Sennheiser CX 300-II – Review

Sennheiser CX 300-II

Sennheiser CX 300-II

| Dynamic Driver |

? The Sennheiser CX 300-II are a very popular budget model from Sennheiser that has an incredibly small size and that Sennheiser markets as an earbud with “powerful” “big bass response”; we will determine this after running our Sennheiser CX 300-II soundtests.

Sennheiser is an ultra famous headphone and earphones company that you most probably already know and might have heard from.

The brand has a very large amount of highly famous models like the:

The housings of the Sennheiser CX 300-II are mainly built in plastic but also have a silver metallic ring. Their weight and size is minuscule, being the eartip as big as the housing itself. Sennheiser has not specified the size of the dynamic driver inside the housings but despite having tiny housings, a fairly large driver could be fitted inside, in the past we have reviewed other earphones that have similarly small sized housings like the JBL T110, Sony MDR-EX15LP, JBL C100SI, FISCHER AUDIO Dream Catcher and most had at least 8mm DD inside, besides the FISCHER AUDIO that holds the smallest DD in the world (3.8mm)

The Sennheiser CX 300-II features asymmetrical cables (a cable style that you might have seen in our review of the Sony MH1 Livesound) to reduce cable cluttering and have a rubberized finish to reduce tangling issues.

The Sennheiser CX 300-II is compatible with Android and Apple devices that have a 3.5mm headphone jack. Any smartphone with an USB Type-C or lightning connector will also be compatible with the Sennheiser CX 300-II by simply getting an USB Type-C to 3.5mm adapter or a lightning to 3.5mm adapter.

You can buy the Sennheiser CX 300-II in:

  • Sennheiser CX 300-II black
  • Sennheiser CX 300-II silver
  • Sennheiser CX 300-II white

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Sennheiser CX 300-II - Review

Tests & Scores



Sennheiser CX 300-II weight in Ounces and Sennheiser CX 300-II weight in grams.

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Accessories & Packaging

The Sennheiser CX 300-II unboxing results in 3 pair of eartips and a nice carrying pouch with the Sennheiser logo. The packaging, unfortunately, is a blister-styled one that you will have to combat with to open it up, not something too unusual but certainly not the most easy one to open.


Sennheiser CX300-II - Accessories
Sennheiser CX300-II – Accessories


Bass & Sub Bass

The Sennheiser CX 300-II bass is punchy and deep with a fun style that provides energy, strong mid-bass and good sub-bass to any type of genre. Mid-bass could feel a bit too strong if you were expecting a more classic/balanced sound style from Sennheiser but if you enjoy vigorous bass these in-ear headphones will most probably make you happy.

An EQ adds an evident amount of both punch and depth but bass will start to loose control.

When running the Sennheiser CX 300-II through our extreme basshead tests, they handled up to 47% of the maximum power coming from a Fiio E12 Mont Blanc amplifier while turning it’s bass boost on, high gain and applying a custom basshead EQ. The results were an outstanding increment of their mid-bass punch and sub-bass depth and reaching a very worthy basshead rumble and impact above the KZ ATE, Xiaomi Mi Pro HD, Panasonic RP-TCM 125 but still below the Sony MDR-XB50, Sony MDR-EX650, Pioneer SE-CX8, KZ ZST, Xiaomi Mi In-Ear Headphones Pro or the Sony MDR-7550 / Sony MDR-EX800st.


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Mids & Vocals

Mids of the Sennheiser CX300-II sound clear enough and energetic but exhibit some mid-bass bleed, higher mids are crisp and not rolled off nor harsh. Overall their mids sound warm, pleasant, with good higher mids and non-distant vocals but lower vocals might have to fight back a bit if the track being played has strong mid-bass.

Applying an EQ, lower vocals clear up and mid-bass bleed is reduced but if the overall EQ is overdone their vocals can risk to get a bit ecoish (if done correctly there will not be any issues). Higher mids can get a bit harshy if pushed too much.



Highs & Treble

The Sennheiser CX 300-II have bright highs and are able to resolve some mild detail. Piercing highs are not present but sibilance could be recurrently and strongly heard.

An EQ makes their highs very noticeably brighter, some extra detail is also resolved but not by a huge amount. Piercing highs still remain under control but sibiliance becomes stronger. A different approach can be taken regarding their high’s equalization, if you prefer you can aim your EQ to reduce sibilance instead of enhancing brightness and the Sennheiser CX 300-II will respond greatly with a very clear reduction of their sibilant vocals without taking out too much of their high’s brightness; if you want the ” EQ recipe”, just dial down frequencies near the 7 kHz and fine tune the nearby ones.


Sennheiser CX 300-II
Sennheiser CX 300-II


Sound Leak

The sound that leaks out of the Sennheiser CX 300-II is more or less inline with many average earphones, this means that their sound will be heard by nearby people if you crank the volume a bit past a moderate level but will not be too disturbing under normal city situations.


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Sound Isolation

Despite the very small size of the Sennheiser CX 300-II, they are able to offer a remarkable amount of sound isolation with a clearly subdued perception of your surroundings without having to apply a health-risking (for your ears) high volume.


Sennheiser CX 300-II
Sennheiser CX 300-II



The tiny footprint of the Sennheiser CX 300-II housings makes them fit inside any kind of ear’s size without becoming obtrusive nor uncomfortable but neither are too loose as to fall off the ears while being used on everyday activities. Moreover, by being so small and fitting deep they sit flat with the ears allowing them to be a very well featured in-ear headphone to be used under helmets or at bed. Due, to the aforementioned they are now part of our Best Earphones for Helmets Chart.


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Response to Equalization

The Sennheiser CX 300-II showed a clear response to our EQs, bass could be empowered with clearly extra punch and depth; mids benefited from mid-bass strength reduction and clearer lower vocals but just be cautious to not overdo the EQ. Highs could be either pushed for extra brightness and detail or for sibilance reduction with noticeable results.


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Frequency Response (raw)

Sennheiser CX 300-II Frequency Response

Sennheiser CX300 II frequency response curve
Sennheiser CX300 II frequency response curve

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Sennheiser CX 300-II


Driver Unitunknown
Power Capacity3mW
Impedance16 ohms
Frequency Response19-21,000Hz
CordAsymmetric, round cord
Cord Length1.2m
PlugStereo mini plug
Supplied Accessories3x Earphone tips; soft carrying pouch

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We highly discourage anyone from trying to apply our testings to your own earphones, the risk of damaging or permanently breaking your iems is absolutely probable to happen. With our standardized equalization and amplification tests we push the limits of the earphones to the extreme. If anyway you decide to do so, we cannot be held responsible of the damage done to your equipment. Do it at your own risk.

Sennheiser CX 300-II