Sennheiser CX 300-II PRECISION Noise Isolating In-Ear-Canalphone Review
By: Michael Phrakaysone


Most of us are familiar with earphones.  These ‘small speakers’ have been out for as long as I could remember bundled with portable devices such as those retro Gameboy’s and today’s MP3 players. 

Earphones come in several varieties, are easy to make and inexpensive to produce.  They are convenient compared to full-size headphones that you don’t want to bring along with you and both exhibit different characteristics.  Typical earphones are ones that you stuck on the out outside of your ear canal.  They are still present in today’s market but that is quickly changing. 

New earphone designs now allow the penetration of the actual driver inside your ears sealed but what looks like earplugs creating a barrier between what you hear and external ambient noise.  By cancelling outside noise, you don’t need to use as much volume as before to hear music and it provides an experience that feels like you are hearing the music live at a concert allowing you to feel connected to your music.  In fact these new noise isolating earphones provide superior noise reduction than anything out there right now, providing a minimum of 10dB reduction of ambient noise and that number goes upwards from there from product to product and material to material.    

Note: Many names can be given for these new earphones.  In-ear earphones/canal headphones, canalphones, in-ear monitors (IEM) all mean the same thing.  I’ll call them in-ear-canalphones.

Today I will be reviewing the Sennheiser CX 300-II PRECISION noise isolating in-ear-canalphone.

About Sennheiser

Sennheiser was founded in 1945 and is a very well known German company that is highly respected among the audio world that has been making microphones, headsets, telephony accessories and aviation products for a long time.  If there’s ever a company to trust when looking for audio gear, Sennheiser would be one of them.

Sennheiser CX 300-II PRECISION General Description and Features

General Description

Offering a powerful, bass-driven stereo sound with greater clarity and improved dynamics are the CX 300-II Precision Black ear-canal phones. The various sizes of ear adapters (S/M/L sizes) provided in the package allow for a personalised fit as well as a high passive attenuation of ambient noise. Also, the asymmetrical cable design ensures a high wearing comfort as you listen on the go.


  • High-quality dynamic speaker systems for powerful, bass-driven stereo sound
  • Excellent fit in the ear canals and high attenuation of ambient noise (ear adapters in different sizes included)
  • Convenient carrying pouch included
  • Optimised for MP3, iPod, iPhone, CD players and portable gaming systems (iPod and iPhone are trademarks of Apple Inc. registered in the U.S. and other countries)
  • Asymmetrical cable
  • 2-year warranty


Delivery Includes

  • Carrying pouch
  • Ear adapter set (S/M/L)
  • CX 300-II ear-canal phones

Sennheiser CX 300-II PRECISION Product Specification

Technical Data

Cable length

3.9 ft. (1.2 m)

Frequency response (headphones)

19 Hz-21,000 Hz


16 Ω

Jack plug

3.5 mm. (angled)

Sound pressure level (SPL)

113 dB (1kHz/1Vrms)

Transducer principle


The Sennheiser CX 300-II PRECISION comes in an elegant looking plastic blister packaging.  These ones are hard to open so you’re going to have to use scissors or a blade to open these up.  The canalphones are shown right in the middle of the packaging and the inserts right beside.  You’ll notice right off the bat the red words “precise bass” and “iPod”.  The CX 300-II is an upgrade to the original CX-300 canalphone and is claimed to have better bass, clarity and overall dynamics.

The Sennheiser CX 300-II sells for a midrange price of $99.99CAD but looking around further can be found for $89.99 making it an attractive purchase.  With your purchase of the CX 300-II, contents will include…

  • Sennheiser CX 300-II In-Ear-Canalphones
  • Ear Insert Set (Small, Medium and Large)
  • Soft carrying pouch

The Sennheiser CX 300-II comes in five different colors.  The colors are black, silver, white, red and pink.  The one I am reviewing is in the traditional black color.  At first glance, I’m going to be honest as the CX 300-II look very low key and definitely not a stand out.  And that can be a good thing as it will not attract attention.  As the saying goes “don't judge a book by its cover”.  The most important thing is sound quality and comfort.

Included with the CX 300-II is one pair of each size soft ear inserts.  I believe the ear inserts are rubber.  The inserts feel soft, stretchy and the result is a very comfortable fit in my ear.  I have to say that the CX 300-II is without a doubt the most comfortable canalphone I have experienced.  I believe the combination of the canalphone design with the addition of these soft rubber ear-inserts have made a perfect combination.

