Design and features:The headphones work with or without the noise-canceling feature being turned on. You can use the noise-canceling feature without listening to music. These headphones can be used wirelessly with Bluetooth devices or can be cord connected. The cord has to be left connected in order to use the noise canceling feature when they are not in Bluetooth mode even if they are just being used for noise canceling rather than listening to an audio program. When cord connected they have medium-high sensitivity regardless of whether the noise canceling feature is turned on or off, so they can provide satisfying volume levels when used with home audio equipment and even lower-powered portable audio devices. The HD 4.50 BTNC has an integrated microphone and volume, music player function, and call connect/disconnect controls that work with paired Bluetooth devices. Additional features include NFC Bluetooth pairing and earcups that fold for ease of storage. This model comes with a detachable 56-inch long standard audio cable for cord connected use, a USB charging cable, and a carrying pouch. The free Sennheiser Cap Tune music player/equalizer app is available for download to Apple or Android smartphones; it acts as a audio playback app, provides various types of tonal adjustments, and includes Airplay (for Apple devices) and DLNA (for Android devices) audio WiFi network streaming.
Sound quality: We found the HD 4.50 BTNC provides excellent active noise reduction and sound quality that falls in the very good range - it reproduces music and voice very well although it does have some noticeable sonic quirks. The sound quality was the same in the noise cancelling mode regardless of whether it was used in the Bluetooth or cord connected mode, and the overall sound can be summarized as somewhat hazy, and a bit congested and constricted. Bass (as in bass drums, bass guitars, stand-up bass, etc.) has good impact and goes deep, but is a bit boomy and prominent. The midrange (voices, guitars, horns, etc.) is a bit thin, constricted (as in straightjacketed), and congested (think sonic traffic jam), somewhat hazy, and has a slight plastic resonance (something like what you would hear if you talked into a semi-rigid plastic cup). The treble (cymbals, the upper range of violins, etc.) is a bit subdued and smeared (sounds that should have a delicate shimmer sound blurred), and the upper treble is muted. The sound has a good sense of liveliness and is somewhat open -- sound-wise it almost seems like you don't have anything covering your ears. When the noise cancelling feature is turned off the sound changes from when the noise cancelling feature is on; and while these headphones sound the same in both Bluetooth and cord connected mode, the sound will differ depending on how well the ear seal around the ears. If the ear cup seal is optimal, compared to the noise cancelling on mode the bass and midrange both become fuller, the midrange looses its constriction and the plastic resonance is reduced but it gets more congested. The overall sound can be summarized as a bit bassy and somewhat congested and hazy; we found it to be still in the very good range and to be a slight improvement compared to when the noise cancelling feature is on. If the ear cup seal is not optimal compared to the noise cancelling mode the bass looses some impact and depth, and the midrange looses its constriction and becomes fuller, but it gets a bit more congested and the slight plastic resonance becomes more apparent. Although the sound is noticeably different it still falls in the same score range as when the noise cancelling feature is on. These headphones provide excellent noise reduction overall, but are directional and the noise cancelling characteristic changes depending on where the noise is coming from. When the noise is coming from the front more low frequency noise is cancelled so ambient noise may take on a hissy quality, as noise moves from the front to the back the noise cancellation becomes more even across the entire frequency range.
Comfort: We found that these headphones produce a sense of moderate pressure around the ears. Users with larger ears may find the over-the-ear fit of the ear pads feel cramped, or that the ear pads sit on, rather than around their ears. Users with smaller heads or narrower faces may find they can't get a good earpad seal around the ears which may affect the sound quality, especially when the noise cancellation feature is turned off (see the sound quality section for details). As typical of over-ear models the ear pads might feel hot and/or sticky after prolonged use.
