT subwoofer,
the other was the ICEpower technology from Bang
& Olufsen — cool on both counts. For this review
| have the Alpine PDX-1.1000 1,000W subwoofer
amplifier, a product that utilizes the latter.
IL PINE
pg Bo
DESIGN
This amp is small — extremely small. | would go
as far as to say that it may be one of the smallest
1,000W amplifiers | have ever seen. How small is
it? The amp measures a microscopic 10-1/8 by
7-9/16 x 2-7/16 inches. This is half the size of
most competing products. The amp also looks re-
ally cool — it reminds me of a black Apple iPod, but
unlike the last amplifier product | reviewed that
looked like an Apple clone, this amp should ac-
tually sound good! Alpine has taken into consid-
eration how people install products in their cars
and made these amps stackable. The PDX (Power
Density) line features this 1,000W monoblock, a
4 x 150W four channel and a 2 x 150W unit. You
can bolt these together one on top of another and
they'll work great.
N
The chassis of the amp is also its main heat-
sink. The power supply switching devices are
attached to the bottom of the circuit board and
don't have the commonly seen plastic case — just
the raw metal junction box sandwiched to the
heatsink. Along the other end of the amp are In-
ternational Rectifier IRFB4227 Power MOSFETs.
These MOSFETs are designed for extremely high
switching speeds and low current consumption
requirements. Each of the eight devices is rated
to handle 65A of current and 190W of energy at
100°C. This, and the proprietary ICEpower driver
ICs are the key to the claimed efficiency of this
amp — more on that shortly. The battery connec-
tion to the amp sends power to a pair of 2,200pF,
25V, 105°C caps and then to an inductor before
heading to the naked power supply switching de-
vices. A pair of ferrite core transformers handle
the conversion up to higher voltage levels before
being rectified then filtered by four 1,000pF, 100V,
85°C caps. There are two additional sets of induc-
tor and filter circuits to smooth the output of the
digital switching output stage. The circuit board
is populated by mostly surface mount compo-
nents, including many of the ICs. The design and
construction is rock solid and quality from stem
to stern.
The amp incorporates a daughter board to
handle the signal processing and input stage. This
board — attached to what is actually the bottom
of the amp — is where the input and output RCAs
and the gain and filtering circuits are mounted.
Again, the board houses mostly high-quality, sur-
face-mount components.
In terms of audio features, the PDX-1.1000 is
simple but effective. The gain control is specified
as being adjustable from 0.1V to 8V. There is a
range switch beside the gain control to select
between 0.1 to 1V or 1V to 8V. Most decks will
require the amp to be set right around the 1V
mark. The electronic -24dB/Octave crossover is
adjustable from 50Hz to 200Hz. A three-position
switch controls the function of the subsonic filter.
It can be bypassed or set to 15Hz or 30Hz — the
latter is perfect to use with vented enclosures. All
these controls are mounted along the front edge
of the amplifier behind a removable black panel.
This means people aren’t going to mess with your
settings and the amp always looks neat and tidy.
On the other side of the amp are the power,
speaker and signal connections. The power block
has the set screws set at a 45 degree angle and
the wire exits downwards at the same angle for a
neat, tidy and compact look. Four 20A automotive
style fuses provide protection for the amp. There
is a set of RCA inputs and a set of outputs. Finally,
the speaker connections are made via removable
plugs. The plugs are labeled for polarity — but
their unique design allows them to be plugged in
anyway without fear of reversing polarity. From a
system tuning standpoint this is a great feature.
As | mentioned, Alpine has licensed the tech-
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nology at the heart of this amplifier from well
respected and artsy home audio company Bang
& Olufsen. The PDX-1.1000 is essentially a Class
D amplifier. That is to say the output devices are
modulated completely on and then completely
off rather than operating in their highly resistive
linear region. Without going deep into the math
and physics of why ICEpower is better than many
conventional Class D amps I'll summarize some
of the key points. ICEpower samples the incom-
ing signal at a resolution of 24 bits at 96kHz with
4x oversampling for error correction. Advanced
noise shaping circuitry allows the output devices
to operate (switch) at achievable frequencies and
still resolve the detail and nuances of the original
recording. This is done via the use of a feedback
circuit in the Noise Shaping section of the amp.
Third, the output of the switching devices is sent
through what B&O refers to as the PEDEC con-
trol system. PEDEC refers to Pulse Edge Detec-
tion Error Correction — it essentially compares
the unfiltered output of the driver stage to the
original digitized signal and provides a constantly
updated timing error correction signal. The entire
description of the circuit operation and math in-
volved is very complex, but the net result is bet-
ter control over the output device modulation for
better accuracy.
ON THE BENCH
So, how did all this math work out for the Alpine
PDX-1.1000? | set the amp up on my test bench
and connected it to my bank of load resistors to
make my measurements. Up first was frequency
response. With the crossover set at its highest
frequency (200Hz) and the subsonic filter deac-
tivated, | measured the -1dB frequency response
to be 4.06Hz to 164Hz. The -3dB frequency re-
sponse was 1.32Hz to 201Hz. This is quite narrow
on the top end, but more than sufficient for most
well designed automotive subwoofer systems.
The low frequency extension was very good. As
you can see from the attached graph, there was
some slight emphasis on the top end. But again,
given the narrow bandwidth and intended use of
5dB/dv Top 32dBY
Start: 1Hz Stop 10kHz
the amp, this won't be an issue.
| followed with a damping factor measurement
of 153.8. This is very good for a digital switch-
ing amp. | analyzed the amplifier's behavior when
It was fed a square wave in hopes to evaluate
its slew rate, but the very low upper operating
frequency prohibited any meaningful measure-
ment. Finally, | took a slew of power production
measurements. The amp produced significant
power, always more than its rated 1,000WRMS
(CEA-2006 compliant) spec; 1,082.4W at 4 Ohms
and 1,095.1W at 2 Ohms. What was truly impres-
sive was that the amp was 88% efficient while
producing this power. | measured efficiency at
1/3 power (300W) at 81%. This is quite excellent
indeed. This awesome efficiency is what has al-
lowed Alpine to mount the amp in such a small
heat sink. It also means less load on your alterna-
tor and battery. From my recollection, this may be
the most efficient amplifier | have ever tested.
CONCLUSION
The PDX-1.1000 and its brethren make a bold
statement in terms of a step forward for ampli-
fier technology and design. The efficiency is stun-
ning and an issue that every car audio enthusiast
needs to sit up and pay attention to. The cool styl-
ing, compact chassis and industry-leading tech-
nology make this amp one well worth auditioning
the next time you are in the market to provide
some slam to your subwoofers. By the way, to you
SPL fanatics out there who are limited to one bat-
tery in their respective competition class — you,
of all people, need to check out the PDX-1.1000:
nearly 1,100W while drawing around 90A of cur-
rent is truly awesome. Pas