Unlike the easy installation of just pushing on the insert on the canalphone as was such with the MetroFi 220vi, the CX 300-II requires a little more effort.  You can’t just push them on the canalphone opening but rather takes a little stretching over the canalphone to become seated in the ridge.
The CX 300-II has no color-coding scheme that reveals which is for the right or left ear, but rather has text specifying “L” and “R”.  The only other way you can tell which canalphone is for which ear is by locating the longer cord.  The “R” canalphone has a longer cord whereas the shorter cord is for the left ear.

The CX 300-II has a dynamic driver that is covered by a grille that prevents earwax from entering which is a nice little touch.  Earwax unfortunately can stay on the grille blocking the sound so you have to remove it if such a thing happens.  Including a small brush would have been welcome.

When using canalphones a characteristic you will come to experience is one that feels like you’re somehow underneath water where you can hear you’re every movement.  That’s the same feeling you will have when wearing canalphones but the movements you hear will be from the cord shuffling about against your body and also your own voice/breath.  There’s nothing you can do about the latter but with the former, a clip that could hold the cord against your shirt would probably help.

I have small ear openings so I utilized the small silicone inserts since the bigger ones would not fit.  As I stated previously, the rubber inserts are so soft that they provide a really comfortable fitment with no weird sensation.  These are without a doubt, the best fitment I have experience with canalphones to date.  The CX 300-II is very comfortable and during usage, they don’t fall out.

The rubber inserts provide very good noise isolation.  I feel they are comparable to the silicone inserts offered by Ultimate Ears.  In real world testing they drown out most of the external noise and allow you to listen to your music without the commotion of the outside world.

Sound Quality

The Sennheiser CX 300-II is a top performer.  In my review of the Ultimate Ears MetroFi 220vi’s, I was impressed by the bass but disappointed by the 5% missing vibrancy and desired a little more treble to bring out the clarity.  Well with the Sennheiser CX 300-II, there is very little weakness and only impressive sound.  This could very well be the best sounding canalphone I have heard to date. 

First of all I tested the Sennheiser CX 300-II on my computer with an M-Audio Audiophile 2496 soundcard instead of testing it on any sort of MP3 player.  I chose this for sound quality reasons; this setup provides unparalleled sound quality over any source available to me.  Next I listened to audio CD’s and 320kbs encoded MP3’s, OGGs and FLAC music with a flat equalizer.

I also “broke-in” the canalphones through about 48 hours of “pink-noise” looping over and over.  This is to supposedly open up the dynamic drivers the Sennheiser CX 300-II contains.

When I test anything sound related, the most important thing I’m looking for is balance between low, mid and high frequencies.  I should not be able to distinguish a prominent characteristic if the product is balanced.

Low frequency – The Sennheiser CX 300-II provides very good bass.  Whereas the UE MetroFi 220vi provided excellent bass but took away from the clarity, the Sennheiser CX 300-II offers very good level of bass but does not take away clarity from the other frequencies.  The quality amongst low, medium and highs remain intact.  Listening to a heartbeat, you’re still going to get smooth pounding bass, just at one level below the MetroFi 220vi.

Mid frequency – The Sennheiser CX 300-II provides excellent mid-frequency production.  Voices are clear and instruments have a melodious feeling.

High frequency – Whereas the MetroFi 220vi falters, the Sennheiser CX 300-II does not.  The clarity is clearly evident between the two canalphones.  The CX 300-II provides a very good performance here with little distortion and just clean sound.  The amount of treble offered is perfect and the vibrancy of the CX 300-II as a whole is totally satisfying.


I don’t think for the price you can get any better and for that reason it gets the Editors Choice Award.  The Sennheiser CX 300-II just sounds balanced throughout the ranges and offers a high level of detail.  It offers excellent sound, excellent comfort and it is affordable. 

This is indeed my “go-to” canalphone.  I guess the only cons aren’t really cons toward the canalphone but with the lack of accessory, sleeper look and there should be a clip to prevent the wires from floating around.

Pros and Cons

    • + Balanced sound
    • + Soft pouch
    • + Maximum comfort
    • + Effective noise isolation
    • - Can hear cord dangle around
    • - Should include a brush for maintenance purposes
    • - They can look boring to some


    Editors Choice


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