Koss QZ-50 Wireless Headphones

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The Koss QZ50 Noise Reduction Stereophones - Do These Even Deserve the Koss Name?

Mar 14, 2006
Review by  
Rated a Very Helpful Review

Pros:Low price, lifetime warranty

Cons:Poor noise cancelling peformance, poor sound reproduction in general, no extras included

The Bottom Line: Poor noise canceling performance and an overall poor listening experience. Leave these on the shelf.


Koss QZ 50 Noise Reduction Stereophones are the cheapest Active Noise Reduction (ANR) Technology noise cancelling headphones in the Koss lineup of active and passive noise cancelling headphones. I’ve found the QZ50’s performance to be mediocre, surprisingly, since most inexpensive Koss headphones that I’ve tried have been terrific, the $30 KSC-35’s, and the even cheaper KSC-55’s and KTZPro1’s that I keep attached to PC’s in my home.

I had purchased the inexpensive Aiwa HP-CN6 noise cancelling headphones (only $18 from Amazon, at the time) a few months ago, and was really pleased with how well they worked. My wife is planning a couple of plane trips this year, and recently showed interest in owning a pair of noise cancelling headphones. When these went on sale at Compusa for $20, I picked up a pair, though I now wish I had purchased another set of the Aiwa HP-CN6’s instead.

The QZ-50 specifications, at least those that Koss provides, are promising:
- Reduces low frequency ambient noise levels by 15db
- Freq. response 30-20,000 hz
- Impedance: 32 ohms
- Sensitivity: 98dB SPL/1mw
- Less than 0.3% distortion

The relatively low impedance and fairly high sensitivity indicate that these headphones should work well with portable cd and mp3 players with low power outputs. (They’re probably not be the best fit for high power amplifiers, where they could be easily overloaded.) The frequency response range is not quite as good as most standard (non-noise canceling) headphones, but the advertised numbers are better than the quoted specs for the Aiwa HP-CN6 ‘phones that I also own. The 15db reduction in low frequency noise is also an impressive stat, though I doubt they provide anywhere near that reduction in the applications that I’ve tried.

No extra’s come with these headphones. No 1/8 X 1/4" adapter, no carrying case etc. Most other models in this price range come with a two prong adapter to fit airplane headphone jacks, and a carrying case.

How They Work

Koss sells both active and passive noise cancelling headphones. Passive models block noise by sealing off your ears from outside sounds. Active models actually “cancel” sound, though only in the lower end of the mid-frequency range. Koss describes their noise cancelling technology as follows:

Active noise reduction technology in stereophones creates an invisible shield between the listener and the droning sounds of the world by stopping low frequency noise before it reaches the ears. Tiny microphones are embedded in the stereophone ear cups. These microphones read the surrounding low frequency noise and transmit information about those undesirable sounds to a processor in a pocket sized control case. The processor, in turn, generates mirror image anti-waves that are 180 degrees out of phase and relays those anti-waves back to the stereophones. When the offending sound waves encounter the waves generated by noise reduction technology, the two counteract each other at the wearer's ear. The offending hum and buzz is reduced and a peaceful listening environment is created where once there was only noise. Lawn mowers, jet engines, crowded environments, vacuum cleaners, computer fans or any other low frequency noise below 1000 Hz can be reduced by an average of 10dB by Koss' Noise Reduction Stereophone the Quiet Zone 2000. Quiet Zone noise reduction is even greater for noise below 200 Hz, offering at least 15dB of protection against low frequency noise.

The individual earphones on the QZ-50’s are about the same diameter as your ears, though they are among the thickest you’ll see, at just under 2”. The earpieces are connected by a “behind the neck” headband, which I find more comfortable and stable than headbands that fit across the top of your head. On the outside of each earpiece is a small microphone which picks up ambient noise and uses that data to cancel out ambient noise. On the left headphone is an on-off switch. In the off position, the headphones work like any other model, with no noise reduction. Turning the switch on activates a red LED and the noise dampening circuitry.

How Well do these Noise Cancelling Headphones Work?

I purchased my first set of noise cancelling headphones (Aiwa HP-CN6’s) to listen to my mp3 player while mowing the yard. For this application, those headphones worked quite well. Turning on the headphones while mowing immediately cuts the mower’s sound down by a lot, more than half. They worked so well that my wife suggested she would like a pair also. The next time I saw a pair of noise cancelling headphones on sale was when this Koss model was marked down to $20. Unfortunately, I regret the purchase. In the applications where I found the Aiwa ‘phones so effective, either running the lawn mower or edger, or working around computers with annoyingly loud fans, these Koss noise cancelling headphones were much less effective. I can detect a small amount of noise reduction, but the amount of reduction is minimal, not enough to justify wearing these headphones.

To get a better quantify for how well these headphones worker, I downloaded the NCH tone generator for my PC (http://www.nch.com.au/tonegen/index.html) and played back tones from 100hz to 1500 hz on my PC. I then subjectively listened to both the Koss QZ50 and Aiwa HP-CN6 headphones, trying to determine how well each blocked the sound generated by the tone generator.

- Tones at 1000-1500 hz were not effectively cancelled by either model. I could detect a slight reduction by the Aiwa ‘phones, but not by the Koss model reviewed here.

- Between 600-1000 hz, I could detect no cancelling when using the Koss QZ-50’s. The Aiwa HP-CN6 ‘phones canceled some part of the sound, the reduction was noticeable, perhaps 25% or so, but still not really helpful

- At 300-500 hz, I felt the Aiwa headphones were blocking enough sound, perhaps 40-50% to be worth wearing. The cancelling from the Koss phones was still minimal.

- Both headphones reduced the 100-200 hz tones enough to be worth wearing. The Aiwa model was still more effective, even at this frequency.

Sound quality I can’t even report that the Koss headphones provided a better listening experience. The bass response is ok, but the mid and high range frequencies are muddy and indistinct. I even found listening to spoken words a little difficult. Even though the Koss headphones advertise a wider frequency response than the Aiwa headphones, I found I much preferred listening to music and voice with the Aiwa noise canceling headphones.

Comfort and Ease of Use The weight of the headphones is only 4.5 ounces, with battery installed, light enough to remain comfortable after an hour or two of listening. These headphones are still a little uncomfortable to wear, when compared to most non – noise canceling models, but the comfort level is acceptable.

Battery life is excellent. I’m still on my first battery after a couple of weeks of use. Koss suggests the single AAA battery included with these headphones will last 200 hours. The poor noise canceling performance of these headphones is at least consistent with the long battery life, the noise canceling circuitry isn’t doing much that would require power from the battery I’m guessing.

These headphones are suitable for use with low power portable audio players. The seem to play just as loud with my mp3 player as any of the other headphone’s I’ve used. Another one of the few pluses for this model.

I’m really disappointed with these headphones. With the Koss name, I expected top notch performance, but its just not there. The noise canceling performance is poor, and the sound reproduction quality is poor. Its nice that these headphones are reasonably comfortable, offer a great warranty, and terrific battery life, but who cares if the listening experience is unsatisfactory.


Recommend this product? No


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