Sennheiser CX300S Pure Bass Wired Earphone

Sennheiser Transducer

German-Engineered Driver — 17Hz to 21kHz

Sennheiser uses the term transducer to describe the complete driver assembly — voice coil, cone, magnet system and acoustic enclosure — which they engineer as an integrated unit rather than specifying individual components separately. The CX 300S uses a closed-back dynamic transducer principle: the rear of the driver is enclosed and acoustically isolated, which prevents rear-wave cancellation from reducing bass output and improves bass definition at the low end of the frequency range. The 17Hz–21kHz frequency response extends beyond the nominal 20Hz–20kHz range of human hearing at both extremes — the sub-bass extension below 20Hz contributes to the physical sensation of bass instruments at high playback levels, while the 21kHz high-frequency extension ensures the driver is operating comfortably within its range at the top of the audible spectrum rather than at its limit. The 18Ω impedance is matched to the output capability of consumer devices and requires no amplification beyond a standard headphone socket.

Four Eartip Sizes · XS/S/M/L

Individualised Fit — Acoustic Seal for Bass

Four eartip sizes — XS, S, M and L — are included rather than the three sizes (S/M/L) standard in most wired earphone packages. The additional XS size accommodates the smaller ear canal diameters that S tips may not seal correctly, ensuring the full range of users can achieve a proper acoustic seal. The seal is not simply a comfort question: when the eartip seals against the ear canal walls, the bass from the driver builds up in the sealed space between the tip and the eardrum rather than leaking away. A correct seal makes a measurable difference to bass response — the same earphone can sound thin and bass-light with an oversized tip and full and impactful with the correct size. The in-ear canal design also provides passive noise isolation by physically blocking the ear canal, attenuating ambient sound without any active electronics.

L-Shaped Jack · Flat Cable

Connector Design — Tangle Resistant

The L-shaped 3.5mm connector is a practical engineering choice: when the cable runs from a phone in a pocket, a straight connector creates a 90° bend at the entry point under tension, which is the location where cable failures most commonly occur. The L-shape allows the connector to exit the socket at an angle parallel to the device surface, removing the bending stress and significantly extending the cable’s service life at the connector junction. The 1.2m flat ribbon cable resists the axial twisting that causes round cables to knot, so the earphones emerge from a pocket or bag ready to use without untangling. A storage pouch is included for protecting the earphones when not in use and for keeping the cable organised during storage.

Great choice if you…

✔ Want German-engineered Sennheiser transducer quality in a wired earphone
✔ Need four eartip sizes for an individualised canal fit
✔ Want passive noise isolation without active electronics
✔ Need reliable wired earphones that never need charging
✔ Use any device with a 3.5mm headphone jack

Consider something else if…

✖ Your phone has no 3.5mm jack — you will need a USB-C or Lightning adapter
✖ You need volume up/down on the remote — the CX 300S has a single-button remote only
✖ You want wireless — see the Sennheiser CX or Momentum True Wireless range

Technical Specifications

Box Contents

Condition

Brand New — Retail Packaging

Warranty

1 Year Sennheiser

Delivery

4–5 Working Days · Fully Tracked