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KOSS Black QZ-99 3.5mm/ 6.3mm Connector Circumaural Headphone

  • 40Hz-20KHz
  • 3.5mm/ 6.3mm Connector
  • Coiled, Single Entry, 8ft Cord Length

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  • Overview
  • Specifications
  • Warranty & Returns
  • Reviews


KOSS QZ99 Passive Noise Reduction Headphones

The Koss QZ99 Passive Noise Reduction headphones were initially designed for racing radio scanner and metal detector users, with its superior isolating capabilities and secure over-the-head headband design. It has since become a favorite for audiophiles who crave the ability to cut out high levels of ambient noise. The QZ99 are not only for noise isolation, but also for sound quality.

The QZ99 Passive Noise Reduction headphones sport neodymium magnet structures that deliver outstanding clarity and definition. The closed Pneumalite™ ear cushions and extra-secure headband create a tight seal around the ear eliminating all ambient noise. Durable and built to withstand the rigors of indoor and outdoor use, the Koss QZ99 also includes a volume control on the ear cup that makes adjusting sound levels a snap, and a stereo/mono switch that extends user flexibility. Sporty and strong with superior sound quality, these Passive Noise Reduction headphones are every audiophile’s dream.


  • Neodymium magnet structures deliver outstanding clarity and definition
  • Closed Pneumalite™ ear cushions and extra-secure headband seal ears, eliminate all ambient noise
  • Volume control on ear cup allows easy level adjustment
  • Stereo/mono switch extends user flexibility
  • Includes 8 foot, coiled, single-entry cord with 3.5mm plug and 6.3mm adapter
  • Covered under the Koss Stereophones Limited Lifetime Warranty


Frequency Response 40 - 20,000Hz
Impedance 60 Ohms
Sensitivity 102dB SPL/1mW
Cord Coiled, Single Entry, 8 feet with 3.5mm plug

Learn more about the Koss QZ-99

Warranty, Returns, And Additional Information

Customer Reviews of the Koss QZ-99

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  • Garrett .
  • 12/30/2014 10:34:39 PM
  • Tech Level: Average
  • Ownership: less than 1 day
  • Verified Owner

4 out of 5 eggsdang good headphones

Pros: the sound is very good, can't go wrong on the price and cancels noise pretty good too.

Cons: well i don't know about you guys but i have a big head, so even with the headphones extended out all the way they are a bit snug, but that should not be problem for most people.

Other Thoughts: I love koss you guys clearly know what you are doing and price your products well for any budget.

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  • Casey H.
  • 12/28/2014 10:43:05 AM
  • Tech Level: High
  • Ownership: 1 day to 1 week
  • Verified Owner

5 out of 5 eggsHefty!

Pros: First of all, be sure and read the "Features", they pretty much describe what Koss was designing these headphones for. With that, I have owned more than ten Koss headphones, over more than twenty years, and all I can say is... These are NOT your usual Koss headphones! In all the Koss headphones I have owned, and listened to, all of them were "designed" to be lighter, and pack a heavy bass "punch". Koss has even grown a following, on the basis that every headphone they have produced, has accentuated the bass. These are NOT that way. Koss, apparently, went with a radical change from their usual production, from lighter, extreme detail to sound quality, to, what can only be stated as, heavy, bulky, hefty, robust, and extreme sound dampening, at the cost of sound reproduction.

If you are buying these for sound, don't, I'll save you the time, and money. If, on the other hand, you are looking for something that can only be described as Aircraft Sound Noise Protection, that ALSO includes the ability to listen to music, then you got your item right here. These things are monsters compared to normal headphones. You'll realize that when you pick them up. When you get them around your ears, which is a feat in, as well as, of, itself, you are welcomed by the feeling of over-sized ear cup room (even for my ears), and the sound of silence. You actually get the feeling you stepped into a sound proof room. The cord is adequate, unless you are not used to coiled cords, and the stereo/mono switch, is placed in an acceptable distance. Where these "headphones" appear to be lacking, is, in their music production, and volume (see Cons). If you like hefty, heavy earphones, these are your ticket. If you are looking for serious "passive", and not "active", noise reduction, these will do it. If you want "DJ" style, or "Studio Monitor" headphones, you will seriously be dissappointed in these.

