You are here

Antec SmartPower 2.0 SP-450 ATX Power Supply

July 30, 2005 by Devon
Cooke
with Mike
Chin

*POSTSCRIPT added Oct. 22, 2005*

Product
Antec SmartPower 2.0 SP-450

450W ATX12V 2.0 Power Supply
Manufacturer
Antec
Market Price ~US$60

Two years ago, most ATX PSUs in the retail market featured at least
one 80mm fan. In the past year, the bottom mounted 120mm fan has become the
norm, and 80mm fans have become almost rare among higher end retail PSUs. The
Antec SmartPower 2.0 is a double anomaly because it uses two 80mm fans, one
mounted at each end. It's only one of a small handful of models that use this
this design, which has its advantages and disadvantages.

The "2.0" part of the SmartPower's name is important: The original
SmartPower line is not ATX12V 2.0 compliant, and due to the higher demand on the 12V rail, they may have difficulty powering
a current high-end system. There are three other models in the SmartPower 2.0 lineup: 350, 400 and 500. The 500 has an additional feature not found in the other models: Detachable output cables.

The SmartPower 2.0 is one of four power supply lines offered by Antec.
TruePower 2.0, NeoPower, and Phantom are Antec's high-end, modular and fanless
products, respectively. The SmartPower 2.0 is Antec's mainstream line, and is
designed to meet the needs of the majority of users. It may not be able to boast
that it is the best at anything, but there is one area where it beats all of
Antec's other models: Price. Overclockers and gamers may turn their noses up
at the SmartPower in favor of Antec's pricier models, but the SmartPower still
does what a power supply is supposed to do: Supply power.



The classy, uncluttered, full-color box
suggests an experienced retail marketing
team.

Feature Highlights of the Antec SmartPower 2.0 SP-450
(from
Antec's
web site
)
FEATURE & BRIEF COMMENT
ATX12V version 2.0 The latest major revision,
supported by most recent power supplies.
ATX12V v2.0 compliance allows
SmartPower 2.0 to consume up to 25% less power than standard power
supplies, saving you money on your electric bill
This is a claim based
on Intel's minimum and recommended efficiency.
4 SATA Connectors support Serial ATA optical drives Yes, it supports optical
drives, but you'll more likely be using them to power your hard drives.
Flow-through dual 80mm fans (one intake and one exhaust) See discussion of 80mm
vs. 120mm fans below.
Unique Dual Fans Technology: Exhaust fan starts to spin when the power
supply reaches certain temperatures
to ensure proper airflow, the
second fan spins on power up
At low levels, only the
internal "intake" fan is used, which should be good for noise
levels. We'll find out how good..
Industrial grade protection
prevents damage resulting from short circuits, power overloads, excessive
current, low voltages and excessive voltages


"Industrial grade"
doesn't really mean much, but more protection circuits are always welcome.
Low voltage protection is unusual.
Increased 12V output capability for system components that consume
more power from 12V rail
"Increased"
is relative to older power supplies based on ATX12V 1.x.
PF value greater than
90% (EU only)
It's "EU only"
because only the EU requires it.
Gold plated connector
for superior conductivity
Generally, gold plating has high conductivity and will not tarnish, but when mated with connectors with the more common nickel or tin plating, galvanic corrosion can occur over time, especially in humid environments.

OUTPUT SPECIFICATIONS

SPECIFICATIONS: Antec SmartPower 2.0 SP-450
AC Input
115 / 230VAC @ 47-63Hz
DC Output
+3.3V
+5V
+12V1
+12V2
-12V
+5VSB
Minimum Output
0.5A
0.5A
1.0A
1.0A
0.0A
0.0A
Maximum Output
32A
30A
15A
17A
0.3A
2.0A
Maximum Combined
150W
180W
180W
3.6W
10W
430W*
13.6W
443.6W*

*There was some confusion about the specifications for the SmartPower 2.0.
We managed to find three sources of specifications, each slightly different:
The web
site
, the retail box, and the label on the unit itself. The variation between the
three sources was minor; all of the actual line capacities were consistent.
However, the combined maximum output for the +3.3V, +5V and the two +12V rails
was different in each source. The web site lists the maximum as 410W, the box
lists it as 430W, and no maximum is given on the actual unit. Depending on which
source you believe, this puts the total output capacity (for all rails) at either
444W or 424W ? not quite the 450W listed in the marketing literature. For
the purposes of this review, we give Antec the benefit of the doubt and
treat the higher number as correct.



