Enermax Modu87+ 500W 80Plus Gold

The most efficient ATX12V power supply in the world with a sensible power rating is the Enermax Modu/Pro 87+ 500W. It’s also the quietest, by a slim margin. Alas, finding one to buy is a challenge.

Energy efficiency is such an important part of power supply marketing these
days that the names of Enermax’s most advanced models come from their base efficiency:
The Modu82+ of 2008,
for example, and today’s Modu87+ and Pro87+ lines. The number 87 also happens
to be the minimum efficiency requirement of the 80
PLUS Gold certification, which we
wrote about a couple of years ago. The symbol "+" is also a not-so-subtle
echo of 80 PLUS.

An aside: The folks at Ecos Consulting who run 80 PLUS must be
laughing all the way to the bank. When they consulted me in San Francisco at
IDF 2005 a few months before the program was announced, none of us had any real
inkling that less than five years hence, there would be some 2200 power supply
models on the 80 Plus approved list. That’s an average of about 500 units annually.
Ecos wanted my input because SPCR had been testing power supplies for efficiency
and posting the results publicly since 2002, before hardly anyone was even talking
about the idea. One of our industry friends suggests that we should "promote
SPCR as the tempered and learned wise man in the midst of a bunch of young upstarts
who’ve only been on the power-conscious beat a year or so." (There,
I’ve started, Damon! 😀 )

Enermax has been a major high performance brand in power supplies for decades
now, so it’s no surprise that it is among the few retail brands offering 80
PLUS Gold certified models. Seasonic was the first to offer Gold level efficiency,
with its X-650 and X-750 models, but Enermax followed only about a month later,
in late 2009, with a larger number of models. The Enermax global site lists
six models in the Modu87+ series, rated 500W to 900W, and three models in the
Pro87+ series, 500W, 600W and 700W. The two series are identical, except for
the modular output cabling of the Modu series. The table below summarizes the
various requirements of the program.

Long time readers of SPCR power supply reviews are probably aware than it’s
harder for lower power models to achieve the Gold certification, not the high
power models. The issue is that every power supply has a bell-shaped curve of
efficiency, which is highest in the middle and lower at the high and low power
extremes. In an absolute sense, the lower the power output, the harder it is
to maintain high efficiency. For an 800W model, 20% load is 160W. To achieve
87% efficiency at this power level requires advanced technology, but it’s already
being done by lower power 80 PLUS Silver models. For a 500W model, 20% load
is only 100W. To achieve 87% at this power load is a more difficult task, requiring
not only the most advanced components and circuitry but extremely low energy
losses at every stage within the power supply.

The Enermax Modu87+ and Pro87+ 500W models are the lowest power Gold certified
retail ATX12V PSUs on the 80 PLUS approved PSU list. This is significant. Among
the better known and distributed retail PSU brands, only Seasonic has anything
close in power, currently, the SS-550LT, which is essentially part of the X
series. The Seasonic and Enermax models were tested and approved by 80 PLUS
in the last quarter of 2009, so there’s been time for production to ramp up
and for good distribution. All of these models are missing in action, however;
they still cannot be found on line or in brick-and-mortar shops. Why is this
so?

It could be that the cost of producing these lower rated 80 PLUS Gold models
is not justifiable given the price they can fetch, and given the higher profitability
of the higher rated models. Perhaps as production volume of the higher power
models increases, the cost of the advanced components used within will drop,
and these lower power models will appear on the market — at prices enthusiasts
can justify. For now, the most moderately rated Gold PSU model in US/Canada
remains the Seasonic X-650. One comment from enermax is that the decision to
distribute the 500W models in the Americas has not been made yet; they are already
available in many EU countries where demand for lower power models is a bit
higher.

Note: Anyone who browses through the 80 PLUS database will see
many Gold certified models under 500W. Virtually all of these are OEM models
made specifically for major computer makers (such as Dell, HP, etc), often in
custom form factor, and generally unavailable on the retail market. Just a few,
short output cables and no detachable ones are de rigueur, in order to
minimize losses through cables.

PACKAGING & FEATURES

Please note that our review and commentary refer mainly to the Modu87+ 500W,
although a Pro87+ 500W was also examined. They are identical except for the
differences that arise from the Modu87+ having detachable cables.

