Sennheiser CX True Wireless (Black) review

This research-based review concerns Sennheiser's U.S. Black CX True Wireless, article 508973. The U.S. product page now labels the model end-of-life; its specifications and instructions are useful for understanding a specific older configuration, not evidence of a safe or available offer. No listening, fit, call, battery, or noise-cancellation testing was performed for this assessment.

A sealed tip, not active cancellation

CX True Wireless is a sealed in-ear design. Sennheiser's 2021 FAQ lists four silicone adapter sizes—XS, S, M and L—and says that turning the earbuds slightly helps seat them. That geometry can create passive isolation when a tip forms a good seal; it is not active noise cancellation, and fit depends on the wearer's ears. Choose a size that seals without pressure and assess each ear separately. The maker's instructions explain the process, but neither they nor the product image establish comfort or a personal seal.

The model has no active ANC. If cancellation is a requirement, the CX should not be treated as a match based on its passive isolation wording or adjustable equalizer. Conversely, listeners who prefer a sealed-tip construction and do not need ANC can compare its physical arrangement with current sealed models. The historical documentation does not establish how it performs against modern competitors.

Codec support and device switching are separate decisions

Sennheiser documents SBC, AAC and aptX over Bluetooth 5.2. Those names describe supported Bluetooth audio codecs, not a guaranteed choice on every phone or computer; the source host and its settings still matter. The available evidence supports Classic Audio codec options, but it does not provide a CX-specific runtime number for each codec, so none is assigned here.

The manual identifies up to eight remembered Bluetooth pairings, but the FAQ explicitly limits the earbuds to one connected device at a time. Switching sources means disconnecting the current device and selecting the earbuds on the next one. That is different from multipoint, where two devices can remain connected concurrently, and it is not the same as playing two streams at once. A two-device-simultaneous requirement therefore rules this model out.

Read the battery claim as a ceiling

The model FAQ states up to nine hours of playback from a charge and up to 27 hours in total when the case is used for recharging. Those are manufacturer maximum claims, not observed results; the document does not give a codec-specific nine-hour figure or an ANC-on figure. Because this model has no ANC, a requested minimum for ANC-on hours is not applicable even if the ordinary music maximum is numerically high. Do not turn the case-assisted total into one continuous listening session or apply it to an older battery of unknown condition.

The case charges by USB-C and does not support wireless charging. Sennheiser says the earbuds are IPX4 splash resistant, while the case is not splash resistant. The FAQ says not to submerge, shower with or rinse the earbuds, and to dry them before returning them to the case; it also cautions against charging wet buds. IPX4 describes a specific splash-resistance test, not waterproofing.

App options and aging-unit checks

Sennheiser says the earbuds can play music, handle calls and access a voice assistant without the Smart Control app. The app adds EQ and Bass Boost, touch-control customization, voice-prompt language settings and firmware updates. The FAQ also states that the batteries in both earbuds and case cannot be exchanged. Those facts make the model easier to characterize, but they do not tell us how much capacity remains in a used or long-stored example.

The matching Black image is a manufacturer appearance reference only. Sennheiser's U.S. selector identifies a separate White finish, article 508974; the official page and variant record support a finish-only relationship, not a different feature set. Confirm that any listing is a complete pair with its matching case rather than an individual OEM replacement earbud. This distinction matters because Sennheiser also lists the left and right replacement parts separately, and their detail-page compatibility wording names CX 400 BT rather than CX True Wireless.

Consider the CX True Wireless only as a documented earlier-model reference if sealed tips, no ANC, one-at-a-time device switching, USB-C wired case charging and earbuds-only IPX4 match your needs. The model is marked end-of-life on Sennheiser's U.S. page. Before considering any older offer, check exact article number and included case, seller condition, battery condition, returns and warranty. None of those offer-specific details was verified here.

Black and White are separate exact finishes

Sennheiser's U.S. selector identifies Black 508973 and White 508974 under the CX200TW1 family. The checked sources do not disclose a finish-dependent feature change. The images below are appearance references only; they do not establish any seller's package, battery condition or stock.

Sources: Sennheiser U.S. product page, CX True Wireless FAQ and CX200TW1 instruction manual.