The specifications listed on the actual unit are incomplete: No maximum
capacity is listed.

TECH TIP: ABOUT "INDEPENDENT" 12V LINES

Intel's ATX12V V2.2 PSU Design Guide, the industry bible for PSU makers, states:

"In cases where expected current requirements is greater than 18A a second 12 V rail should be made available.

"The 12V rail on the 2 x 2 power connector should be a separate current limited output to meet the requirements of UL and EN 60950.

"12V1DC and 12V2DC should have separate current limit circuits to meet 240VA safety requirements."

It's important to remember that when there are two12V lines, they still draw from the same main source. It's not like there are two 120VAC:12VDC power conversion devices in a PSU, this would be way too costly and inefficient. There is only one, and the two rails draw from the same transformer. Each rail is coming from the same 12V source, but through its own "controlled gateway".

PSU makers' specs are misleading in that they rate the current capacity of each 12V rail independently. What really matters is the total 12V current: Generally, up to 20A is available on any one 12V line, assuming the total 12V current capacity is not exceeded.

An analogy that may help: Think of 12V1 and 12V2 as two identical water taps fed off short pipes joined in a Y-junction to a single larger pipe. The total amount of water flow available through the two pipes is always the same, it's dictated by the pressure behind the big pipe. Each of the two taps have a maximum potential water flow potential that is lower than the maximum available through both taps together. How much water flows through each pipe depends on how much each is open. The "position of the tap" in the PSU is dictated by the power demand of the components connected to it.

What the above means is that you don't need to worry about imbalances in power draw on the 12V lines -- as long as no single rail is asked to deliver more than 20A. PSU makers seem to mark each line for max current on a purely arbitrary basis. A PSU like the Antec Smart Power 2-450 rated for 32A max total on the 12V lines can be labelled many different ways:

12V1: 14A, 12V2: 18A

12V1: 15A, 12V2: 17A

12V1: 16A, 12V2: 16A

12V1: 17A, 12V2: 15A

12V1: 18A, 12V2: 14A

It could also be marked 19A + 13A or 20A + 12A, but being a cautious bunch, engineers will probably not specify more than 18A on any one line. This allows a 2A margin of error for the current limiting circuit. Antec's specs (and those of all dual 12V line PSUs) would be much more precise if it was appended with something like the following:

The maximum 12V current available is 32A. Over-Current Protection limits current delivery above 18A on either 12V1 or 12V2 rails. Up to 18A can be delivered on either 12V line, as long as the 32A maximum is not exceeded. OCP also limits the total DC output of the PSU to 444W.

PHYSICAL DETAILS

Compared to some of the recent power supplies we've seen, the SmartPower 2.0
is decidedly utilitarian in appearance. The casing is battleship grey, and the
only attention paid to appearance is the stamped Antec logo near the intake, which is odd, because once the unit is mounted inside the case, it will be invisible.
No matter; we care little about surface appearances.



The exterior of the case is battleship grey.



The Antec logo is stamped over the intake fan.

Apart from a small vent above cables exiting the casing, the SmartPower 2.0
is completely sealed except for the fan holes. The position of this vent is
near the intake fan where you would expect to find a dead spot in the
airflow.

Most of the air flows in via the front fan
and exits at the rear exhaust. This should create a tunnel effect that pulls
heat through the power supply and cuts down on dead spots. This is in contrast
to a power supply with a 120mm where air is forced inside and left to find its
own way out. Which approach is better depends on the exact layout of the internal
components, but the airflow does not have to execute a 90 degree turn, and the straight airflow path should make it simpler to optimize the positions of the internal components.



A small vent beside the intake fan is the only "passive" outlet
for air.

Both the intake and exhaust fans are protected by wire grills, which create
less airflow resistance than most stamped grills.



Wire grills, which are lower impedance than stamped ones, are used for both the intake and exhaust fans.

The intake and exhaust fans are not aligned with each other; instead they occupy
opposite corners so that the airflow does not bypass one side of the power supply.
The internal components are quite sparsely distributed, and there is plenty
of room for airflow. It is possible see this by looking directly through the
power supply, in one fan and out the other.

