Be Quiet! is a German manufacturer that mainly produces PC cases, power supply units (PSUs), and cooling-related products. As the company's name suggests, their products are designed with quiet operation primarily in mind. The company is no stranger to the North American markets, slowly but steadily increasing their presence over the last few years. Their commitment to continue to increase their presence in the United States became apparent with the recent founding of a US-based service center at California for seamless after-sales support.

A quick look at the company's website hints that they are strongly, if not primarily, focused on the development and marketing of PSUs. Be Quiet! is currently offering over 30 different units that are divided into eight different series. In this review, we are taking a look at one of the company's most popular units, the Straight Power 11 750W PSU.

The Straight Power 11 series comprises six models, balanced between low-noise operation and high-power quality, all while trying to retain competitive price tags. Despite the designer's concept, the Straight Power 11 750W PSU currently retails for $140 plus shipping, a price that initially seems high for a unit that has an 80Plus Gold efficiency certification. The efficiency certification alone hardly says much about the overall performance and/or the quality of a PSU though, which we will thoroughly examine in this review.

Packaging and Bundle

We received the Straight Power 11 750W PSU in an aesthetically minimalistic but very sturdy cardboard box. Only a subtle image of the PSU itself stands out of the all-black front side of the box. Be Quiet! limits the text on the front of the box to the basic features of the unit, but plenty of details can be found on the sides and rear. The thick walls of the box and the polystyrene foam packaging provide ample protection during shipping.

The bundle of the Straight Power 11 750W PSU is basic, limited to just the necessary AC power cable, four black mounting screws, a few cable ties, and a simple user's manual. Two cable straps are also included and are holding together the two bundles of modular cables that come with the unit. The Straight Power 11 750W PSU is an all-modular design, meaning that every cable is detachable, including even the main 24-pin ATX cable. Every wire and connector is black but also every cable is a classic cable with black sleeving covering it. There are no "flat", ribbon-like cables supplies with the Straight Power 11.

At this point we should also mention that Be Quiet! is offering an "upgrade check" via their website, allowing users to check whether their older Be Quiet! PSU has cables compatible with this (or any other) new unit. The company is trying to retain at least partial compatibility between the cables of different PSU series, so it is relatively easy to switch from a smaller and/or older PSU to a new model, especially when cable management/routing is an extensive job.

The Be Quiet! Straight Power 11 750W PSU 

External Appearance

The Straight Power 11 750W PSU sports a relatively subtle all-black appearance but with several distinct features that distinguish it from a common ATX PSU. The most prominent differentiation is the bottom panel of the chassis, which is a separate part from the metallic chassis. This part is made mostly out of plastic, with parallel metallic wires serving as the fan's guard, and is designed so as to reduce aerodynamic noise via its funnel-shaped intake and low resistance air intake. The chassis measures 170 mm deep and is slightly longer than that of a standard ATX PSU, which should not be an issue with any modern ATX-compliant tower case but it will prevent the Straight Power 11 750W PSU from fitting inside compact case designs.

Be Quiet! embossed the company logo on the left side of the chassis, which is the side that will most likely be visible from a windowed side panel. The sticker with the unit's electrical specifications and certifications can be found on the right side of the chassis, while the top side is entirely clean. On the partially perforated rear side of the Straight Power 11 750W PSU we can see an AC cable receptacle and a small switch.

The front side of the Straight Power 11 750W PSU is filled with the connectors for the modular cables. Be Quiet! is using a straight 5-pin connector for the SATA/Molex cables and dual row 12-pin connectors for the PCIe and CPU 12V cables. Even though each group consists of physically identical connectors, users should be careful not to connect the cables randomly, and instead follow the suggestions in the manual. Because the Straight Power 11 PSU features multiple 12V current rails (or at least multiple overcurrent protection triggers), the PSU will shut down if the load is improperly balanced. Meanwhile the ATX cable connects to two connectors at the PSU's side, a large 20-pin connector and a second 8-pin connector. 

