Koss JR 900 Specifications, Tests and Review

​​The Koss JR 900 are wireless headphones. The wireless connection allows absolute freedom of movement and with that increases the comfort of using the headphones. This feature is very popular, especially when using headphones every day. The limiting factor of wireless headphones is a certain delay in the sound transmission between the source and the headphones (almost indistinguishable for a normal user), as well as the need to charge them (in the case of wired headphones, the headphones are recharged by connecting the cable itself).

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 285 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. Koss JR 900 offers a frequency range of 20 - 20000 Hz.

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 10 kOhm 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.

In terms of headphone battery life as a significant factor in the purchase decision, it depends on what you want to use the headphones for and potentially how often you will be able to recharge them. Headphones with up to a few hours of battery life are more suitable for home use as they will require more frequent charging. Headphones with a battery life of around 10 hours or more are already more suitable for commuting and shorter journeys. However, nowadays you can also find headphones on the market that have a battery life in the higher tens to hundreds of hours. In this case, you do not have to worry about your headphones simply running out of power on longer journeys, and you will not have to deal with constant recharging. The battery life of the Koss JR 900 reaches up to 10 hour(s).