[10 Hz to 20 kHz] Great sound, lightweight.

[Closed-Back] As a user of Bose, Beats, and Sennheiser products, understand the weight of my words when I say these headphones are above and beyond the best pair I have ever used. For a fraction of the price of other quality headphones the Portapros seem to have no limit when it comes to frequency, searing synthesizers and thumping base both come out in absolute clarity at any volume level. As well as reaching the peaks and valleys with ease, I have not noticed any rattling of the headphones at any frequency, despite its light weight. Speaking of the weight, the portability of the headphones show ingenious design. Durable and collapsible, I was very pleased to find how easily I could take the Portapros around without fear of damaging them. I can think of only two setbacks to the headphones. First, the 3.5mm jack is smaller and appears to be somewhat more delicate than the one shown in the picture. Second, there was no mobile headset available, which would have been much preferred, when you take smartphones into consideration. Otherwise, I doubt I could find such a spectacular pair of headphones for such a remarkable price. Buy them!

[Closed-Back] As a user of Bose, Beats, and Sennheiser products, understand the weight of my words when I say these headphones are above and beyond the best pair I have ever used. For a fraction of the price of other quality headphones the Portapros seem to have no limit when it comes to frequency, searing synthesizers and thumping base both come out in absolute clarity at any volume level. As well as reaching the peaks and valleys with ease, I have not noticed any rattling of the headphones at any frequency, despite its light weight. Speaking of the weight, the portability of the headphones show ingenious design. Durable and collapsible, I was very pleased to find how easily I could take the Portapros around without fear of damaging them. I can think of only two setbacks to the headphones. First, the 3.5mm jack is smaller and appears to be somewhat more delicate than the one shown in the picture. Second, there was no mobile headset available, which would have been much preferred, when you take smartphones into consideration. Otherwise, I doubt I could find such a spectacular pair of headphones for such a remarkable price. Buy them!

[32 Ohms] The ONLY problem with this headphone is that if you have long hair it can snag your hair. I keep my hair low so that's not an issue. This headphone rocks!

[Closed-Back] Excellent sound and it comes with volume control so it is good for maintaining sound quality

[32 Ohms] These are for recreational use, like from a laptop, cell, or iPod. They appear flimsy, and you might think you wasted your money when you first get them out of the box, but you would be wrong. They are solid and I am sure they will last a long time. The sound is big and full, with crisp highs and solid lows. I would even feel comfortable making a first draft mix on these, if I was in a pinch. Some people talk about getting your hair stuck in them, but that hasn't happened to me yet. They fold up small and I have no problem finding space for them in my bag. I don't usually listen to music during my workouts, so I did not include their performance in my review. Definitely worth the price - impressive for a pair of headphones that have remained unchanged since 1984!

[4' / 1.2 m] Great dynamic range. I heard my mp3 files play sounds that I did not hear on my Sony headphones. The phones are light weight and they fold up into a small pouch for storage. Given the fold-ability, the wires may get stress so I'm being careful with it. Other than that I'm happy with these phones as I have been with all Koss Products I've owned including the Pro 4AA's I originally bought many years ago.

[Stereo] Use to track and playback my acoustic/electric basses, when recording. Also great for practicing while watching TV (go Warriors!) Seriously, the best part about these headphones is how light they are, how easy it is to hear other things around you when you need to, and the sound of the bass. Designed to be bass heavy so you can wear them loosely and still get a full sound. My favorite headphones of ALL TIME. Also, LIFETIME GUARANTEE IS FOR REAL. (the only problem is after a few years of falling asleep in front of the TV, you can strain the connection at the earpiece.) I've sent back two different pairs of them in the last TWENTY YEARS. (bought my first in 1996) Best price, in this case, is the best product. Buy them. You will not regret it... :-)

[Dynamic] I purchased these at the B&H store in person back in March. My other headphones are AKG K271s (also purchased from B&H in 2004) and Shure E4C IEMs. While the sound quality of the PortaPros doesn't match those of $200 head/earphones, they fill a gap in my lineup that needed to be filled. They have surprisingly good bass, especially from underpowered sound sources like smartphones and laptop headphone jacks. They allow me to wear them and hear my surroundings, which is what I purchased them for. I didn't want to get run over crossing the street in NYC while wearing my E4Cs. Downsides, of course, include noise leakage. They aren't the clearest sound-wise, but they're leagues ahead of what other $30-range head/earphones I've tried. The headband came apart once and it took me a little while to figure out how to reassemble it, but it doesn't appear that I've actually broken anything. If I had, I would have taken comfort in their lifetime, no questions asked warranty that I only heard about after I had purchased them. Highly recommended.

[Dynamic] I purchased these at the B&H store in person back in March. My other headphones are AKG K271s (also purchased from B&H in 2004) and Shure E4C IEMs. While the sound quality of the PortaPros doesn't match those of $200 head/earphones, they fill a gap in my lineup that needed to be filled. They have surprisingly good bass, especially from underpowered sound sources like smartphones and laptop headphone jacks. They allow me to wear them and hear my surroundings, which is what I purchased them for. I didn't want to get run over crossing the street in NYC while wearing my E4Cs. Downsides, of course, include noise leakage. They aren't the clearest sound-wise, but they're leagues ahead of what other $30-range head/earphones I've tried. The headband came apart once and it took me a little while to figure out how to reassemble it, but it doesn't appear that I've actually broken anything. If I had, I would have taken comfort in their lifetime, no questions asked warranty that I only heard about after I had purchased them. Highly recommended.