The interior of the SmartPower 2.0 is dominated by two L-shaped aluminum heatsinks
in line with the exhaust fan. The heatsinks are finned on both sides and quite
substantial. The vertical part of the heatsinks divide the power supply into
three parallel sections, each with its own airflow. Overall, the internal design seems
to be well optimized for cooling.



Plenty of free space inside that allows air to pass easily from one end
to the other.

Note offset position of fans so the airflow is forced across all of the components.



The fins of the heatsinks form channels that direct airflow (and heat) down
the length of the power supply.

The wires are neatly organized along one side of the casing, where they merge
together as they leave the power supply. These are the least heat-critical components
of the power supply, so it makes sense to place them out of the main airflow
path.



Wires are neatly organized along one side.

The intake fan is not a standard 25mm thick fan; it's only 20mm thick. This
was probably done to keep the total length of the casing down, which is a surprisingly short 6.25" ? a quarter inch shorter than the usual 6.5". It also allows
a slightly larger gap between the fan and the internal components, reducing
impedance and back pressure. The low profile fan raises a warning flag for noise,
however, as there are few fans of this thickness that we would consider quiet.

The short length is a contrast to the OCZ 470, another push-pull dual 80mm fan design PSU tested last year. The OCZ 470, a much higher priced model, measured at least an inch longer than standard ATX PSUs. Both of its fans were 80x25mm.



The intake fan is a thin 20mm thick fan.

120mm VS. 80mm FANS

120mm fans have become the norm in power supplies,
but it has not always been this way. Traditional power supplies use a single
rear-mounted 80mm fan, with a straight-through airflow path. However, the 80mm fan has
fallen out of favor, probably more because of the successful marketing of the 120mm fan PSU than any compelling technical superiority.

In free air, a 120mm fan produces far more airflow than an 80mm
fan at the same speed, so designing a power supply around
a 120mm fan seems to make sense. Another reason for using a 120mm fan in a power supply is to help exhaust heat
from around the CPU, which sits directly below the power supply in a normal
ATX case. This can be helpful, or even necessary in a conventional case,
but it is less than optimal when building a quiet system. The reason: The CPU
heat must be exhausted through the power supply, which means a higher fan speed
? and thus more noise ? is needed to cool the power supply.

In order to fit a 120mm fan into a standard ATX12V power supply, it must be
situated on the bottom. This means that the airflow from the
fan must make a 90° turn in order to leave the power supply via the rear
exhaust. The airflow impedance is increased and the
total amount of airflow correspondingly reduced. Not all of the airflow actually makes the right angle turn; some of simply bounces right back at the fan, causing significant
back pressure and turbulence, and further reducing airflow.

The size of the 120mm fan also impinges on the amount of space available for components and for the heatsinks, which has a negative impact on cooling. All other things being equal, the smaller heatsinks required to fit with a 120mm fan make it harder to dissipate the heat.

So there are some serious design considerations for a 120mm fan PSU. Even though a 120mm fan can move more
air in free space, its effectiveness inside a power supply is reduced by the
impedance and back pressure inside the power supply. In fact, a well-implemented
80mm fan PSU design may produce better cooling for key components in the PSU than a 120mm fan design.

PUSH-PULL DUAL FANS

The second fan in the SmartPower 2.0 cannot not increase the maximum
potential airflow ? this is limited by the surface area and airspeed of
the slower of the two fans ? it does increase the pressure
of the airflow. The increase in pressure still results in increased actual airflow through the unit because higher pressure can better force the air to
flow around obstacles in its path.

Another benefit of an 80mm power supply is the
location of the primary intake at the rear of the power supply. This probaby leads to
less heat in the power supply because the intake
is a bit farther away from the CPU, and most cases have an exhaust fan directly beneath the PSU to take away some of that CPU-generated heat. It is also possible to create a fresh air
intake duct between the power supply and one of the top optical bay drive bays so as to keep the PSU fan speed as low as possible.
This technique is almost impossible to pull off with a 120mm fan power
supply.

The main benefits, then, of the Smart Power 2's push-pull dual-80mm fan design are:

  • Higher pressure than single fan allows greater effective airflow through the high impedance pathway of a PSU.
  • Straight-through airflow path means less turbulence and back pressure, and improved evacuation of heat.

