be quiet! Straight Power 11 850W PSU Review & Giveaway

Quiet, well behaved, but expensive.

It's a giveaway! PC Perspective has teamed up with be quiet! to give away three of the Straight Power 11 850W power supplies reviewed here by Lee. See rules and entry details at the bottom of the review.

Introduction & Features

be quiet! claims to be the number one PSU manufacturer in Germany and they are continually working to expand their presence in North American as well. The be quiet! Straight Power 11 series sits just below the company’s high-end Dark Power Pro 11 series and includes six models: 450W, 550W, 650W, 750W, 850W, and 1000W. All of the Straight Power 11 models are certified for high efficiency (80 Plus Gold) and come with modular cables. We will be taking a detailed look at the Straight Power 11 850W power supply in this review.

As you might expect, be quiet! is focused on delivering virtually silent power supplies. be quiet! designed the Straight Power 11 Series to provide reliable operation with minimal noise for systems that demand extremely quiet operation. To accomplish this, be quiet! uses one of their own high-quality Silent Wings 3 fans that features ribbed fan blades and a Fluid Dynamic Bearing (FDB). The power supply also uses a unique fan guard and funnel-shaped fan opening to help maximize airflow and reduce noise.

All of the Straight Power 11 Series power supplies are fully-modular for maximum build flexibility and incorporate sleeved cables. In addition to the Straight Power 11 Series, be quiet! offers a full range of power supplies in ATX, SFX, and TFX form factors.

be quiet! Straight Power 11 850W PSU Key Features:

  • 850W continuous DC output (ATX12V v2.4, EPS 2.92 compliant)
  • Virtually inaudible Silent Wings 3 135mm FDB cooling fan
  • 80 PLUS Gold certified efficiency (up to 93%)
  • Japanese 105°C rated capacitors ensure stability and reliability
  • Wire-free design on the DC side for enhanced cooling and longevity
  • User-friendly cable management reduces clutter and improves airflow
  • Four high-performance 12V rails
  • Advanced topology incorporating LLC, SR and DC-to-DC design
  • Powerful GPU support with four 6+2 pin PCI-E connectors
  • ErP and Energy Star 6.1 ready
  • Active Power Factor correction (0.99) with Universal AC input
  • Safety Protections: OCP, OVP, UVP, SCP, OPP, and OTP
  • 5-Year warranty
  • Product conception, design and quality control in Germany
  • $169.99 USD (, March 2019)

Here is what be quiet! has to say about the Straight Power 11 850W PSU:

be quiet! Straight Power 11 850W raises the bar for systems that demand virtually inaudible operation without power quality compromises. Straight Power 11 850W is certified with 80 PLUS Gold efficiency, reaching up to 93%. This gives less power consumption and a cooler and quieter operation. Truly a benefit for any system.

The high-end Silent Wings 3 fan delivers best-of-class airflow yet produces very little noise. This is thanks to its unique, optimized fan blade design along with an advanced fluid-dynamic bearing and 6-pole fan motor that largely eliminates operational noise, has a super-long life and minimal power consumption. The fan inlet of the Straight Power 11 850W is funnel-shaped. It causes an increased throughput of air which benefits to a higher cooling performance.

An absolute innovation: The Straight Power 11 850W is wire-free on the DC side inside the PSU body. This results in improved cooling airflow and less signal disturbance, simply because of a lack of wiring, and ultimately pushes the lifetimes of the components to a maximum. Thanks to the fully modular cable management, cables that serve no purpose in the system are left out. For this reason systems always appear very tidy. At the same time installation is performed much more conveniently. A smoother airflow results from the uncluttered layout of the system, which means lower noise and temperatures prevail inside the case.

The use of LLC and Synchronous Rectifier (SR) provides very stable operation and enhanced voltage regulation. The PSU is equipped with DC-to-DC conversion for tight voltage regulation even under heavy cross-loading conditions. This ensures reliable operation with the next generation of processors and graphics cards. Only the best components are used in Straight Power 11 850W. That is why we have built only high-quality Japanese capacitors into the PSU chassis. They are rated to 105°C, ensuring stability, reliability and a long operating life.

Specifications & Packaging


(Courtesy of be quiet!)

The be quiet! Straight Power 11 850W power supply is rated for a combined, continuous output power of up to 850 watts at 40°C operating temperature. The PSU incorporates four independent +12V rails, which can deliver up to 70.8A (849.6W) on the combined +12V outputs (see table below for rail distribution). The PSU includes universal AC line input (automatically adjusts the AC line voltage) and active PFC, which makes the unit more environmentally friendly to the local power grid. 

Straight Power 11 850W PSU Specifications (from the be quiet! website):

Packaging & Parts

The Straight Power 11 850W power supply was delivered to us from (no hand-picked units for review here). The power supply arrived securely packed inside a standard retail box highlighting the unit’s main features and specifications.

