Features

Audioengine HD4 Powered Speakers: The Audioengine's HD4's speaker cabinets, drivers, innovative bass port design, amplifier, and passive crossover network are critically tuned together, providing a more efficient system requiring less power than passive speakers & external amplifiers. The HD4 is not a "box-built" system with off-the-shelf parts, but includes custom-designed components constructed to Audioengine's specifications for high quality, high performance sound.

Two-Way Driver Design: The Audioengine HD4 employs a two-way driver design. Each speaker is outfitted with a 0.75" silk dome tweeter and a 4" aramid fiber cone woofer for a wide stereo soundstage.

• Silk Dome Tweeter: The HD4 uses an audiophile-quality, ferrofluid-cooled silk dome tweeter with a neodymium magnet. Silk tweeters hold up well under high power and the edge-driven design gives very smooth response.
• Aramid Fiber Woofer: The Aramid fiber cone woofer is very rigid and stiff, responds quickly to vibration, and reproduces voice coil vibrations accurately. The Aramid fiber woofer has a broad and smooth midrange with satisfying low end response. The rigidity of the material provides tight control over the sound vibrations, and projects well for room-filling sound.

Built-In Amplifier: The 60W amplifier in the Audioengine HD4 is located in the left speaker and is a conservatively-rated dual class A/B analog monoblock design. This is a more traditional speaker/amplifier configuration which provides excellent quality audio and greater flexibility. All circuit boards for the power and preamp sections are vertically mounted for maximum mechanical shock protection. The built-in power amplifier saves space & eliminates the need to connect Audioengine HD4 to a stereo receiver or external power amp. The included 6.5' speaker wire connects from the left speaker's binding-post terminals to the right speaker's binding post terminals to power the right speaker.

Hand-Built Cabinets: The Audioengine HD4's speaker cabinets are hand-built with furniture-grade finishes. The HD4 cabinets are available in several handsome finishes, including walnut and cherry veneers as well as satin black and white paint; offering a wide choice for complementing room furnishings. Also included are detachable grills that add further aesthetic advantages as they are firmly held in place with hidden neodymium magnets for a clean look.

Front-Slot Port: One of the reasons the Audioengine HD4 has such great bass response for a compact speaker is its slot-ported cabinet. Each cabinet features a front-firing slot-port that has been specifically tuned for accurate bass down to 60Hz. The result is low end with minimal audible air turbulence, so you can use the Audioengine HD4 speakers with or without a separate subwoofer.

24-bit Upsampling DAC: The HD4's built-in Bluetooth receiver and USB input both utilize the AKM AK4396A DAC, widely known for its low-noise and high-fidelity. The AK4396A is used as an upsampling DAC and will pad all bit depths to 24-bits, achieving a higher signal-to-noise ratio and lower noise floor. Due to the high signal-to-noise specs of the AK4396A, the fact that digital signal is upsampled to 24-bits, as well as the added benefit of onboard triple redundancy power source conversion and filtering, the HD4 Bluetooth implementation presents impressive low noise and low distortion characteristics with a noticeable improvement over many other Bluetooth devices.

Bluetooth Music Streaming The Audioengine HD4 incorporates built-in Bluetooth 5.0 for wireless music streaming of stored music and music apps on your Bluetooth-enabled Apple iPod/iPhone/iPad, Android smartphone/tablet, Windows PC/Phone, Mac computer/laptop, and more to the powered speaker system. You will continue to control your music and view song/artist information from your Bluetooth-enabled device.

• aptX-HD Compatible:In addition to support for Bluetooth's standard SBC audio codec, the Audioengine speaker supports AAC for higher quality playback from Apple iOS devices, as well as support of aptX HD for 24-bit/48kHz audio playback from compatible devices. aptX HD supports 48kHz/24-bit LPCM audio over a Bluetooth wireless connection for a "better-than-CD" listening experience.
• 100' Wireless Range: Most Bluetooth products have very limited range (only up to 30'), typically within just one room. But with careful signal management circuitry and antenna tuning, the HD4 offers a superior solution that has up to 3x the range (up to 100') of standard Bluetooth for multiroom use, with no degradation in audio quality.

microUSB Input: The Audioengine HD4 is fitted with a microUSB input that can be used to playback music files from your Windows PC or Mac computer (no separate USB driver necessary). Simply use the included microUSB-to-USB cable to connect the HD4 to a free USB port on your computer. The microUSB input bypasses your computer's built-in low-quality DAC and utilizes the HD'3 24-bit upsampling DAC for a high-end listening experience. The Audioengine HD4's microUSB port supports music files up to 24-bit/44.1kHz or 48kHz.

Audiophile-Quality Headphone Amp: The Audioengine HD4 features an audiophile-quality, dedicated headphone amplifier with front-panel 3.5mm headphone output. The HD4's high-performance headphone amplifier is based on the OPA2134 low-noise opamp. This amp is able to provide low-impedance, high-fidelity audio and a 2-volt output which easily drives a wide range of headphones

Dual Aux Inputs: The HD4 is equipped with two analog Aux inputs. There is a stereo minijack (3.5mm) input and a stereo RCA input for connecting analog audio devices.

Variable Audio Output: The Audioengine HD4 includes a variable stereo preamp audio output so you can connect a powered subwoofer (such as the Audioengine S8; sold separately), other Audioengine powered speakers, or an Audioengine wireless adapter (772W3; sold separately) to daisy-chaining music to other systems around the house. This output is variable (adjustable) so the volume level can be controlled from the HD4.

Front-Panel Rotary Knob: The HD4's front-panel rotary knob allows you to turn the speaker system on or off, as well as adjust the volume level up or down.

Power Requirements: The Audioengine HD4's left speaker plugs into an AC power outlet using the included 6' detachable AC power cord.

Break-in Period: The speaker will sound great out of the box & will get better over time. No need to do anything else, but listen to them. Do give them at least 30-50 hours of break-in time before doing any critical listening.