Black and gold are the colors they chose for both Modu and Pro 87+. The package for the Modu87+ 500 contains a bunch of detachable cables, a pouch for the cables, velcro straps, user manual, AC cable. And the power supply itself.

A 500W power supply is plenty for a typical PC. None of the output
lines are likely to come anywhere near their rated maximum during ordinary use.
Ordinary computer users can easily get by with half as much capacity, but 500W
is still considered a "small" power supply these days.

VISUAL TOUR

The finish for the Modu87+ and Pro87+ is glossy black, with gold / yellow contrasts.
The gold fan blades look a bit garish, but they’ll be invisible inside a case.
All the cables, attached and detached, are sleeved.

The black and gold color scheme continues. Wire intake grill for fan, hex-shaped holes on exhaust; this are pretty standard. It is a 139mm diameter fan instead of the more typical 120mm. The casing is sealed except for the intake and exhaust. This socket wire clip is the CordGuard in operation.

OUTPUT CABLES

Attached

• 1 – 24P MainBoard (main ATX) – 55cm
• 1 – 4P+4P CPU (Aux12V) – 60cm

Modular

There are only four modular cables, which is appropriate for the power rating
of this model. One of the cables combines two SATA and two standard 4-pin Molex
connectors, which is really nice to minimize cables in a minimalist build.

INSIDE

Components of many colors are on the inside. The blue of the heatsinks and
the gold of the fan blades stand out.

TESTING

For a fuller understanding of ATX power supplies, please read
the reference article Power
Supply Fundamentals. Those who seek source materials
can find Intel’s various PSU design guides at Form
Factors.

For a complete rundown of testing equipment and procedures, please
refer to SPCR’s
PSU Test Platform V4.1. The testing system is a close simulation of
a moderate airflow mid-tower PC optimized for low noise.

Acoustic measurements are now performed in our anechoic chamber with ambient level of 11 dBA or lower, with a PC-based spectrum analyzer comprised of SpectraPLUS software with ACO Pacific microphone and M-Audio digital audio interfaces.

In our 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.

The 120mm fan responsible for "case airflow" is deliberately
run at a steady low level (6~7V) when the system is run at "low"
loads. When the test loads become greater, the 120mm fan is turned up to a higher
speed, but one that doesn’t affect the noise level of the overall system. Anyone
who is running a system that draws 400W or more would definitely want more than
20CFM of airflow through their case, and at this point, the noise level of the
exhaust fan is typically not the greatest concern.

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 too many
variables in PCs and 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 pretty good overall representation, but it is not quite the same as an extended
meeting in person.

REAL SYSTEM POWER NEEDS: While we test the PSU to full
output 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 40W and 300W, because it is the power range
where most systems will be working most of the time. To illustrate this point,
we
conducted system tests to measure the power draw of several actual systems
under idle and worst-case conditions. Our most power-hungry overclocked
130W TDP processor rig with an ATI Radeon X1950XTX-512 graphics card drew ~256W
DC peak 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 the most power hungry dual
video cards today might draw as much as another 150~200W, but the total should
remain under 500W in extrapolations of our real world measurements.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that PSU fan speed varies with temperature,
not output load. A power supply generates more heat as output increases, but
this 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:

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 temperature number that is comparable between different reviews,
as it is unaffected by the ambient temperature.

TEST RESULTS

The ambient temperature was 22~23°C, and the ambient noise
level was 10~11 dBA. AC input voltage was 118~121V.

1. EFFICIENCY — This is a measure of AC-to-DC conversion
efficiency. The ATX12V Power Supply Design Guide recommends 80% efficiency or
better at all output power loads. 80% efficiency means that to deliver 80W DC
output, a PSU draws 100W AC input, and 20W is lost as heat within the PSU. Higher
efficiency is preferred for reduced energy consumption and cooler operation.
It allows reduced cooling airflow, which translates to lower noise. The 80 Plus
Gold standard requires a minimum of 87% efficiency at 20% load, 90% efficiency
at 50% load, and 87% efficiency at full rated maximum load.

Our samples met 80 Plus Gold requirements. 80% efficiency was
reached at a very low 50W; by 90W, it was already at 86%. A broad peak of >90%
efficiency was maintained from about 170W to 330W load. Beyond that, it drooped
a bit as expected, down to ~87% at maximum load.

