Alphateta HDJ-F9

The AlphaTheta HDJ-F9 is a professional, wireless, closed-back, on-ear DJ headset designed for monitoring and mixing in the DJ booth. Its ultra-low-latency SonicLink technology lets you mix and scratch without the constraints of a cable, while maintaining the responsiveness needed to control transitions.

Key Features

• SonicLink technology with latency as low as 9 ms for wireless control of your mixes and scratches.
• SonicLink Touch Pairing for quick connection to compatible equipment, including the DJM-V5 mixer.
• Closed-back, dual-chamber design offering passive isolation suitable for monitoring in noisy DJ booths.
• 40 mm drivers with PEEK-PU-PEEK diaphragms and a bass-reflex chamber, engineered to reproduce kick drum attacks and bass lines.
• Swivel ear cups and a flexible headband allow you to easily switch between listening with both ears and monitoring with just one ear.
• Bluetooth 5.3 multipoint for everyday listening and a removable coiled cable for a wired connection.

SonicLink and wireless DJ monitoring

SonicLink technology ensures audio transmission with latency as low as 9 ms. Unlike a standard Bluetooth connection, it’s designed to meet the needs of DJ monitoring, especially when you’re syncing two tracks, preparing a transition, or scratching.

The SonicLink Touch Pairing feature allows you to pair the HDJ-F9 simply by touching it to compatible equipment, such as the AlphaTheta DJM-V5 mixer, which must have up-to-date firmware. To use SonicLink with a mixer that doesn’t support this technology, the HP-TX01 transmitter is required. It is sold separately and is not included with the headphones.

Sound Quality and Noise Isolation

The HDJ-F9 uses 40 mm dynamic drivers equipped with a PEEK-PU-PEEK composite diaphragm. According to AlphaTheta, this design minimizes unwanted vibrations to reproduce midrange and high frequencies with low distortion. A bass-reflex chamber integrated into each ear cup helps reproduce defined bass and better distinguish kick drum attacks and basslines during mixing.

Its closed-back, on-ear design positions the ear cushions over the ears. The dual-chamber acoustic housing passively reduces external noise to facilitate monitoring in noisy environments. However, this isolation does not eliminate all ambient noise and does not rely on an active noise-canceling system.

Comfort and Handling on Stage

The swivel ear cups make it easy to change positions during a performance. You can listen with both ears, uncover one ear to monitor the booth feed, or let the headphones rest around your neck between sets.

The flexible silicone headband and die-cast aluminum adjustment system support these movements. Weighing 285 g without the cable, the HDJ-F9 remains relatively compact. Its polyurethane ear pads with a faux-leather finish rest directly on the ears, with comfort depending largely on your head shape and the duration of use.

Bluetooth and Customization

In addition to SonicLink, the HDJ-F9 features Bluetooth 5.3 with SBC and AAC codecs. Its multipoint connection allows you to connect two devices simultaneously, such as a smartphone and a computer. Google Fast Pair and Windows Swift Pair simplify pairing with compatible devices. The built-in microphone is designed for hands-free phone calls via Bluetooth, but the user manual does not cover its use with calling apps on computers or smartphones.

The HEADPHONES CONNECT app lets you adjust the color and brightness of the status LED, customize certain controls, and manage the auto-off feature. It also offers a find-my-headphones feature that makes the headphones emit a sound, as well as access to firmware updates. Using the app requires a Bluetooth connection, and the iOS version is scheduled for a later release.

Battery Life and Charging

With the status LED turned off, the HDJ-F9 offers up to 9 hours of battery life via SonicLink and 25 hours via Bluetooth, according to specifications provided by AlphaTheta. When the LED remains on, these times drop to approximately 7 hours and 13 hours, respectively. Actual battery life varies depending on volume and usage conditions, among other factors.

A full charge takes about 2 hours and 30 minutes. A 30-minute quick charge provides about 2 hours and 30 minutes of use in SonicLink mode. Charging is done via USB-C, but wireless connections cannot be used while charging.

Wired Connection and Accessories

The HDJ-F9 can also be plugged directly into a headphone output using the included detachable coiled cable. The cable is 1.2 m long and can stretch to approximately 3 m. Its bayonet-lock connector helps prevent accidental disconnections during use. Wired mode works without turning on the headphones and disables wireless connections.

The headphones come with a 6.35 mm screw-on stereo jack adapter for devices with this type of output, a 0.5 m USB-C to USB-C charging cable, and a carrying pouch. A compatible USB power adapter must be purchased separately if you do not already have one.