Internal Design

The fan beneath the fancy finger guard of the Straight Power 11 is one of Be Quiet!'s own SilentWings fans. It is a very high quality fan, featuring a fluid-dynamic bearing (FDB) engine and custom "ribbed" wings for the optimization of airflow and lower noise output. The maximum speed of 1800 RPM is high for an 135 mm fan, so hopefully it won't reach quite such a high speed during normal operation.

Be Quiet! employs several OEMs for the design and production of their PSUs. The OEM behind the creation of the Straight Power 11 PSU is FSP Group, a company known for their advanced and cost-effective designs. This particular platform does not match any of the company's reference designs that we have seen to this date, meaning that it probably is exclusive to Be Quiet! and their Straight Power 11 series. The sticker with the company's logo should be on the main transformer of the design but the unit obviously heated up a bit too much during our testing, as we found the sticker floating around inside the unit when we opened it up. That probably is why OEMs do not use stickers to brand/rebrand anything inside any electronic device that will potentially get hot during operation.

As advertised, there are (almost) no wires inside the Straight Power 11 750W PSU, as the main and secondary boards are all physically directly attached to each other. The only exception are two AC wires going from the partial input filter found at the back of the AC receptacle down to the main PCB. We found a textbook filtering stage with a total of four Y capacitors, two X capacitors, and two filtering inductors leading to a single input rectifying bridge attached to its own dedicated heatsink. The large filtering inductor and two Rubycon 420V/330μF capacitors are the passive components of the APFC circuit, while the larger heatsink near the edge of the main PCB holds the active components, three transistors and a diode.

Two MOSFETs are the active components of the LLC resonant half-bridge primary inversion stage. The secondary side MOSFETs that generate the single 12V line are placed on the underside of the PCB, with thermal pads assisting their cooling by transferring a portion of their thermal losses to the chassis. The two silver heatsinks that can be seen near the main transformer cover most of the cooling needs of the secondary side MOSFETs. The 3.3V and 5V lines are being generated “on-demand” via the DC-to-DC conversion circuits found on the large vertical PCB at the edge of the unit. Most of the secondary capacitors on the main PCB are electrolytic, a mix of Rubycon and Nippon Chemi-Con products, but there are a few Nichicon polymer capacitors on the main PCB as well. Nichicon supplies all of the polymer capacitors found on the main and secondary boards of this design.

Cold Test Results

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.

The efficiency of the Be Quiet! Straight Power 11 750W PSU is not going to break any records but it does meet the 80Plus Gold certification requirements. Across the nominal load range (20% to 100% of the unit's capacity), the average efficiency of the Straight Power 11 750W PSU is 91.9% and 90.2% with an input voltage of 230V and 115V respectively. Where the Straight Power 11 fails to impress is under very low loads, with the efficiency diving below 75% when the load is lower than about 40 Watts.

The Be Quiet! Straight Power 11 750W PSU displays exceptional thermal performance, maintaining comparatively low internal temperatures considering its efficiency rating, class, and components. By looking at the air temperature graph we can surmise that the PSU does a great job handling its thermal losses with excellent heat dissipation capabilities.

Although the Straight Power 11 750W PSU lacks any advanced form of fan speed control, the unit is virtually inaudible while the load is low. However, the speed of the 135 mm fan continually increases alongside with the load and its noise will be noticeable as soon as the load is close to or greater than 350 Watts. Beyond that point, the speed of the fan will increase even more sharply and will reach borderline uncomfortable levels when the PSU’s load is greater than 650 Watts.

Hot Test Results

The electrical performance of the Straight Power 11 750W PSU is good, yet perhaps unimpressive considering the premium character of the product. Voltage regulation is good, at about 1.5% for the 12V and 5V lines and at 2.6% for the 3.3V line. Line filtering is good as well, with our instruments recording a maximum of 36 mV, 24 mV, and 24 mV on the 12V, 5V, and 3.3V lines respectively (with balanced loading), figures that are very well within the design guide limits.

The Straight Power 11 750W PSU experiences a significant efficiency drop when the ambient temperature is very high. This drop is almost evenly distributed across the load range, suggesting that the components are not getting thermally stressed. Even so, the average efficiency reduction is 2.7%, with a substantial drop of 4.3% at 100% load. We should note that the 80Plus certification tests take place at room temperature and not under such adverse ambient conditions.

