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Sennheiser CX 300-II Precision - Black

In-Ear Precision Enhanced Bass Headphones Stereo Earphones


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This item has been discontinued

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Powerful, Compact Sennheiser Sound

The Sennheiser CX 300 II in-ear headphones offer tremendous sound quality from an incredibly compact design. These precision stereo headphones feature enhanced bass response for a powerful, dynamic sound. Sennheiser designed these headphones with more than just sound quality in mind as these headphones look great and provide an even more comfortable, secure fit during use. The compact design of the CX 300 II's makes them an ideal partner for any portable music player. The headphones also include 3 different sizes of soft silicone ear tips, ensuring a comfortable fit for nearly any user.

Impressive Sound

Don't let their compact design fool you, the stylish Sennheiser CX 300 II headphones pack some serious punch. Their high output drivers provide that classic Sennheiser sound quality found in their on-ear and over-ear counterparts. These precision headphones provide enormous bass response for their size and the custom-fit ear canal is meant to deliver your music directly to your ear drums.

Rugged Design

The Sennheiser CX 300 II in-ear headphones aren't just engineered for outstanding sound. When designing these headphones, Sennheiser included a special Para-aramid reinforced cable to provide superior strength and reliability over traditional (weaker) headphone cables. The cable is also designed to be tangle-free for an easier, more convenient listening experience. The assymetrical design also allows for improved freedom of movement.

General Features:

  • In-Ear Precision Enhanced Bass Headphones/Earbuds
  • High output drivers for impressive low end response
  • Para-aramid reinforced cable for superior strength and reliability
  • Ideal for use with all MP3, iPad, iPod, iPhone
  • Tangle-free cable for convenient listening
  • Designed with a snug fit for active people
  • Gold-plated, corrosion-resistant stereo jack
  • Various ear adapter sets for maximum comfort
  • Original Sennheiser Earbud Extension Cable Available (525105)
  • Main Color: Black
  • Manufacturer Model Number: CX 300-II (CX300-II)
  • Manufacturer Part Number: 502737
  • Also Found As: Sennheiser CX 300II, CX300II, CX300-MKII, CX300MKII, CX 300-ll, CX 300-11, Version 2, Sennheiser CX 300B MK II (Black), CX 300B MKII
  • Authorized Internet Dealer
  • 2 Year Manufacturer's Warranty

Product Specifications:

  • Speaker Type: Dynamic Driver
  • Frequency Response: 19 Hz - 21,000 Hz
  • Sensitivity: 113 dB
  • Nominal Impedance: 16 Ohms
  • Pick-up pattern: Omni-directional
  • Cable Length: 3.96 Feet (1.2 Meters)

What's in the Box?

Sennheiser CX 300-II What's in the Box?
  1. Sennheiser CX 300-II Precision In-Ear Headphones
  2. Ear Adapter Set (S/M/L)
  3. Carrying Pouch

Headphone Design

Headphone Type

Headphone type refers to the construction of the headphones.

Around the Ear means that the headphones wrap around the ear to provide a secure fit. This is most often seen in active and sports headphones.

Around the Neck means that the headphones wrap around the neck. This is also seen in active and sports headphones.

Earbuds means that the right and left sides of the headphones are separated and will fit securely into the ear. These are small, compact, and user friendly.

Over the Head headphones mean that the right and left speakers are connected with a support that goes over the head and rests on top. This is the typical headphone type.

Earpiece Design

This is the design of the earpieces on the headphones. Some headphones go inside the ear, while others rest on the outside of the ear. This helps you know exactly what type of headphones you will be receiving.

In-Ear: The ear buds go into the ear. Most often, the right and left ear buds are two separate pieces.

Enclosed-Ear: Usually are found on the larger headphones. They rest on top of the ear and have padding for comfort, as well as enclosing the ear to the speaker. This type of headphone helps to filter out surrounding noise.

On-Ear: This type of headphone involves the speaker sitting gently on the ear without going in the ear or sealing it off.

Specifically For
Some headphones can use an IR Transmitter in your vehicle, while some can be plugged into your media device and be used on the go or at home.

This is the lifestyle that the headphones are designed for. Each style has unique features that make it perfect for particular people.

Designed for those that are active. These headphones are made to stay in the ear during workouts. Whether you frequent the gym a lot or go running outside in the fresh air, these active style headphones will be your best friend.

For those that need the best in music quality. These audiophile headphones are engineered to produce high fidelity and accurate audio replication.

Disc Jockeys (DJs) require a special type of headphone that can meet their professional needs. These headphones are durable, loud, and will often allow for one ear listening.

Fashion Enthusiast:
For those that want to make a fashion statement with their headphones. Not only are these headphones designed with great sound quality in mind, but also great looks!

This lifestyle speaks for itself! If you love video games and want a pair of headphones that will deliver explosive sound and allow you to communicate with others, this is where you need to shop!