The Seasonic X-650
reached slightly higher peak efficiency and maintained it to a higher load,
which is expected given its higher power rating. The overall efficiency curves
of the two models look very similar.

2. DC VOLTAGE REGULATION refers to how stable the output
voltages are under various load conditions. The ATX12V Power Supply Design Guide
calls for the +12, +5V and +3.3V lines to be maintained within ±5%.

Unless a unit goes into overload, it’s rare that we see significant
problems with voltage regulation with the higher quality PSUs SPCR generally
examines. The Enermax Modu87+ is no exception — it was nearly always within
±2% on any line. With the exception of the cross-load test (which is
strenuous), the +12V line stayed above the specified +12V at all times.

3. AC RIPPLE refers to unwanted "noise"
artifacts in the DC output of a switching power supply. It’s usually very high
in frequency (in the order of 100s of kHz). The peak-to-peak value is measured.
The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V
line and 50mV on the +5V and +3.3V lines. Where voltage regulation is a measure
of variance from spec, ripple is more a measure of tolerance: How much the voltage
is changing at any given time. Ripple is of interest to over- and under-clockers
who push their systems to the limits of what they are actually capable
of rather than relying on what the specs say they should be capable of.

Ripple on the 12V line was a little higher than we’ve seen in
other top units, but still well within spec at <47mV all the way to full
load. The 5V and 3.3V lines exhibited very low ripple, under 17mV and 12mV at
all levels.

4. POWER FACTOR is ideal when it measures 1.0. In the most
practical sense, PF is a measure of how "difficult" it is for the
electric utility to deliver the AC power into your power supply. High PF reduces
the AC current draw, which reduces stress on the electric wiring in your home
(and elsewhere up the line). It also means you can do with a smaller, cheaper
UPS backup; they are priced according to their VA (volt-ampere) rating.

As is the case for most units with active power factor correction
(which, these days, is most reputable brands), PFC was close to perfect, starting
at 0.96 for the minuscule 20W load, and staying at 0.99 through most of the
operating range.

5. LOW LOAD TESTING revealed no problems starting at very
low loads and it stayed operational with no load applied. It also started without
a load, with a very low 4.3W AC power draw.

6. LOW & 240 VAC PERFORMANCE

The power supply was set to 400W load with 120VAC through the
hefty variac in the lab. The variac was then dialed 10V lower every 5 minutes.
This is to check the stability of the PSU under brownout conditions where the
AC line voltage drops from the 120V norm. Most full-range input power supplies
achieve higher efficiency with higher AC input voltage. SPCR’s lab is equipped
with a 240VAC line, which was used to check power supply efficiency for the
benefit of those who live in 240VAC mains regions.

Efficiency improved a little over 3% with 244VAC input at this
load. The sample passed the 100VAC minimum input without any issues. Neither
voltage regulation nor ripple changed appreciably during the test.

7. TEMPERATURE & COOLING

The Modu/Pro 87+ 500W samples kept temperature rise to under 10°C
until over 200W load. The fan did not speed up even when the temperature rise
went up to 12°C at 250W load, but it did speed up at 300W load, to an undetermined
RPM and reached 14 dBA@1m at 300W. By 400W, the fan was spinning fast enough
to make 20 dBA@1m SPL, and bring the temperature rise back down, to just 9°C.
At full load, where Enermax says the fan spins at 1000 RPM, the temperature
rise was still a modest 17°C. This is excellent cooling, especially in light
of the slow, quiet fan. As with all really quiet PSUs, don’t count on the Modu/Pro
87+ 500W to remove much heat from your system; make sure your cases fans do
their job.

7. FAN, FAN CONTROLLER and NOISE

The fan controller holds the fan speed down until absolutely necessary.
The fan speed didn’t budge from its start 330 RPM until the 300W output load
was reached. The noise curve is a flat 11 dBA@1m SPL up to that point, and the
reality is that the actual level could have been even lower, since 11 dBA is
the noise floor of our anechoic chamber.

Quite simply, these PSUs are not audible at under 300W load in
our test rig, not until one’s ear is virtually pressed up against the exhaust
grill. The sound was a tiny hum.

Amazingly, even at full load, the SPL was a mere 23 dBA@1m, and
this is with the fan spinning, apparently, at 1000 RPM. Acoustically, at 500W
load, very few other tested PSU come close. The closest is the Nexus NX-5000
at 25 dBA@1m, but its fan starts ramping up at a much lower power level and
is much more audible throughout the middle power range. The Nexus is also much
less energy efficient, with nearly 5% difference at mid power peak.

