Frequency Response

• Each Sennheiser CX300 and Sennheiser CX500 headphone has a frequency response, which stands for the level of accuracy of sound that it generates. Therefore, the wider the range, the more accurate the sound. The Sennheiser CX300 has a frequency response range of 19 to 21,000 hertz. With a wider range of 17 to 22,000 Hz, the Sennheiser CX500 produces more accurate stereo audio.
  
  

Impedance and Sensitivity

• The Sennheiser CX300 and the Sennheiser CX500 have a certain level of electrical impedance. This is the measurement, in ohms, of the headphones' resistance to alternating current. Both headphones have a 16-ohm impedance. However, the sensitivity -- or sound pressure level -- of the CX500 is 113 decibels, compared to the CX300's 112 dB, thus indicating that the sound of the former is slightly more corrupted by noise than the latter.
  
  

Physical Description

• Each Sennheiser CX300 and Sennheiser CX500 has a cord that measures about 3 feet in length and has, at one end, a 2.5-millimeter plug for the headphone sockets of electronic devices such as MP3 players and personal computers. The CX300 is available in black, silver, white and pink. The CX500, on the other hand, offers three colors: gray, black and white.
  
  

Availability

• At the time of publication, Sennheiser no longer makes the CX500. However, the headphones are available at online retail outlets such as Amazon.com, selling within a price range of around $30 to $50. On the other hand, the Sennheiser CX300, is still in production. Customers can purchase it directly from the manufacturer for $80 at time of publication.