Music Lover:
These headphones are made to sound great. They are designed to produce rich, brilliant sounds that will play your music in a manner that the artists would appreciate. These headphones are for those that love music.

Musical Production / Recording Artists:
You're a music creator. Whether you're producing and mixing it down or in the studio recording yourself, you need a pair of headphones that will reproduce the music perfectly without any coloration. Look here for reference quality studio monitoring headphones.

Headphones need to be affordable and durable to keep up with the student lifestyle. A variety of styles can be considered a pair of student headphones.

Those that often find themselves on planes or on the road a lot. These headphones are compact, lightweight, and have a portable design. Some of the headphones in this lifestyle will feature noise cancellation technology that will help shut out outside noise.


General Features

Noise Reduction technology removes unwanted noise from a signal. Background or ambient noise can be removed to produce clearer speech and enhanced hearing. Typically these Active Noise Canceling (ANC) headphones are powered and use batteries to activate the noise canceling technology. Also referred to as Noise Reduction or Noise Cancellation.
Headphone Connection
This is how the headphones connect to the audio source.

Corded means that the headphones use a cord to transfer the audio signal.

Wireless means that the audio signal is transmitted wirelessly to the headphones.

1/4" Stereo Jack Adapter
Some headphones will come with a 1/4" stereo jack adapter to connect the usual 3.5mm jack to a 1/4" stereo plug.

1/4" Stereo jack is a larger audio jack that select electronics have.

Volume Adjustment
Volume Adjustment means that the headphone (independent of the source) can adjust the playback volume. Many headphones and ear buds have in-line volume control, which allows adjusting the audible volume from a switch on the headphones cord. Other headphones have a volume knob on the headphone can.
Built-In Microphone
This means that the headphones or earbuds have a built-in microphone. This can be a microphone on the cord, built into the headphone, or even a boom microphone. These mics can be used for music devices like iPods, for Smartphones to make and receive calls, or for gaming purposes.
Frequency Response
The range of frequencies the speaker will reproduce (lowest frequency to the highest). Bigger is better, meaning the wider the range, the better. The optimal range is 20 - 20,000 Hz (which is the range of human hearing).
19 - 21000 Hz
An efficiency or sensitivity rating tells you how effectively a speaker converts power into sound. The higher the number, the more efficient the speaker and the louder it will play with the same input power. An efficient speaker helps you maximize your available power. Most sensitivity ratings measure the speaker's output with 1 watt of input, 1 meter from the speaker. Some speakers' sensitivity is measured with 2.83 volts of input, instead of 1 watt.
Efficiency (1w/1m) is not an accurate indicator of a subwoofer's output capability and should not be used as a comparison to other speakers or subwoofers to determine which one is "louder".
113 dB
Driver Type
The physical design of the driver in the headphones.
The opposition to electric current, a higher impedance means a higher electrical resistance. This is measured in ohms.
16 ohms

Warranty and Return Policy

Parts Warranty Duration
2 years
Labor Warranty Duration
2 years
Warranty Provider

Summary of Customer Ratings & Reviews

Rating Distribution

5 Star
4 Star
3 Star
2 Star
1 Star

Average Attribution Rating


Queens, NY

Awesome earbuds

September 7, 2014

I used to have these, but ended up losing them. I had Sennheiser IE8's and a couple of other skull candy's, so didn't want to spend more on getting them again. It's been around 2 years and always thought about them. I finally have them again and I am as much in love with them as before. These buds have great bass/sound and the fitting of them are very convenient. They sit flush or concave in regards to your ear lobe so that you can lie down and use them. For the price to the benefits, these are spectacular buds. Sure the IE8's sound slightly better, but they're heavier, should be wrapped around the ear, cost way much more. My favorite buds.

4 of 6 found this helpful

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August 14, 2014

Good product is one of my fovorites, i have to buy more of those.

3 of 4 found this helpful

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Granbury, Tx.

Good value

February 3, 2014

I bought these for about $40. At that price, they are an excellent deal. Good sound, comfortable fit. I use them with my ipod nano. I'd definitely recommend them.

2 of 4 found this helpful

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Browse 1 question and 2 answers
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Why did you choose this?
Sonic Electronix Store
listening while working out
Bing X on Aug 26, 2014
great discount
weishi y on Aug 7, 2014

Product Summary


Model Number

CX 300-II (Black)





Internal SKU


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Sonic Electronix Wiring Guide

Wiring Diagram Legend

Warning: The image depicted shows the resistance change when wiring multiple subwoofer terminals. Please refer to your subwoofer's owner's manual for the proper wiring of its terminals. Sonic Electronix, Inc. is not responsible for damage caused to your audio system or vehicle due to improper installation. Please call tech support at 1-877-289-7664 if you require additional assistance.

Product Name: Sennheiser CX 300-II Precision - Black