In a desktop PC without a high power (>100W) graphics card,
regardless of the other components, this PSU is probably never going to be audible.
Exceptions might be if your ambient temperature is hot, say >35°C, or
you try to run with no other fans in your system. If you do run a gaming video
card with >100W peak power, along with some other hefty components like overclocked
125W TDP Phenom or i7 processor and get >300W load, the PSU will become audible
at times… but most likely, it will be drowned out by other fans ramping up
to keep the other components cool enough.

The quality of the noise is moot until the 20 dBA@1m is reached
at the 400W load. Below that, it really was too quiet for sound quality to matter.
At the 20~23 dBA@1m level, there was some buzzing and humming, but these sounds
were audible only from very close up. In normal use, these PSUs are essentially
silent.

11 dBA@1m at up to 250W. Yes, the fan is spinning here, at about 320 RPM according to our calibrated strobe light. There’s no real difference between the ambient (red line) and when the PSU is on. 14 dBA@1m @300W. The fan noise is clearly visible here, mostly concentrated between 150 and 900 Hz. There’s a touch of buzzing centered around 200 Hz. Above 1,000 Hz, there is nothing. 20 dBA@1m@400W. The 200 Hz buzzing has become more significant. Most of the noise is between 150 Hz and 2 kHz, although there is some ultrasonic noise at well over 10 kHz, which can be heard from up very close as electronic noise.

One thing we’ve been examining is how the power supply performs
outside the tough thermal conditions of our standard test. The
recent popularity of cases that isolate the power supply from the rest of the
system make this a relevant question, as the cooler intake air allows the fan
to run slower and quieter. We examine this by rerunning some of the high load
tests with the power supply in free air, away from the tough thermal conditions
of the hot-box.

The results were quite dramatic: Even at full load, the SPL remained
at just 18 dBA. The fan did not speed up until maximum load, and even then it
did not reach full speed. This suggests that in a case with isolated external
intake vent for the PSU, the Enermax 87+ 500W models would remain silent to
just short of full power load.

COMPARISONS

The comparison table below shows the SPL versus Power Load data on all the
PSUs tested in the anechoic chamber thus far. It’s difficult to rank them, as
the measured SPL varies with power load. The units which are quietest at minimum
load are not always the quietest at midload (100W~300W), which may make them
louder in actual use. Then there’s the noise level at 400W and up, which will
determine the quietest PSUs for high power gaming rigs, during actual gaming.

The Enermax Modu/Pro87+ 500W actually manages to be quieter than any other
PSUs at every load, with the sole exception of <100W where
the Seasonic X-650 fanless operation may have a dB or two edge — if indeed
the 11 dBA@1m level is audible to anyone. Up to 250W, it is simply inaudible,
period. The edge over the closest competitors is small, but it’s there. At 300W
and above, it becomes somewhat audible but still quieter than all the other
PSUs. The Nexus Value 430 edges it by one dBA at 400W, but it is substantially
noisier from from about 200W on up, so that’s a false edge; in actual use, the
Nexus will be more audible more of the time. Overall, other than completely
fanless models, these Enermax Modu/Pro87+ 500W models are the quietest power
supplies we’ve tested.

Caution: Please keep in mind that the data in the above table is specific to the conditions of our test setup. Change the cooling configuration, the ambient temperature and any number of other factors, and you could change the point at which the fans start speeding up, as well as the rate of the rise in speed. The baseline SPL is accurate, however, probably to within 1 dBA.

MP3 SOUND RECORDINGS

These recordings were made as 24-bit / 88 kHz WAV files with a high
resolution, lab quality, digital recording system inside SPCR’s
own anechoic chamber (11 dBA ambient), then converted to LAME 128kbps
encoded MP3s. We’ve listened long and hard to ensure there is no audible degradation
from the original WAV files to these MP3s. They represent a quick snapshot of
what we heard during the review.

These recordings are intended to give you an idea of how the product sounds
in actual use — one meter is a reasonable typical distance between a computer
or computer component and your ear. The recording contains stretches of ambient
noise that you can use to judge the relative loudness of the subject. Be aware
that very quiet subjects may not be audible — if we couldn’t hear it from
one meter, chances are we couldn’t record it either!