Cons: As stated above, these are not your "usual" Koss headphones. They aren't light, they aren't made for light duty, and they don't follow in the usual steps of Koss, when it comes to their bass reproduction. Quality is heavy duty though, they just lack in the sound. I plugged them into my computer, and had to throw not only the headphone volume to max, but also the sound players. I also had to add in Bass Boost, Headphone Expansion Volume, and Loudness Compensation, and even then, I still had to turn the volume on the headphones itself, to almost max. The drivers used in these headphones, I assume, must be made for serious Stereo "home" Amplifiers, because a computer just can't get the volume up high enough. Koss must have designed these headphones on the basis, that, if you have serious noise reduction from ambient room noise removed, you must not need to (honestly) have your music very loud (I guess). The volume control on the actual headphones is almost completely useless, if you are using a computer for listening (though I never got a chance to try them out on my Audiophile Stereo Home Amplifier. I didn't knock off any eggs for this music / loudness issue, as, I purchased these headphones for their noise reduction, and not so much, their ability to produce sound like normal headphones, or the usual "standards" of Koss headphones are known for.

Other Thoughts: These headphones come with a "Lifetime" warrenty, and considering how hefty, heavy, and robust, their construction is, I can't see anyone, who doesn't throw their earphones against the wall, on a daily basis, to have these earphones for at least a lifetime. These headphones are "designed" for long-term life, and usage (chances are, with the construction on these headphones, you may be giving them to your children. I also wouldn't hazzard to guess, they will be giving them to their children as well. These things are built pretty heavy-duty). If you are used to light-weight, or medium-weight headphones, these puppies will be anvils, compared. If you are looking for a great pair of headphones to do some "serious" music listening, you should pass on these. But, if you are like me, and want some "serious" noise reduction from ambient room noise, and have a nice luxury of being able to listen to some music, these will do the trick. Two last details, though, if you want to listen at high volume, don't get these if you are going to use a Personal Computer, Stereo Audio Amplifier recommended only. Lastly, even though the ambient noise reduction is pretty serious, I was able to hear, given I wasn't listening to any music with them on, my finger "snapping", not only at my face, but also at arms length. I didn't knock any eggs off for this either, as, I brought these headphones to work, which was their intended purpose for purchase, in an extremely noisey warehouse environment, and I would highly recommend, if you do the same, be warned you may not hear "emergency" sounds, horns, or "other" important warnings in your environment. Last word: These headphones do what they advertise, but at the sacrifice of high quality music listening pleasure.

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  • jan d.
  • 12/23/2014 9:22:47 AM
  • Tech Level: Average
  • Ownership: 1 week to 1 month
  • Verified Owner

5 out of 5 eggs

Pros: Got these as a gift for my Husband. He says the sound, is great and they are comfortable to use. Primary use is for watching videos.

Cons: So far, no problems at all

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  • Jeremy T.
  • 10/16/2014 2:00:10 PM
  • Tech Level: Somewhat High
  • Ownership: less than 1 day
  • Verified Owner

4 out of 5 eggsFits what I wanted

Pros: Great noise cancelling considering the price. Much better than any other noise cancelling headset I have tried. My office environment gets loud enough to be a serious distraction, and these block out all background noise. These things work as good as the hearing protection when I worked in an industrial print factory.

the headphones are large enough to fit completely over the my ears.

Cons: The weight of these is slightly heavier, but still similar to hearing protection I used to wear in a factory. That means they are much heavier than any other music only headphones I have worn.

These things are mostly made for settings where you need sound while in a loud environment, not specifically for great music quality. There are not separate speakers for bass as on some medium to high quality music headphones so the bass suffers for music listening. that being said, the sound isn't bad.

But if you do your reading, you don't buy these for top of the line sound, but for noise cancellation.

Other Thoughts: Some notes from my old days working with industrial hearing protection ... in the morning the headset will be cold, and your head will be warm. As the headset warms up, it will create some air pressure next to your ear that is uncomfortable. To relieve, just occasionally break the seal next to your skin by briefly taking them off to let in some air until they warm up. They dont seem as uncomfortable to me as others seem to indicate, but then I am used to this kind of thing.

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  • Sergey G.
  • 10/8/2014 9:22:16 AM
  • Tech Level: Average
  • Ownership: 1 day to 1 week

2 out of 5 eggsits so uncomfortable!!! WOW!

Pros: Cheap. Fast Shipping. Sound is ok.

Cons: Super uncomfortable... did they test them on bricks? uncomfortable from the second you put them on. Start to really hurt after about 10 minutes. Cannot have them on more than 30 minutes. Its ridiculousness.