There are a few disadvantages to the "flow-through" design
of the SmartPower 2.0, related to the advantages:

  • The airflow around the CPU that a 120mm power supply provides must be made up
    with a system exhaust fan.
  • Extra care must be taken not to clutter the small intake area with spare
    cable sets.

CABLES AND CONNECTORS

There are a total of seven cable sets plus a fan RPM cable to provide fan speed
information to the motherboard:

  • 12" cable for main 20+4-pin ATX connector
  • 13" auxiliary 12V connector for the CPU
  • 13" cable with a 6-pin PCI-e connector
  • 24" cable with three 4-pin IDE drive connectors
  • 24" cable with two 4-pin IDE drive connectors and
    one floppy drive power connector
  • 2 x 19" cables with two SATA drive connectors each
  • 21" fan RPM monitor cable

There are enough connectors for almost any system. Four SATA connectors is very generous and there is also a 6-pin PCIe connector
for use with high powered video cards. Workstations are unsupported, as
there is no 8-pin EPS12V connector for dual CPU motherboards. A second PCIe connector
would also make SLI more convenient, although most SLI users are likely to
want more power.

The main complaint with the cables is the short length, which makes cable management
more difficult. It also makes the SmartPower 2.0 unsuitable for use in a case
where the motherboard is mounted upside down, such as the SilverStone TJ-06,
or where the power supply is not mounted in the standard position, such as the
Antec P180.

TEST RESULTS

For a fuller understanding of ATX power supplies, please read our article Power
Supply Fundamentals & Recommended Units
. Those who seek source materials
can find Intel's various PSU design guides, closely followed by PSU manufacturers,
at Form Factors.

For a complete rundown of testing equipment and procedures, please refer to
the article SPCR's Revised
PSU Testing System
. It is a close simulation of a moderate airflow mid-tower
PC optimized for low noise.

In the test rig, the ambient temperature of the PSU varies proportionately
with its output load, which is exactly the way it is in a real PC environment.
But there is the added benefit of a high power load tester which allows
incremental load testing all the way to full power for any non-industrial PC
power supply. Both fan noise and voltage are measured at various standard loads.
It is, in general, a very demanding test, as the operating ambient temperature
of the PSU often reaches >40°C at full power. This is impossible to
achieve with an open test bench setup.

Great effort has been made to devise as realistic an operating
environment for the PSU as possible, but the thermal and noise results obtained
here still cannot be considered absolute. There are far too many variables in
PCs and far too many possible combinations of components for any single test
environment to provide infallible results. And there is always the bugaboo of
sample variance. These results are akin to a resume, a few detailed photographs,
and some short sound bites of someone you've never met. You'll probably get
a reasonable overall representation of that person, but it is not quite the
same as an extended meeting in person.

REAL SYSTEM POWER NEEDS: While
our testing loads the PSU to full output (even >600W!) in order to verify
the manufacturer's claims, real desktop PCs simply do not require anywhere near
this level of power. The most pertinent range of DC output power is between
about 65W and 250W, because it is the power range where most systems will be
working most of the time. To illustrate this point, we
recently conducted system tests to measure the maximum power draw that an actual
system
can draw under worst-case conditions.
Our most powerful P4-3.2
Gaming rig drew ~180W DC from the power supply under full load ? well within
the capabilities of any modern power supply. Please follow the link provided
above to see the details. It is true that very elaborate systems with SLI could
draw as much as another 150W, but the total still remains well under 400W in
extrapolations of our real world measurements.

SPCR's high fidelity sound
recording system
was used to create MP3 sound files of this PSU. As
with the setup for recording fans, the position of the mic was 3" from the exhaust
vent at a 45° angle, outside the airflow turbulence area. The photo below shows
the setup (a different PSU is being recorded). All other noise sources in the
room were turned off while making the sound recordings.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that fan speed varies with temperature,
not output load. A power supply generates more heat as output increases, but
is not the only the only factor that affects fan speed. Ambient temperature
and case airflow have almost as much effect. Our test rig represents a challenging
thermal situation for a power supply: A large portion of the heat generated
inside the case must be exhausted through the power supply, which causes a corresponding
increase in fan speed.

