Instruct: Classify the given Amazon review into positive or negative sentiment.
Query: Koss Porta Pro's- clean sounding!

I have had these headphones now for about two years, nice quality of materials and sound, they look some what different then conventional style, they are comfortable once placed on your head properly. Please treat them kindly and give them about 30-40 hours of break in time before passing judgment on their sound quality, after that they will reward you with a positive listening experience. I compare there sound to be very similar to the Sennheiser PX 100-2 headphones with a slightly more emphasis on the Midrange versus a slightly more Bass on the Sennheisers. If you like good clean revealing sound with a little less emphasis on Bass you will enjoy these Koss Porta Pro's, take my word for it! Please see my other review of the Sennheiser PX 100-2's.