The power supply is wrapped in plastic and protected by a cardboard insert. All the modular cables and accessories are packed under the cardboard flaps. In addition to the power supply, the box contains a power cord, two bundles of modular cables, mounting screws, wire ties, Velcro cable wraps, and a multi-language User Manual.

Modular PCI-E and CPU power cables

Modular peripheral cables and FDD adapter

(Courtesy of be quiet!)

A Detailed Look

The be quiet! Straight Power 11 850W power supply enclosure is painted matte black and measures 170mm (6.7”) long. The back panel includes an On-Off switch, AC receptacle and honey-comb grill area for exhaust airflow. The large intake fan grill is made up of multiple parallel bars for minimal restriction and good airflow.

The power supply uses a 135mm Silent Wings 3 fan for cooling (BQ SIW3-13525-HF) that incorporates a fluid dynamic bearing (FDB) for quiet operation and long, reliable life. The sculpted fan blades are designed to reduce air turbulence and noise. The fan is rated for 0.56A and 2100 rpm at 12 VDC. The 6-pole fan motor and IC motor control circuit produce smooth low-speed operation and reduced noise for exceptionally quiet operation.

The front panel includes eleven connectors for the modular cables, all nicely keyed and labeled.

The Straight Power 11 power supply comes with a good assortment of ten fully modular cables for easy installation and clean builds. All of the cables are covered with black plastic mesh sleeving.

Here are a few pictures showing the layout and components inside the be quiet! Straight Power 11 850W power supply.  be quiet! appears to be using FSP Group as their OEM partner for the Straight Power 11 Series. The layout and build quality both appear very good. Notice the lack of wires which is evidence of the wire-free design on the DC side that be quiet! is promoting for these PSUs.

FSP is using a modern, high-performance half-bridge LLC, Synchronous Rectification power conversion design along with DC-to-DC voltage regulators located on a daughter card to provide good voltage regulation and high efficiency.

All of the Japanese made capacitors are rated for 105°C operation and the two electrolytic bulk caps are made by Rubycon: (1) 470 uF, 420V, 105°C and (1) 330 uF, 420V, 105°C.

DC Load Regulation & AC Ripple

PSU Testing Methodology

Establishing an accurate load is critical to testing and evaluating a PC power supply.  PC Perspective’s power supply test bench can place a precise DC load on the PSU under test.  Each power supply is tested under controlled, demanding conditions up to its maximum rated load (at 40ºC). Our current suite of tests includes:

  • DC Load Regulation
  • AC Ripple and Noise
  • Efficiency
  • Differential Temperature
  • Noise

The be quiet! Straight Power 11 850W power supply was evaluated on both features and performance.  A full range of equipment was used to test the power supply under controlled load conditions. 

  • (2) CSI3710A Programmable DC load (+3.3V and +5V outputs)
  • (4) CSI3711A Programmable DC load (+12V)
  • (3) 218W Precision resistor load bank (+12V)
  • Switchable precision resistor load bank (-12V and +5VSB)
  • Agilent 34401A digital multimeter (Accuracy ±0.0035% vDC)
  • Extech 380803 Power Analyzer (Accuracy ±0.5% of full scale)
  • DS1M12 "StingRay" digital oscilloscope (20M S/s with 12 Bit ADC)
  • Powerstat Variable Autotransformer, 1.4 KVA, 0-140 VAC
  • Extech Model 407738 digital sound level meter (Accuracy ±1.5 dB)

The following cables/connectors were used to connect the Straight Power 11 850W power supply to the PCPerspective power supply test equipment.

  • (1) 20+4 pin ATX
  • (2) 8-pin EPS/ATX12V
  • (4) 6-pin PCI-E
  • (6) SATA
  • (3) Molex

DC Output Load Regulation

To simulate demanding and maximum loading conditions, the be quiet! Straight Power 11 850W power supply was connected to the load testers and supplied with a constant 120 VAC.  In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads. 

The ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances now for the +12V outputs.  I have also included a second table of expanded tolerances (±1% to ±6%) for reference.

The following tables list the DC voltage results for the PSU while operating on 120 VAC, 60 Hz.

The Straight Power 11 850W power supply produced very good voltage regulation on all of the DC outputs all the way up to 850 watts total load. All of the primary rails stayed within ±2%. We are off to a good start.

AC Ripple & Noise on the DC Outputs

The amount of AC ripple and noise present on the DC outputs was checked using a digital oscilloscope.  This AC component may be present in the KHz range where most switching power supplies operate or it may be more prevalent at the 60 Hz line frequency. We adjust the O-scope time base to look for AC ripple at both low and high frequencies.  The ATX12V V2.2 specification for DC output noise/ripple is defined in the ATX12V Power Supply Design Guide.

Ideally we would like to see no AC ripple (repetitive) or noise (random) on the DC outputs – the cleaner the better!  But in reality there will always be some present. I measured the amplitude of the AC signal (in millivolts, peak-to-peak) to see how well the power supply complied with the ATX standard. The following table lists the ripple/noise results during all of the load tests for the main output voltages of interest.

