Sennheiser HD 820 – Over Ear Closed Back Wired Headphones

Sennheiser HD 820 – Over Ear Closed Back Wired Headphones

The Sennheiser HD 820 opens up new tonal horizons, combining the transparency and naturalness of the best open-back headphones with the isolation and serenity of a closed-back design. Its patent-pending acoustic diffraction housing uses convex Gorilla Glass panes to direct rear-radiated sound waves into ring-shaped absorber elements, delivering clear, interference-free, spatial reproduction across the full frequency spectrum. Developed in Germany and handcrafted in Ireland, the HD 820 sets a new benchmark for closed-back headphones.

• Wired, over-ear, closed-back dynamic reference headphone
• 56 mm Ring Radiator transducer
• Frequency response: 6 – 48,000 Hz (–10 dB)
• Impedance: 300 Ω
• Two included detachable cables (3 m each): 6.35 mm unbalanced and 4.4 mm balanced, both gold-plated; optional XLR-4 balanced cable available (Sennheiser CH 800 S)
• Weight: 360 g (without cable)
• Developed in Germany, handcrafted in Ireland
• 2 Year Warranty

Highlights & Key Technologies

Acoustic Diffraction Housing with Gorilla Glass
The defining innovation of the HD 820 is its patent-pending acoustic diffraction housing, recognizable by the two convex glass panes behind the transducers. Made from extremely stiff Gorilla Glass and shaped using a specially developed process, these concave reflectors direct the sound radiated from the rear of the diaphragm into dampened chambers. The ring-shaped absorber elements located around the transducers capture reflected sound waves in a controlled manner, preventing them from disturbing the transducer movement or compromising reproduction accuracy. The pressure and speed of the sound waves remain controllable at all times, resulting in clear, interference-free, spatial sound reproduction across the entire frequency spectrum — from approximately 6 Hz to 48,000 Hz. The glass panes also provide a visible window into the headphone's internal transducer architecture. Handle with care: do not drop the headphones, as shattered glass can cause injury, and allow at least 2 hours of acclimatization when moving from cold to warm environments to prevent condensation on the glass panes.

56 mm Ring Radiator Transducer
The HD 820 uses a 56 mm Ring Radiator transducer — the largest ever used in a dynamic headphone. Rather than a single attachment on the outer circumference, both outer and inner edges of the ring-shaped diaphragm are secured to the drive unit, leveraging the air displacement advantages of a large diaphragm while maintaining the rigidity that favorably impacts rest and response times. The voice coil vibrates the diaphragm, connected to the V-shaped groove found near the center of the ring. Each transducer is manufactured, tested, and measured to an extremely tight tolerance to ensure dependable performance out of the box. Each HD 820 is delivered with a signed chart providing its individually measured frequency response curve and serial number.

Vibration Damping & Chassis
The headphone's vibration-damping chassis and inert headband insert provide complete stability, resulting in astonishing speed and accuracy throughout the entire frequency spectrum. The double-shell housing construction is extremely lightweight and stiff. The headphone yokes are the result of complex mechanical strength simulations and field tests, guaranteeing a lasting, comfortable fit. Aerospace-grade materials are used throughout for high strength with minimal weight. The drivers are angled to allow precise localization of voices, instruments, and their inherent environments.

Cable & Connectivity
The HD 820 ships with two silver-plated, oxygen-free copper (OFC) cables, both 3 meters in length, balanced construction, shielded, and reinforced with para-aramid fibers. One terminates in a gold-plated 1/4" (6.35 mm) stereo jack plug (unbalanced, 3-pin) and the other in a gold-plated 4.4 mm stereo jack plug (balanced, 5-pin). Both cables are impedance-matched with ultra-low capacitance and use high-precision ODU connectors at the headphone end. An optional XLR-4 balanced cable (Sennheiser CH 800 S, 4-pin) is available as an accessory. The 6.35 mm connector can also be connected to a 3.5 mm stereo jack socket using a standard adapter (not included). The HD 820 is recommended for use with headphone amplifiers such as the Sennheiser HDV 820.

Comfort & Construction
The HD 820 features an ultra-ergonomic design with an adjustable metal headband and dual-axis articulating ear cups that instantly and effortlessly conform to the wearer's head structure. All contact points use ultra-soft microfiber padding, including the handcrafted ear pads and headband cushion. The ear pads, internal 3D mesh dust protectors, and headband padding are all user-replaceable. The dust protectors can be washed under lukewarm water and air dried. The luxurious ear padding and progressive articulation points form a satisfying seal, eliminating distractions and preventing unwanted sound from entering or bleeding out during extended listening sessions. The HD 820 is developed in Germany and handcrafted in Sennheiser's state-of-the-art Ireland plant. A storage box and microfiber cloth are included.

Details & Specifications

MODEL INFORMATION
Model: HD 820
Article number (SKU): 507435

TRANSDUCER
Transducer principle: Dynamic, closed-back
Transducer type: 56 mm Ring Radiator
Ear coupling: Circumaural
Frequency characteristic: Diffuse-field equalized
Maximum value of the static magnetic field at the surface: 10.5 mT

PERFORMANCE
Frequency response: 12 – 43,800 Hz (–3 dB); 6 – 48,000 Hz (–10 dB)
Nominal impedance: 300 Ω
Sound pressure level at 1 kHz: 103 dB (1 Vrms)
Total harmonic distortion: ≤ 0.02% (1 kHz, 100 dB SPL)
Long-term input power: Max 500 mW (per EN 60268-7)
Attenuation: Up to 25 dB

CABLE & CONNECTIVITY
Connection cables: Silver-plated, oxygen-free copper cable (OFC), balanced, shielded, para-aramid reinforced, 3 m
Connectors (gold-plated): XLR-4, balanced, 4-pin; Stereo jack plug: 1/4" (6.35 mm), unbalanced, 3-pin; 4.4 mm, balanced, 5-pin
Headphone connector: High-precision ODU connectors
Optional balanced cable: XLR-4 (Sennheiser CH 800 S)

PHYSICAL SPECIFICATIONS
Weight: Approximately 360 g (without connection cable)
Contact pressure: Approximately 3.8 N ± 0.3 N
Ear cup housing: Patent-pending acoustic diffraction housing with convex Gorilla Glass panes
Ear pads: Handcrafted microfiber, user-replaceable
Headband padding: Microfiber, user-replaceable
Dust protectors: 3D mesh, washable and replaceable

ENVIRONMENTAL
Operating temperature: –10°C to +55°C
Storage temperature: –20°C to +70°C
Operating relative humidity: 10% to 80% (non-condensing)
Storage relative humidity: 10% to 90% (non-condensing)

INCLUDED ACCESSORIES
HD 820 closed-back, dynamic headphones
Connection cable with 1/4" (6.35 mm) stereo jack plug, unbalanced (pre-connected)
Connection cable with 4.4 mm stereo jack plug, balanced
Instruction manual
Storage box
Microfiber cloth