Even though the unit’s efficiency takes a substantial hit when the ambient temperature is high, the internal temperatures of the PSU are very low. Our instruments recorded temperatures just above 75 degrees with the unit operating at maximum capacity, when the majority of other designs lands close to 90 degrees. It is not clear why the designers of this PSU chose to have this much headroom, especially with a unit primarily designed with quiet operation in mind, but such low internal temperatures will certainly aid with the longevity of the PSU.

Expectedly, the fan’s cooling profile is much more aggressive now that the ambient temperature is very high, which is the culprit behind the exceptional thermal performance of the Straight Power 11 750W PSU. The obvious shortcoming of this approach is that the fan is audible even when the PSU is lightly loaded, while it reaches uncomfortable noise levels once the load surpasses 350-400 Watts. Considering that quiet operation is the major selling point of this PSU, its thermal design surely is peculiar.

Conclusion

Be Quiet's Straight Power 11 is a unit designed to provide premium quality and performance to advanced users. It stands but a step lower than the company's top-tier series, the Dark Power Pro, which bears a higher efficiency certification. On paper, the Straight Power 11 is an impressive product, with impressive quality and performance specifications. It is also worthwhile to note that this is one of the very few premier PSUs that features multiple 12V rails. Whether the presence of multiple rails is a good thing or not is a topic for debate – multiple rails are safer, as the protection circuitry will not allow a single cable or connector to draw the entirety of the unit’s power output and be damaged. But on the other hand, balancing the load between the rails is necessary and certain devices that require very high currents may even be unusable with such a PSU.

Aesthetically, the Straight Power 11 is very subtle but does stand out a little, mostly due to its proprietary fan finger guard. Other than that, the designers did the best they could to make the PSU aesthetically pleasing without drawing unnecessary attention, keeping stickers out of sight and painting literally everything black. At least some of the cables, which are the most difficult part to conceal when building a PC, could be replaced by ribbon-like cables that are thinner and more flexible than sleeved cables, yet the designer opted for uniformity and added sleeving to every single cable of the PSU.

In terms of electrical performance, the Straight Power 11 PSU does perform very well overall. Its power output quality is very good, with our instruments showing well-regulated, stable voltage lines and good voltage ripple/noise filtering. The unit does honor its 80Plus Gold efficiency certification, easily meeting the energy conversion efficiency requirements regardless of the load. Our only complaint is that the very low load efficiency of the Straight Power 11 750W PSU is poor. This does not affect the unit’s efficiency certification because the significant efficiency drop happens below the nominal load range but, as systems are becoming more and more energy efficient in general as laptop-like power management techniques make their way to desktops, it is likely to significantly affect the overall energy consumption of newer and future computers.

Meanwhile when it comes to noise, it's worth noting that Be Quiet! is a company that primarily designs and markets products for low noise output. Which in the case of the Straight Power 11 series makes it difficult for us to give it a positive evaluation. The 750W unit that we reviewed is indeed relatively quiet under normal operating conditions, but that can change very quickly when the unit is heavily loaded or if the ambient temperature is high. Although the very aggressive thermal profile of the Straight Power 11 maintains very low operating temperatures that will surely improve the longevity of the PSU, it also places the Straight Power 11 behind the competition when it comes to acoustics, which does not bode well for a product that low noise operation is the basis of its entire marketing plan. In particular, the fact that the fan speed is load-driven rather than temperature-driven would seem to be to the PSU's detriment.

The Straight Power 11 PSU series stands at a peculiar place in the market, with Be Quiet! marketing it as a premium series, yet next to their actual premium series, the Dark Power Pro. The overall performance of the Straight Power 11 750W PSU that we reviewed today is by all means a good PSU, yet incapable of competing with the equally priced offerings of other manufacturers. Given that it's an 80Plus Gold-certified PSU, and considering its overall performance, the Straight Power 11 750W PSU should be retailing for less than $100 in order to remain competitive.