The BitFenix Whisper M 450W 850W PSU Review

BitFenix is a comparatively new company that quickly became an established brand name via their PC case designs. Today BitFenix is still focused primarily on cases but the company is slowly diversifying, offering supplies for case mods, audio products, and power supply units (PSUs). Ever since the company’s founding in 2010, we reviewed several of their case designs, but not any of their other products. Today we are having a look at their recently released ATX PSU series, the Whisper M.

The Whisper M is not BitFenix’s first attempt to diversify towards the PSU market. Their first attempt was about three years ago with the Fury series, a PSU series that heavily weighted towards aesthetics and with a relatively hefty price tag at the time of its release. This time around BitFenix is taking a somewhat different approach, trying to balance performance with aesthetics, all while maintaining a competitive price tag, especially in a very competitive market.

BitFenix Whisper M series – MSRP Prices
BWG850M BP-WG850UMAG-7FM $119
BWG750M BP-WG750UMAG-7FM $109
BWG650M BP-WG650UMAG-7FM $89
BWG550M BP-WG550UMAG-7FM $79
BWG450M BP-WG450UMAG-7FM $69

The Whisper M series consists of five units ranging from 450 to 850 Watts, in 100 Watt steps. In this review we are having a look at the top and tail of the series, the 450W and the 850W units. Both units are fully modular, they boast impressive on-the-box performance specifications, they are 80Plus Gold certified and get that rating at 50 °C, all while parading with a 7-year warranty. The Whisper M units also have a multi 12V rail design, which is something that we have not seen being implemented in quite some time. The MSRP pricing is $69 and $119 for the 450W and the 850W units respectively, which is be more than reasonable if the units prove to be good performers.

BitFenix Whisper M 450W ( Rated @ 50 °C )
AC INPUT 100 – 240 VAC, 50 – 60 Hz
RAIL +3.3V +5V +12V +12V2 +12V3 +5Vsb -12V
MAX OUTPUT 20A 20A 25A 25A 25A 2.5A 0.3A
100W 450W 12.5W 3.6W

BitFenix Whisper M 850W ( Rated @ 50 °C )
AC INPUT 100 – 240 VAC, 50 – 60 Hz
RAIL +3.3V +5V +12V +12V +12V +12V +5Vsb -12V
MAX OUTPUT 22A 22A 25A 25A 40A 40A 2.5A 0.5A
120W 850W 12.5W 6W

Packaging and Bundle

The company supplies the Whisper M series in an aesthetically simple but practical cardboard box. Although the artwork is limited to a partial picture of the unit itself, the rear and sides of the box are full of graphs and charts that depict all of the unit’s core features. One could notice that the text could use some editing by just looking at the front of the box, where it reads “Silence Perfromance” (two nouns, one of them misspelled). The walls of the box are very strong and the unit is packed between thick polyethylene foam pieces that are offering ample shipping protection.

Most likely in an effort to keep the costs low, BitFenix supplies only the basics alongside with their Whisper M PSUs. Inside the box we only found the necessary AC power cable, a few cable straps, four black mounting screws and a basic user’s manual (with the same spelling error). Both units share the exact same bundle, only the number of the supplied modular cables differs.

All of the Whisper M units are fully modular, with “flat” ribbon-like cables. The wires and the connectors are all entirely black. An interesting feature here is the bulky connector of the 24-pin ATX cable. The large plastic cover is not there solely for aesthetic purposes but it actually hides three solid-state capacitors that are being used for extra ripple suppression. This is the first time that we have seen the designer of a PSU employing capacitors outside of the unit’s body. 

Connector Whisper M 450W Whisper M 850W
ATX 24 Pin 1 1
EPS 4+4 Pin 1 2
EPS 8 Pin
PCI-E 6+2 Pin 2 6
PCI-E 8 Pin
SATA 8 12
Molex 4 4

External Appearance

Physically, the 450W version of the Whisper M is almost entirely identical to the 850W version. The only real way to tell the two units apart is to look at the large stickers with their electrical specification at the top of the chassis or know the cable layout variations in the series. Both units are built in a standard-size ATX chassis that is 160 mm long and sprayed with a matte black paint. The matte paint is very well applied but it is easy to scratch and heavily prone to fingermarks.

A square opening at the bottom of the chassis reveals the cooling fan and is covered with a finger guard that uses a parallel grating. The only round part of the metallic design is the company’s badge over the fan’s engine. Black/Yellow stickers decorate both sides of the PSUs, without any mention of any figures or model numbers. Only the large stickers at the top of the chassis has the full electrical specifications of the PSU printed on it.

The front side of the PSU is littered with the connectors for the many modular cables. Here the 850W version has two connectors more, for the two additional PCI Express cables that it has.