Each recording starts with 6~10 seconds of room ambient, followed
by 10 seconds of the product’s noise and various settings. For the most
realistic results, set the volume so that the starting ambient level is just
barely audible, then don’t change the volume setting again while comparing all
the sound files.

• Enermax
  Modu/Pro87+ 500 at various loads in anechoic chamber at one meter
  — idle to >250W (11 dBA@1m)
  — 300W (14 dBA@1m)
  — 400W (20 dBA@1m)
  — 500W (23 dBA@1m)

Sound Recordings of PSU Comparatives in the Anechoic Chamber

• Seasonic
  X-650 at various loads in anechoic chamber at one meter
  — idle to >150W (ambient of chamber – 11 dBA@1m)
  — 200W (12 dBA@1m)
  — 250W (14 dBA@1m)
  — 300W (16 dBA@1m)
  — 400W (31 dBA@1m)

• Enermax
  Eco80+ at various loads in anechoic chamber at one meter
  — idle to >90W (11 dBA@1m)
  — 200W (16 dBA@1m)
  — 250W (19 dBA@1m)
  — 300W (26 dBA@1m)
• Seasonic
  M12D 850W at various loads in anechoic chamber at one meter
  — idle to >350W (14 dBA@1m)
  — 400W (24 dBA@1m)
  — 500W (37 dBA@1m)
• Antec
  Signature 650 at various loads in anechoic chamber at one meter
  — idle to 250W (15 dBA@1m)
  — 250~300W (18 dBA@1m)
  — 400W (28 dBA@1m)

CONCLUSIONS

The best of the high efficiency, quiet power supplies have been
truly impressive in our recent reviews. The Enermax 80 PLUS Gold certified 500W
models are the most impressive in some ways, with the best noise profile of
any power supply tested to date. The acoustic performance is such that the average
user will be hard pressed to tell whether the power supply is on, at least not
by the sound, because these models remain inaudible even at over 50% of rated
power load.

Our experience tells us that unless you run a high power video
card, your system is not likely to crest 250W, and at such a power level, the
fan in these Enermax power supplies will not speed up past the 330 RPM start
speed, where it registers barely 11 dBA@1m. This is inaudible in most rooms
for most people. In a computer case where the PSU has its own separate intake
vent — like the Antec P180 series, the Silverstone GD05 or the Fractal
Define — the Modu/Pro87+ 500W noise may never rise above that 11 dBA level.

Despite the low noise and slow fan speed, self cooling in the
Modu/Pro87+ 500W is fine, at least at moderate ambient room temperature. Perhaps
if ambient room temperature gets to be tropical summer hot, say 35°C or
hotter, you might want to consider speeding up your case fans, but most users
in such environs already know what they have to do for PC survival.

Electrically, these Enermax Gold certified PSUs also deliver excellent
performance. Perhaps not the very best in any single category, but plenty good
enough overall to be considered top tier, and better than any computer really
calls for. They won’t let you down. They also have a few niceties like a fan
that keeps blowing after power off to ensure rapid cooling, and an AC cord clip
to prevent accidents.

Alas, it’s disappointing to discover that like the SS-550LP, Seasonic’s
most modestly rated 80 PLUS Gold model, the Enermax Modu/Pro87+ 500W models
cannot be found for sale in the Americas at this time. This is despite their
official release announcement at the start of the year, some 4-5 months ago.
They are available in some EU countries, however, and with the higher 220~240VAC,
the efficiency for EU users will be even higher, up 2-3% on average. So as it
stands, the Seasonic X-650 remains the most moderately rated 80 PLUS Gold efficiency
power supply that’s widely available in the US and Canada. We can only hope
that Enermax steps up quickly with the 500W models on this continent, as tech
geeks are as fickle and flighty as any consumer group.

Much thanks to Enermax
for these review sample.

Enermax Modu/Pro87+ 500W wins the SPCR Editor’s Choice Award.

* * *

SPCR Articles of Related Interest:
Power Supply Fundamentals

Recommended Power Supplies
SPCR PSU Test Rig V.4
Seasonic X-650: Seasonic Hits
Gold
Seasonic M12D-850W
Enermax Modu82+ 625W
Antec CP-850: Unique PSU with Top Performance
Nexus NX-5000 Silent PSU

* * *

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