The Sendy Audio Apollo PRO further develops the concept of the original Apollo: an open-back, over-ear planar magnetic headphone with natural wood ear cups and a premium mechanical construction. The open design is intended to support freer airflow and a wider sense of space, while the planar driver delivers fast, controlled diaphragm movement.

The most important upgrade in the Apollo PRO is its 78 mm driver, which is larger in diameter than the 68 mm planar unit used in the Apollo. The larger diaphragm surface allows more even sound energy distribution and more stable operation, while the total headphone weight has been reduced to 354 g, making it lighter than the previous Apollo model.

78 mm planar magnetic driver

A planar magnetic driver operates differently from traditional dynamic headphones. Conductive traces are placed across the surface of a thin diaphragm, which is moved more evenly by the magnetic field, allowing the diaphragm to function as a system driven across a larger surface rather than from a single point.

The Apollo PRO’s 78 mm driver uses a large diaphragm surface, which can contribute to controlled bass, fast transient response and more accurate detail reproduction. The 20 Hz - 40 kHz frequency response covers a wide operating range, while the 27 ohm impedance represents a relatively manageable load for a suitable headphone amplifier or high-quality portable player.

EB evaporation deposition technology

An aluminum circuit layer is applied to the Apollo PRO diaphragm surface using EB, or electron beam evaporation deposition. Its purpose is to create a dense, uniform coating that controls diaphragm vibration more precisely and improves the homogeneity of the surface conductive traces.

The atomic column structure of the coating supports diaphragm segmentation and vibration control. In practice, this is not merely a technical detail: more precise diaphragm control plays a role in helping the headphones handle fast attack sounds, low-level details and complex instrumental layers with greater stability.

Sound and character

Based on its technical design, the large-diameter planar diaphragm, low-mass composite structure and uniform aluminum conductive layer are intended to deliver fast, controlled sound and clean detail retrieval.

The open-back design is important for spatial presentation and a more airy performance. The bass range is expected to focus more on control and tightness than on the strong acoustic pressure typical of closed-back headphones. Midrange and treble reproduction are supported by the fast planar diaphragm, stable frequency response and detail-oriented driver architecture. Cable shielding helps reduce noise and support signal stability, but due to the open-back headphone design, external noise isolation should not be expected.

Tri-composite detachable cable

The factory cable supplied with the Apollo PRO combines three conductor materials: 30 strands of 0.05 mm Furukawa OFC copper, 10 strands of 0.05 mm silver-plated copper and 10 strands of 0.05 mm enamelled gold-plated copper form the conductor structure. This design targets stable signal transmission, fine detail retrieval and long-term reliability.

The cable comes with a 4.4 mm balanced connector, making it well suited for modern DAPs, DAC/headphone amplifiers and desktop headphone systems. The included 3.5 mm SE to 4.4 mm balanced adapter and 6.35 mm to 3.5 mm adapter help provide wider compatibility, especially with traditional headphone outputs and desktop amplifiers.

Shielded cable structure

The cable’s inner layer uses a graphene-reinforced PVC structure that provides both insulation and shielding against electromagnetic interference. This matters for wired headphones because longer cables and nearby electrical devices can create a more sensitive signal transmission environment.

The dual-shielding structure also improves mechanical durability. Higher tensile strength and a more stable signal path are especially useful with portable players, desktop DAC/AMP chains and cables that are frequently moved.

CNC-machined aluminum structure

The Apollo PRO uses CNC-machined aviation aluminum components designed to support mechanical stability and precise fit. Accurate machining is important at the headband, yokes and ear cup joints, because these parts are under continuous load during use.

The flexible adjustment system allows the headband and ear cups to conform more naturally to the shape of the head. This is not only a matter of comfort, but also important for sound quality, because proper fit ensures a more stable position around the ear.

Comfort for longer listening sessions

The soft lambskin headband provides a smoother touch and a more durable premium feel, while also helping distribute pressure across the head. The 354 g weight is favorable among planar headphones, especially considering the use of natural wood and metal components.

The breathable velvet ear pads provide a more skin-friendly contact surface, while the wider, softer padding reduces localized pressure points. The velvet surface also helps moderate heat buildup, which can provide a noticeable comfort advantage during longer listening sessions.

System integration and amplification

With its 27 ohm impedance and 93 dB ± 3 dB sensitivity, the Apollo PRO is not an extremely difficult headphone to drive, but planar magnetic drivers typically benefit from a source with stable current delivery. A high-quality desktop or portable DAC/AMP can provide more precise control and greater dynamic headroom.

The 4.4 mm balanced connection is advantageous with modern headphone amplifiers, as compatible outputs often offer higher power and better channel separation. With the included adapters, the Apollo PRO can also be used with several classic headphone outputs.