Internal Design

As expected, considering the large difference in power that the two PSUs have, their first major difference is the 135 mm cooling fan. Both fans are supplied by Martech, a rarely-seen Chinese manufacturer, and both are of the same series. The 450W version comes with the DF1352512SEMN and the 850W version employs the DF1352512SEHN, with the main difference being their maximum rotational speed – 1500 RPM and 1800 RPM respectively. Both are using “Hydro” bearing engines, which are advanced forms of regular sleeve bearings.

The OEM behind the Whisper M units is Channel-Well Technology (CWT), a company that we are very familiar with. However, this is a design that we have never encountered prior to this date. First and foremost, it is worthwhile to mention that both PSUs are based on the same platform, meaning that all of the different versions of Whisper M should all be on this platform (it would be rare for a mid-powered unit to differ). A quick glance reveals that there are no great differences between the two PSUs other that the sizing of some of the components. We were actually bewildered to see that the 850W version is using the same heatsinks as the 450W version does, despite having nearly twice the power output, hinting that the employment of the more powerful fan was more of a necessity and less of a precaution.

The internal design of the Whisper M units is very clean, with minimal use of wires at all. The secondary board with the modular cable connectors is soldered directly onto the main board, hinting that CWT has designed this particular platform for modular-only PSUs. We can see that both units are sharing the same filtering stage, with four Y capacitors, two X capacitors, and two filtering inductors. The heatsink of the input conversion bridge is identical, but the bridge itself is (vastly) different between the two units. Specifically, the 450W version employs a GBU606 that is capable of 6 Amperes, whereas the 850W version is making use of an oversized GBU15L06, a bridge capable of 15 Amperes.


BitFenix Whisper M 450W – Internal View

Another major component difference between the two units are the PFC components, with the 450W unit using a Nichicon 330μF capacitor, whereas the 850W version has a Nippon Chemi-Con 680μF capacitor installed. The APFC inductor is also notably larger and the active components are significantly more powerful. Two transistors form a relatively simple half-bridge primary inversion side with its efficiency boosted by an LLC resonant converter. The four secondary side conversion stage transistors that generate the 12V output are attached to the underside of the main PCB and cooled by the silvery heatsinks next to the main transformer. The 3.3V and 5V outputs are generated by DC-to-DC circuits found on the small vertical PCB.


BitFenix Whisper M 850W – Internal View

It is worthwhile to notice that both units are using filtering capacitors of the same type and size at the secondary side for filtering. Nippon Chemi-Con supplies the electrolytics and most solid-state capacitors, with the rest of the solid-state capacitors coming from Nichicon.

Cold Test Results (Room Temperature)

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M  40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs – 2014 Pipeline post.

Both the 450W and the 850W version of the BitFenix Whisper M PSU honored their 80Plus Gold certification without issues. The 450W version actually fared a little better, with an average nominal load range (20%-100%) efficiency of 91.2%. It is only slightly higher than that of the 850W version (91%), but we can see the 850W version only barely surpassing the 92% mark at 50% load, where the 450W version exceeded it with ease, peaking at 92.5%. We can also notice that the 450W model is substantially more efficient with loads lower than 300 Watts. This is not an issue of any kind; the narrow power range of the 450W model simply allows it to perform much better when lightly loaded. The powerful 850W model technically reaches its nominal load range with a load of 170 Watts and above, in the range where the 450W model is already moving towards peak efficiency.

With loads lower than 300 Watts, the higher efficiency of the 450W model allows it to maintain lower internal operating temperatures, but not lower noise levels. The fans of both units seem to copy each other, with the fan of the 850W model simply speeding up further with loads above 450 Watts. Regardless, the sound pressure level with loads below 300 Watts is below 34 dB(A) with both units, which corresponds to a very soft humming noise if one gets an ear very close to the PSU. 

Hot Box Test Results

This new platform probably delivers the best power quality that we have previously seen from any Channel-Well Technology design. The ripple suppression of the 450W unit is amazing, with the 12V line registering a maximum of 20 mV and the 3.3V/5V barely reading a voltage ripple of 12 mV. 

BitFenix Whisper M 450W – Main Output
Load (Watts) 91.01 W 227.31 W 339.04 W 450.63 W
Load (Percent) 20.23% 50.51% 75.34% 100.14%
  Amperes Volts Amperes Volts Amperes Volts Amperes Volts
3.3 V 1.69 3.36 4.22 3.35 6.33 3.32 8.44 3.32
5 V 1.69 5.06 4.22 5.05 6.33 5.03 8.44 5.02
12 V 6.33 12.13 15.83 12.12 23.75 12.05 31.66 12.01
Line Regulation
(20% to 100% load)
Voltage Ripple (mV)
20% Load 50% Load 75% Load 100% Load CL1
3.3V + 5V
3.3V 1% 8 8 10 12 8 10
5V 0.9% 8 10 10 12 8 12
12V 1% 10 14 16 20 16 12

We can see that the 850W version delivers similar performance under the same loading conditions, with the voltage ripple readings increasing only at loads far beyond the capacity of its smallest sibling. Still, the 32 mV voltage ripple on the 12V line is an outstanding figure under a load of 850 Watts. The voltage regulation is nearly identical for every line of both units, with an average of just 1%.