When examining thermal data, the most important indicator of cooling efficiency
is the difference between intake and exhaust. Because the
heat generated in the PSU loader by the output of the PSU is always the same for a given power level, the intake temperature should
be roughly the same between different tests. The only external variable is the ambient room temperature. The
temperature of the exhaust air from the PSU is affected by several factors:

  • Intake temperature (determined by ambient temperature and power output level)
  • Efficiency of the PSU (how much heat it generates while producing the required output)
  • The effectiveness of the PSU's cooling system, which is comprised of:
    • Overall mechanical and airflow design
    • Size, shape and overall surface area of heatsinks
    • Fan(s) and fan speed control circuit

The thermal rise in the power supply is really the only indicator
we have about all of the above. This is why the intake temperature is
important: It represents the ambient temperature around the power supply itself.
Subtracting the intake temperature from the exhaust temperature gives a reasonable
gauge of the effectiveness of the power supply's cooling system. This is the
only number that is comparable between different reviews, as it is unaffected
by the ambient temperature.

On to the test results..

Ambient conditions during testing were 25°C and 20 dBA, with an
input of 120 VAC / 60 Hz measured at the AC outlet. It was a couple of degrees
warmer than usual in the lab, and the Intake Temp readings in the measured data
table below reflects this.

ANTEC SMARTPOWER 2.0 SP-450 TEST RESULTS
DC Output (W)
40
65
90
150
200
250
300
400
442*
AC Input (W)
62
91
120
193
249
321
391
520
572
Efficiency
65%
71%
75%
78%
80%
78%
77%
77%
77%
Intake Temp (°C)
27
29
31
33
36
39
41
45
46
PSU Exhaust (°C)
31
34
37
39
42
44
46
51
53
Temp Rise (°C)
4
5
6
6
6
5
5
6
7
Fan Voltage (intake)**
5.3
5.3
5.3
5.3
6.7
10.0
12.5
12.6
12.6
SPL (dBA @ 1m)
21
21
21
27
32
37
40
40
40
Power Factor
0.60
0.61
0.62
0.64
0.65
0.66
0.66
0.66
0.66

NOTE: The ambient room temperature during testing
varies a few degrees from review to review. Please take this into account
when comparing PSU test data.

* See Section 3 on stability below

** See Section 6 for more information about the fan controller.

ANALYSIS

1. VOLTAGE REGULATION was within the 5% specified by ATX12V throughout
the test, and the +3.3V and +5V lines were typically within 2-3%. The +12V line
was consistently high throughout the test, but the total variance from high
to low was small. The biggest voltage drop on the +12V line was seen at 400W
and above, but it still stayed above 12V.

  • +12V: 12.24 to 12.54
  • +5V: 4.86 to 5.04
  • +3.3V: 3.27 to 3.32

2. EFFICIENCY was good for a model that does not claim to be
top-of-the-line. While we've regularly seen efficiency curves that peak in the mid
eighties, these are typically high-end models that cost significantly more. The best efficiency was not achieved in the SmartPower 2.0 until the 150W - 200W
range, which some PCs may demand under heavy loads. However, most systems
do not see sustained use at this level. Efficiency at the lower loads ( most systems operate was about average.

3. STABILITY

For the most part, the SmartPower 2.0 had no trouble powering the loads we placed
on it. However, one of
the protection circuits kicked in when we tried to go from 400W up to 444W.
This happened repeatedly, every time we tried to reach full load.
The power supply could be reset within ten seconds by cycling the
AC power switch, which suggests that the problem was an overly sensitive protection
circuit, not a failure.

The shutdown occurred with the +5V and +3.3V lines fully loaded and delivering
their combined maximum of 150W. Small loads ( -12V and +5VSB lines. A combined load of 21A (252W) on the two +12V rails could
be handled without problems. However, adding a single ampere (12W) to the +12V
line triggered an immediate shutdown. The same 12W increase could be achieved
by adding power to the +5V or +3.3V line without causing the power supply to
shut down, even though this exceeded the published specification for these lines.

It is possible (not likely, but possible) that the overcurrent protection was
legitimately shutting down the power supply, if the specifications on
the web site, not the box, are correct
(see page 2 of this review). Adding 12W to the +12V
line would have put the output power on the +3.3V, +5V, and +12V rails at 414W
? a pithy four watts over the "maximum" of 410W. However, as
mentioned above, adding a similar load to either the +3.3V or +5V line did not
have the same effect. The other factor to consider is that because the 12V line was actually at 12.25V at full load, the real load was about 6W higher than intended. But this seems a very small "overload" to cause instant shutdown.

