Sennheiser HD 660 S Specifications, Tests and Review

The Sennheiser HD 660 S are wired headphones. In the case of studio and professional DJ headphones, a wired connection is a standard and a necessity. In this case, connecting via cable reduces audio transmission delays and prevents unwanted battery drain as it would be in case of wireless headphones. The same is de facto true for gaming headsets. In case of headphones for normal music listening, the cable is rather a relic, although it still has its fans. However, the wireless option is much more popular for everyday use in today’s world.

The design of the headphones is around the ears. Because of this design, the headphone envelops the entire ear and isolates the ear better from surrounding noise when listening compared to for example on-ear headphones. With that, they offer high-quality listening without interference. However, they are most likely heavier by design and less practical for frequent carrying. The weight of the headphones is 260 g.

The sound quality can be affected by many factors. When it comes to frequency range, the wider it is, the more detail you will hear when listening. However, the range a person can perceive is highly individual. The average person is able to perceive frequencies in the range of 16 to 20 000 Hz. So the most common frequency range you will see on the market is 20 to 20,000 Hz. Lower frequencies up to approximately 256 Hz are considered bass frequencies. Therefore, the lower the bottom value is, the better the headphones will reproduce bass. Conversely, values from approximately 2 048 Hz upwards are treble. That is why headphones with a high upper value will provide a much more accurate reproduction of high notes. Sennheiser HD 660 S offers a frequency range of 9 - 41500 Hz. The sensitivity parameter determines how sensitively the headphones can receive the signal from the source. The higher the sensitivity value, the louder the headphones will be able to play with less power consumption. In general, a higher listening volume also means a higher power load for the connected device. So if you're buying headphones to listen to music from your mobile phone, for example, this is relevant to think about as you don't want to drain your phone's battery too much. Lower values around 85 dB are more suitable for listening in more quiet environments (for example, at home or in the office). Medium values of around 90 dB can provide good listening quality in noisier environments (for example, on public transport or in cafés). Headphones with high sensitivity values of around 100 dB or more are designed for really noisy environments, such as concerts. The Sennheiser HD 660 S has 104 dB/Vrms.

The device connected to the headphones also plays a role most times. The lower impedance value (approximately 100 to 150 Ohms) is suitable for playback from mobile phones, laptops or other portable players that do not have a powerful enough amplifier. The lower impedance will ensure that the required volume level is achieved with less power, thus extending the life of the player. However, at the same time, with lower impedance, there is more distortion of the sound. Headphones with a higher impedance of around 250 Ohms and above are then more suitable for playback from really powerful signal sources or using a headphone amplifier, otherwise the sound coming out of them might not be loud enough. At the same time, higher-impedance headphones will also ensure less distortion in the sound. In the case of these headphones, the impedance reaches the 150 Ohm value. Total harmonic distortion is one of the parameters you will come across and usually includes the average value of the distortion when reproducing all frequency bands. This parameter is not critical when choosing headphones, but it is important to remember that higher harmonic distortion can negatively affect sound quality. In case of these headphones, the total harmonic distortion is Audio Output | Total Harmonic Distortion.

The design of the headphones and their earcups can also affect the quality of the audio output. The open design ensures better sound reproduction with less distortion. On the other hand, it lets ambient noise in, but also lets sound from the headphones out. Therefore, choose the open design for home use or in quiet environments.