American manufacturer Koss has been making headphones since the 1960s. Established in 1953, today Koss produces a huge range of headphones, at all prices and quality levels.
Noise-cancelling technology is the latest trend in headphone design and the QZ77 Stereophones are from Koss’ Quiet Zone range, all of which employ noise-reduction techniques.
Packed in one of those fiendishly difficult to open retail blister packs, the QZ77 earphones are finished in matte-metallic silver, with chrome highlights and soft black foam earplugs. A replacement set of earplugs, a dual mono to stereo jack converter and a drawstring fabric storage sack are supplied in the pack.
Active Noise Reduction (ANR) works by using tiny microphones to sample the ambient noise reaching the ear. The microphone signal is analysed and an inverted version, of exactly the right phase and amplitude to cancel out the background noise, is added to the signal driving the headphones.
The technique works best on low frequency sounds because these are slower and less complex than the higher frequencies, therefore being easier to analyse and match. The high tech part of the noise cancellation, powered by a single AAA cell, lives in a silver plastic pod suspended from a nylon cord, neck lanyard.
The pod also has a belt/pocket clip, a power switch for the ANR circuit, a LED power indicator and a volume control. Noise reduction above 1,000Hz is provided by the passive effect (PNR) of the foam rubber earplugs.
The ANR is disappointing and most of the noise cancellation seems due to the passive effect of the foam earplugs. All the noise-cancelling technology aside, the QZ77’s don’t work well as headphones. They lack bass response and produce noticeable sound colouration, even compared to a pair of The Plug earbuds, which Koss states were used as the basis of the QZ77 design.
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