We contacted Antec about this problem, and they sent us a
second sample to see if it would behave the same way. Fortunately, it did
not. The second sample reached the maximum of 444W load without any problem,
and stayed running at that output level for some time.

Because the inability to reach full power was probably the result of an overly sensitive protection
circuit, not a failure, the problem that we saw with the first sample is largely
trivial. No ordinary system is likely to draw more than half of the
load at which the first sample shut down. A dual processor, SLI system might peak around
400W, but such a system cannot be connected to this power supply without multiple
adapters.

4. POWER FACTOR was typical for a unit without power factor correction,
ranging from 0.60~0.66, increasing with power draw.

5. TEMPERATURE AND COOLING

The flow-through design of the SmartPower 2.0 works very well. The temperature
rise through the power supply stayed at just 5~6°C through
almost all of its output range. At lower loads, this is fairly normal, but as
the load increases, it is more impressive. Many power supplies
we've tested had a thermal rise of well over 10°C at 400W load, whereas the SmartPower
2.0 managed to keep it to just 6°C.

6. FAN, FAN CONTROLLER and NOISE

The test environment is live, so readings are higher than would be obtained
in an anechoic chamber readings, due to reflections and reinforcement of sound
waves off the walls, ceiling and floor.

As with every power supply we test, the positive wire of each fan was tapped
so we could measure the input voltage. The neutral line was tapped at one of
the common ground wires via an IDE drive connector. However, this method initially
gave us a reading of -12V ? obviously wrong. This implied that the fan
control circuit is completely separate from the rest of the power supply.

So, we also tapped the common wire of each fan. No matter what load was placed
on the PSU, both fans were always fed the same voltage, which should have meant
that they were always at roughly the same speed. However this was not the case:
The input voltage remained at 5.3V at low loads, but sometimes the exhaust fan
was spinning, and sometimes it wasn't. Since the voltage did not change, there
was no apparent reason for the rear fan to have suddenly started spinning.

For this reason, we were unable to determine experimentally how the rear (exhaust) fan is
controlled. One possibility is that the fan itself is thermally
controlled independently of the fan control circuit, but Antec could not verify
this yet. So, the voltages reported in the data table above reflect the input voltage
to the intake fan.

The fan control circuit seemed to have an odd side effect that dismayed many
users in our forums
: When the fan monitor cable is plugged into a motherboard,
the rear fan runs at full speed ? making it useless for a quiet computer.
However, unplugging the cable solves the problem and the fans behave as they
should. Antec informed us that this problem had been noted and corrected after the first shipment that went out to retail.

Without the fan monitor cable plugged in, the rear fan does not spin at
all when the temperature is low. This is excellent for silencers.
It means that the only source of noise is the intake fan in the middle of the
case, away from any direct paths to the user's ears. It also spins slowly enough
that it is probably close to or below the ambient noise level in most rooms, effectively making
it silent in a low power system. The low-profile
intake fan is quite well-behaved, even at the relatively high starting voltage
of 5.3V.

The exhaust fan begins to spin when the intake temperature reaches the mid-thirties ? at about 150W load in our test environment. The ambient temperature
during this test was a bit higher than usual, which caused the fan to start earlier
than it would have otherwise. The exhaust fan has a noticeable effect on the
noise. It is louder, and there is a small amount of whine from the motor. Fortunately,
the transition as the fan turns on is not very audible. There is enough hysteresis
in whatever is controlling the exhaust fan that it ramps up slowly and smoothly.
This was true of both fans: Changes in noise level were only audible when specifically
listened for.

Once the exhaust fan turns on, the noise signature rapidly deteriorates. The
intake fan also increases in speed with temperature, and by the time the intake temperature
has climbed above 34~35°C, it is no longer acceptable for use in a quiet system.
The twin 80mm fans sound worse than a single 120mm fan at the same measured
noise level because there are two separate bands of motor noise, both of which
are higher in pitch than a typical 120mm fan, making the noise harder to tune
out.

MP3 Sound Recordings of Antec SmartPower 2.0 SP-450

Antec
SmartPower 2.0 SP-450 @

Antec
SmartPower 2.0 SP-450 @ 150W (27 dBA/1m)

Antec
SmartPower 2.0 SP-450 @ 200W (32 dBA/1m)

There was no need to make recordings at higher power levels; it's simply too loud.