BitFenix Whisper M 850W – Main Output
Load (Watts) 171.98 W 429.31 W 640.99 W 851.22 W
Load (Percent) 20.23% 50.51% 75.41% 100.14%
  Amperes Volts Amperes Volts Amperes Volts Amperes Volts
3.3 V 2.01 3.4 5.02 3.39 7.53 3.38 10.04 3.37
5 V 2.01 5.1 5.02 5.08 7.53 5.06 10.04 5.05
12 V 12.78 12.12 31.94 12.11 47.92 12.05 63.89 12
Line Regulation
(20% to 100% load)
Voltage Ripple (mV)
20% Load 50% Load 75% Load 100% Load CL1
3.3V + 5V
3.3V 0.9% 8 10 10 12 10 14
5V 1% 8 10 16 16 10 16
12V 1% 10 16 24 34 32 18

The higher ambient temperatures in our hotbox testing had almost no impact on the energy conversion efficiency of the Whisper M 450W PSU at all, with the unit technically maintaining 80Plus Gold efficiency levels even under such conditions. Respectively, the efficiency of the Whisper M 850W PSU dropped by an average of just 0.5%. The drop is a little greater than that of the 450W model, but minimal nonetheless. These figures suggest that the components are of excellent quality and adequately oversized, allowing the Whisper M PSUs to seamlessly operate under the most adverse of system conditions.

Considering the small heatsinks and especially because the 850W version is using the exact same heatsinks as the 450W version, we expected to see higher operating temperatures during our testing. However, it seems that BitFenix went with a simple, yet effective way of fan speed control that completely ignores the load and adjusts the fans only according to their internal temperature.

As a result, the Whisper M units cannot really operate quietly in a very hot environment, but the internal temperatures will always remain at perfectly safe levels.


In this review we had a look at two PSUs from the Whisper M series. Whisper M is BitFenix’s second attempt to market a competitive PSU series. Their first attempt was with the Fury, a PSU series that heavily relied on its aesthetic design but did not really stand out of the crowd at the time. BitFenix capitalized on the experience they gained from this endeavor and took a different approach with the new Whisper M series, balancing the unit between aesthetics, performance, quality and cost.

The thermal control of the Whisper M units is simplistic, and therefore the acoustics strongly depend on the internal temperature of the case. This may be a good or bad thing, depending on how well-cooled the system is. It is possible that good builds may allow the Whisper M to stay completely quiet until even if it is heavily loaded, whereas restrictive setups could force it to spin up its fan even while the system is idling. One thing is for certain – the power rating has very little to do with the acoustics performance here given how close both units perform audibly. It would actually be harmful to purchase a significantly oversized model hoping to get lower noise levels, as the electrical performance within the load range of the system would decline.

Perhaps the most impressive feature of the Whisper M series is their power quality. Both units had a voltage regulation of just 1% on every one of their lines and the ripple was minimal even when the PSUs were heavily loaded. The OEM, Channel Well Technology, played no small part. After all, no matter how much BitFenix might have tweaked it, the original platform is a CWT design. This platform is specifically designed for modular PSU designs, as the PCB that holds the modular connectors is soldered directly onto the main PCB, virtually eradicating the need of cables that can adversely affect both the efficiency and the power quality of the PSU. The overall design is very clean and the assembly is exceptional, with no manufacturing flaws to the found, and the suppliers of the components are all highly reputable. The use of top quality components also allows the Whisper M units to maintain their excellent performance under high ambient temperatures. It is no coincidence that BitFenix covers these units with a seven-year warranty.

The cherry on top here is the retail pricing. According to BitFenix’s announced MSRP, the Whisper M PSUs are very competitively priced. Less than $70 can get you a fully modular PSU, with great overall performance and backed up by a seven-year warranty, with enough power for a modern single-GPU gaming PC. The company certainly used every bit of experience they gained since their first attempt and managed to bring a truly competitive series into a highly saturated market. The only issue with the Whisper M series is their current availability; it is very difficult to find a shop that has any model of the series in stock and, when they do bring stock in, the units are usually gone in a matter of hours. Hopefully BitFenix will resolve this issue soon and we are going to see a healthy inventory available, at least on the major retailers/e-tailers.


Leave a Reply

Your email address will not be published. Required fields are marked *