The Straight Power 11 850W power supply held AC ripple and noise well in check across the full range of loads. Overall, very good and well below the ATX recommended guidelines.

Efficiency, Differential Temperature, and Noise


Efficiency is defined by the power output divided by the power input and is usually expressed as a percentage.  If a PSU were a 100% efficient (which none are) 850 watts of AC power going in would result in 850 watts of DC power coming out (with no waste heat to dissipate).  In the real world there are always inefficiencies and power is lost in the form of heat during the conversion process. Newer revisions to the ATX12V Power Supply Design Guide V 2.2 have continued to increase the efficiency recommendations for PC switching mode power supplies and now lists both required and recommended minimum efficiencies.

We measured the AC power input to the Straight Power 11 850W PSU with an Extech power analyzer while the total DC load was found by adding all the individual +3.3V, +5V, +12V, -12V and +5VSB loads together.

The overall efficiency of the Straight Power 11 850W power supply is very good and easily meets the criteria for 80 Plus Gold certification, even while operating on 120 VAC and at elevated temperatures.

80 Plus Program

Note: Tests conducted at room temperature (25°C)

Differential Temperature & Noise Levels

To simulate a demanding environment, some of the warm exhaust air from the PSU under test is recirculated back to the intake through a passive air duct, which allows the PSU air inlet temperature to increase with load, just like it would in a real PC.

The differential temperature across the power supply was calculated by subtracting the internal case air temperature (T in) from the temperature of the warm exhaust air flowing out the back of the power supply (T out).

Thermocouples were placed at the air inlet and exhaust outlet. The ambient room air temperature was 23ºC (74ºF) +/- 0.5ºC during testing.

T out = temperature of air exhausting from power supply
T in = temperature of air entering power supply
Delta T = T out – T in

Sound pressure level readings were taken 3’ away from the rear of the case in an otherwise quiet room.  The ambient noise level was ~27 dBA.

The Straight Power 11 850W power supply started out very quiet – virtually silent up through mid-power. As the power supply approaches full output the fan ramps up quickly and at the 850W mark the fan noise was very noticeable. I was not able to take a SPL reading at the 850W load mark due to all the programmable DC load cooling fans running constantly.

(Courtesy of be quiet!)

Final Thoughts & Conclusions

The Straight Power 11 Series is currently close to the top of be quiet!’s premium product offering and includes six models ranging from 450W up to 1000W. The 850W model we tested delivered very good electrical performance and stayed quiet well through mid-load.

The Straight Power 11 850W PSU produced very good voltage regulation (±2%) with low AC ripple and noise on the DC outputs.  Efficiency was also very good and easily met the requirements for 80 Plus Gold certification, which along with be quiet!’s 135mm Silent Wings 3 fan resulted in virtually silent operation at low to mid power levels. The Straight Power 11 850W PSU comes with a good bundle of all modular cables, all of which are sleeved for easy installation.

While the overall component selection and electrical performance were very good across the board, we were a bit disappointed to see the power supply only rated for a max 40°C operating temperature and backed by only a 5-year warranty. Most premium PSUs are rated for up to 50°C and come with at least a 10-years warranty). In our opinion the max operating temperature and warranty period are good indicators of how confident a manufacturer is in their product and it seems to us that, considering the Straight Power 11's performance and quality, it deserves better.

The Straight Power 11 850W power supply is currently available and selling for between $160 and $170 USD ($169 – Newegg / $162 – Amazon), which makes this unit slightly expensive for an 80 Plus Gold PSU compared to the competition (Seasonic, EVGA, Corsair, etc.).


  • Quiet operation, virtually silent at low to mid-power levels
  • 80 PLUS Gold certified (90~93% efficiency at 20-100% load)
  • Very good voltage regulation (±2%) with low AC ripple and noise
  • High-quality components: FDB fan and Japanese 105°C capacitors
  • Fully modular, sleeved cable set
  • Active Power Factor correction (0.99) with Universal AC input
  • Safety Protections : OCP, OVP, UVP, SCP, OPP, and OTP
  • Available in: 450W, 550W, 650W, 750W, 850W, 1000W


  • 5-Year warranty and 40°C max operating temp lag some competitors
  • Expensive compared to other premium grade 850W Gold PSUs


We've partnered with be quiet! to give away three Straight Power 11 850W PSUs. Check out the contest widget below for details on how to enter and win! The contest is open until 11:59PM EDT on Friday, April 19th. Update: due to our lack of a podcast last week, we have extended the contest until 11:59 PM EDT on Tuesday, April 23rd. Three winners will be chosen to each receive one Straight Power 11 850W.

be quiet! Straight Power 11 850W PSU Giveaway

Due to shipping requirements, we can unfortunately only ship to winners who provide U.S. addresses. Thanks to be quiet! for providing the review and giveaway units of the Straight Power 11!