Sound Recordings of PSU Comparatives

Seasonic
Tornado 400 @ 65W (19 dBA/1m)

Seasonic
S12-430 @ 150W (19 dBA/1m)

Enermax
Noisetaker 600W (2.0) @ 150W (27 dBA/1m)

Nexus
92mm case fan @ 5V (17 dBA/1m) Reference

HOW TO LISTEN & COMPARE

These recordings were made with a high
resolution studio quality digital recording system. The microphone was 3" from
the edge of the fan frame at a 45° angle, facing the intake side of the fan to
avoid direct wind noise. The ambient noise during all recordings was 18 dBA or
lower.

To set the volume to a realistic level (similar to the original), try playing the Nexus 92 fan reference recording and setting the volume so that it is barely audible. Then don't reset the volume and play the other sound files. Of course, tone controls or other effects should all be turned off or set to neutral. For full details on how to calibrate your sound system to get the most
valid listening comparison, please see the yellow text box entitled Listen to
the Fans
on page four of the article
SPCR's Test / Sound Lab: A Short Tour.

CONCLUSIONS

The SmartPower 2.0 is a good choice for use in a quiet system as long as
power requirements are not too heavy. Its noise floor is close to that of our
low noise reference, the Seasonic S12, and it is considerably cheaper. That
said, it cannot compare to the noise level of the S12 at high loads in a typical high-end system. Although they start out at the same noise level
and even stay close to level, beyond around 150W output, the SmartPower gets noisier
more quickly and at a lower temperature than the Seasonic. The low noise of the SmartPower 2.0 at low levels can be attributed
to the intelligent flow-through airflow design that cools it very effectively.

Given the straight-through airflow design of this PSU, it is probably a good candidate for use in an Antec P180 case, where the thermal isolation of the PSU would ensure lower temperature at the intake, and thus keep the PSU running at idle-quiet levels even at high load. No other fan would be needed in the bottom chamber of the P180. However, extension cables would be needed for the 2x12V and main ATX connectors to use this PSU in a P180.

The inability of our first sample to deliver its full rated load is a fairly
minor issue, related more to the artificial conditions of our test setup and
luck of the draw than a serious design flaw. It would be more a cause for concern
if the shutdown occurred at a lower load or if it was not related to a protection
circuit. More serious is the short length of the cables, which restricts the cases in
which the SmartPower 2.0 can be used and can make it difficult to route cables.

All in all, the SmartPower 2.0 is a solid choice for a
low-noise system. Those who want a top-of-the-line "designer"
power supply are advised to look elsewhere, but if functionality and price are
your primary requirements, the SmartPower 2.0 should fulfill your needs.

* * *

Much thanks to Antec
for the opportunity to examine this power supply.

POSTCRIPT: Efficiency Correction

October 22, 2005

Recently, we discovered that our power supply testing equipment and methodology were providing erroneously high efficiency results. In general, the biggest errors occurred at higher
output load points above 300W. At lower output levels, the efficiency error
was often no more than one or two percentage points. No other tested parameters were significantly affected.

Through a fairly arduous process of discovery, analysis and old fashioned problem solving, we modified our testing equipment and methodology to improve the accuracy of the efficiency results and described it all in the article SPCR's PSU Test Platform V.3. As part of this revision, we re-tested most of the power supplies on our Recommended PSU List. In most cases, the same sample was used in the second test.

The corrected and original efficiency results for all the re-tested PSUs are shown in in the article, Corrected Efficiency Results for Recommended Power Supplies. The relative efficiency of the tested power supplies has not changed.
If the tested PSUs are ranked by efficiency, the rankings remain the same whether we use the original results or the new results.

This
data is also being added to relevant reviews as postscripts like this one.


CORRECTED EFFICIENCY: Antec Smartpower 2.0 - 450

Target Output


40W



65W



90W



150W



200W



250W



300W



450W


Actual Output
42.1W
63.6W
86.7W
149.3W
198.5W
254.5W
299.4W
447.7W

Efficiency

Corrected
64.8%
73.1%
74.7%
78.1%
79.7%
79.1%
78.4%
75.1%

Original
65%
71%
75%
78%
80%
78%
77%
77%

In this case, our original efficiency calculations were either dead on or slightly too low except at maximum output, at which point it was a bit too high.

Discuss this article in the SPCR Forums.

Sections: 

Google

www SPCR