Other Thoughts: honestly, the fact that they are so uncomfortable, overshadows all other good qualities..

1 out of 2 people found this review helpful. Did you? Yes No

  • James E.
  • 8/6/2014 10:11:04 PM
  • Tech Level: High
  • Ownership: 1 month to 1 year
  • Verified Owner

2 out of 5 eggsUncomfortable

Pros: Good sound.
Decent isolation.
Durable construction.

Cons: These headphones are uncomfortably tight. It's like putting your head in a vice.

Other Thoughts: I had another set from the same brand that I was happy with but they wore out after lots of use over several years. I was happy enough with them that I decided to stick with the brand.

I don't know if I just picked a bad model or what but I'm not too happy with my new set.

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  • Irving S.
  • 1/20/2014 9:50:34 AM
  • Tech Level: High
  • Ownership: 1 day to 1 week

5 out of 5 eggsBest Lower Quality Headphoens Money can Buy

Pros: This is a very durable, very sturdy feeling headphone. The price is a wee bit high but the build quality feels very good so I can't complain. The headband over the head comes with a thicker pad. When you put this on your head, there is no discomfort that comes from the top of your head. It's worth mentioning that the side of your head does some of the work to keep the headphones up.

Sound quality is meh, but so are most headphones. There's nothing you can do about "Meh" headphones no matter where you go. These are just as good as any Beats headphones, which are grossly overpriced for the quality that they give.

Cons: It's not SUPER comfortable. It's certainly a tighter fit, but usage after a very long time is still very good. Basically they feel the same throughout the day. More of a preference thing than a con.

Other Thoughts: If you want a GOOD pair of "Meh" quality headphones, this is a great buy. But these are a bit tight on your head so you may want to "try before you buy" if you can. I'm perfectly fine with a tighter fit.

1 out of 1 people found this review helpful. Did you? Yes No

  • RYAN H.
  • 11/6/2013 8:25:00 PM
  • Tech Level: Average
  • Ownership: 1 day to 1 week
  • Verified Owner

2 out of 5 eggsMaybe I just have a weak neck

Pros: Love the length of the chord, all of my previous headphone chords would get caught under chair wheels.

Cons: It's quite heavy. According to the cost calculator when I tried to return it, they are 4 lbs. As pretty much everyone has mentioned, they're tuned to the mids so don't expect to get the kind of range you need for working with music or sound effects. One reviewer claims that it cancelled out the sound of grinding metal but I can still hear my roommates talking through a closed door with music playing.

Other Thoughts: I was willing to lose $20 to return these but was unable to pay for the return label. (keep getting a CVV2 error)

1 out of 1 people found this review helpful. Did you? Yes No

  • Kyle C.
  • 10/19/2013 10:47:14 AM
  • Tech Level: High
  • Ownership: more than 1 year
  • Verified Owner

4 out of 5 eggs

Pros: Durable with decent sound. I wear them about 7-9hours a day during my job. They do after a bit start to hurt the ear but I can usually reposition them to fix that. The volume knob is handy, as I can turn it down when someone is speaking. The noise canceling part works well. With moderate volume, it cuts out the sounds of grinding on metal. Also works well for cutting the grass.

Cons: The bass production is lacking, even with adjusting of equalizer on my ipod. I had an older model of Koss that I liked better. Also had Sennheiser ear buds that had more bass. My cat chewed through both cords, hence why I now have these.

Other Thoughts: The padding on the head band could be better. As mentioned above, I wear them a lot. At times I'll hang them around my neck to give my ears a break. This isn't the most comfortable thing to do, but helps if you shorten them up all the way.

I saw a few people mentioned the cord not being long enough. I fail to see this issue. I put my ipod in the back pocket and have to wrap up a good 12in of cord and put in my front pocket. For home use, maybe, but I have an extension cord for that.

All in all I have put a ton of hours through these and got my money's worth out of them. However, I'm looking for something new as I want to hear bass in my music.

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  • Clayton B.
  • 7/4/2013 8:32:15 AM
  • Tech Level: Average
  • Ownership: 1 day to 1 week
  • Verified Owner

5 out of 5 eggs

Pros: Sound is great, watched a James Bond movie wearing them and I couldn't be happier. I thought that they fit pretty comfortably too. I would definitely buy them again.

Cons: wish it came with a case

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