be quiet! Dark Base 900 Midi Tower Black, Silver

£191.80 (£159.83 + VAT)

be quiet! Dark Base 900. Form factor: Midi Tower, Type: PC, Product colour: Black, Silver. Supported power supply form factors: ATX. Front fans installed: 2x 140 mm, Front fans diameters supported: 120,140 mm, Side fans diameters supported: 120 mm. Supported HDD sizes: 2.5,3.5″. Width: 243 mm, Depth: 577 mm, Height: 585 mm

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SKU: BG012 Category:

Product Information

Outstanding Flexibility and Silence

be quiet! Dark Base 900: unrivaled flexibility with impeccable cooling and silence features. It was designed for high-end enthusiasts and individualists – all of those who expect the highest standards when it comes to modularity, compatibility and design for their high-end workstations as well as overclocked and silent water-cooled systems. 

Dark Base 900 has numerous modularity options to satisfy every desire with lots of features to support special configurations. Aluminum surfaces and steel offer highest stability with a look of extreme elegance. Simply an engineering work of art!
  • Fully versatile thanks to modular construction, offering an relocatable motherboard tray, repositionable HDD slots, support for even E-ATX and XL-ATX as well as the possibility of an inverse layout
  • Three pre-installed SilentWings® 3 140mm PWM fans featuring a smooth-running 6-pole motor, fluid-dynamic bearing and funnel-shaped air inlets
  • Effective full circuit airflow system with innovative noise-reducing vents all around the case
  • Completely sound insulated case with decoupled elements for motherboard, power supply and drives
  • Four areas for water cooling radiators up to 420mm on top, front, back and base of the case
  • 2-in-1 side panel vent can be closed for silent operation or opened for two additional fans
  • Product conception, design and quality control in Germany


• High-end workstations and desktop PCs
• High-resolution gaming and multimedia systems
• Extremely overclocked systems
• Super silent water-cooled PCs


Unrivaled Flexibility

• Motherboard tray with enhanced possibilities to suit individual space requirements
   – Completely relocatable and usable as a test bench
   – Adjustable to three different heights
   – Installation alongside the left panel for an inverted layout
• Repositionable HDD tray for individual space requirements inside the case
• E-ATX and XL-ATX support permits installation of practically any motherboard
• Installation options of up to 7 decoupled HDDs, 15 SSDs and 2 optical drives
Impeccable Cooling and Silence

• Three virtually inaudible SilentWings® 3 140mm PWM fans offer unrivaled and uncompromising performance with a broad range of amazing features:
   – 6-pole fan motor for very low power consumption and less vibration
   – Fluid-dynamic bearing with copper core enables a super long life span
   – Unique airflow-optimized fan blade design
   – Fan frame with funnel-shaped air inlets produces high air pressure
   – High quality IC motor controller reduces electrical noise
• Intelligent full circuit airflow system with noise-dampened vents all around the case
• Manual stepless fan controller supports up to three PWM and three 3-pin fans
• Installation of up to six additional 140mm fans or up to nine additional 120mm fans possible
• Ready for water cooling radiators up to 420mm with four mounting slots:
   – Front: 420mm – Top: 420mm – Back: 140mm – Base: 280mm
• Built-in insulation in front, top cover and side panels
• Decoupled motherboard tray, power supply tray and drive slots for reduced vibration and noise
• 2-in-1 side panel vent can be closed for silent operation or opened with the possibility to mount two additional 120mm fans

Advanced Assembly and Handling

• Generous space thanks to repositionable single HDD slots
• Impressive features permit individual configurations and setups
• Customizable cable management thanks to carefully placed pass-throughs
• Two cleanable dust filters that can be conveniently removed from the front
High-quality Materials and Elegant Design

• Premium aluminum surfaces
• Steel parts from 0.8mm to 1.0mm for highest stability
• Compatibility with all be quiet! products and all available graphics cards
Outstanding Service and Support

• 3-year manufacturer's warranty
• Quick support is available via our international hotline, Mondays to Fridays from 9:00am to 5:30pm CET: 
+49 (0) 40-736 76 86 – 98


Supported motherboard form factors



Package width

325 mm

Rear radiator fan sizes supported

120,140 mm

Number of side fans supported (max)


Number of top fans supported (max)


USB 2.0 ports quantity


Top fans diameters supported

120,140,180 mm

Audio input


Maximum graphics card length

47 cm

Side window



ABS synthetics, Aluminium, Steel

Rear fans installed

1x 140 mm

Package depth

655 mm

Product colour

Black, Silver

Maximum CPU cooler height

18.5 cm

Supported HDD sizes


Fan speed


Number of 5.25" bays


Front fans installed

2x 140 mm

Number of 2.5" bays


Power supply included


Number of front fans supported (max)


Front radiator fan sizes supported

120,140,240,280,360,420 mm



Bottom fans diameters supported

120,140 mm

USB 3.2 Gen 1 (3.1 Gen 1) Type-A ports quantity


Liquid cooling capability


Side fans diameters supported

120 mm

Package height

680 mm

Audio output


Form factor

Midi Tower

Maximum PSU length

18.4 cm

Number of 3.5" bays


Front fans diameters supported

120,140 mm

Anti-dust filter


Number of bottom fans supported (max)


Supported power supply form factors


Top radiator fan sizes supported

120,140,240,280,360,420 mm

Package weight

16.3 kg

Number of expansion slots






Form Factor


Power Supply Wattage


Motherboard Support


Connectors / Controls

2 x USB 3.0
2 x USB 2.0
HD Audio (mic & headphone jacks)

Drive Bays

2 x 5.25" (removable)
7 x 3.5" (individually removable)
1 x 2.5" on motherboard tray
14 x 2.5" inside HDD slots (removable)

Expansion Slots

8 x Expansion Slots

Cooling System

2 x front 14cm Pure Wing 2 Fans
1 x rear 14cm Pure Wing 2 Fan

Optional fans (mm):
Top: 3x 140 / 4x 120 / 1x 180
Front: 1x 140, 120 (w/o ODD cage)
Bottom: 2x 140, 120
Side panel: 2x 120


Black and Silver


VGA card:
w/o HDD slots: 470 mm

Max CPU cooler length: up to 185 mm

without bottom fan: 150 – 184 mm

Additional Features

See More Information


14.2 kg
(L x W x H) 577 x 243 x 585 mm


3 Years