I find this conversation amazing. Would you explain having a narrow sound? Humans have an auditory range (what they can hear) from approximately 15 Hz to 20 kHz? You state that the headphones are noisy with power metal? My hypothesis would be that what you describe as noisy is actually detail and you are listening to music that is distorted but that doesn't sound very good on accurate and detailed headphones. I have listened to metal very little. I mainly listen to jazz and classical and some country/rock/popular. I found as I moved from a $2,000 stereo system to a $5,000 system to a $30,000 system (I didn't pay nearly that much for the 30k system since I bought the preamp and power amp used from a friend) that rock I had liked (e.g. the Stones) was really bad sounding music. Even remastered, a lot of the old rock was done by poor musicians and the recordings are not very good. In contrast, the jazz (especially Blue Note) recorded even in the 50's is brilliant.
I am not arguing that the M50's are great although I like them pretty well. My favorite phones are probably my modified
Denon AH-D2000
with Lawton cups and sheepskin pads. I also like my AKG-271, my HD650, my DT-880's, my DT-990's etc. I am leaving out 3 or 4 other sets of cans that I also like. I would even like my AKG-701's if they didn't hurt my head. The M50's get good (excellent for the price) reviews on the Headphone Review site which I think is a good source of information (the reviewers are screened). The M50's also have a good rating on Amazon with over 650 reviews which indicates that the average user likes them pretty well.
One of my other hobbies is shooting. With guns there are objective measurements. Will a rifle shoot to 1 or 2 MOA at hundred meters or what is he velocity of round at a 1000 meters (actually it is usually the energy and not just the velocity that is debated). I used to ride sports bikes and they had objective measures for things like speed in the quarter mile and braking distance etc. Although even there I saw people argue that a 600 cc bike could not possibly have a top speed of 162 mph because their 10-year old 1000 cc bike would only do 145 mph. Obviously those individuals didn't realize that the (then) modern 600 cc bike produced 100 hp at the rear wheel and had a wet weight of 400 pounds while their old liter bike produced 85 hp and weighed 650 dry. Of course now the 600 cc bikes are producing 120 hp! Progress!
My point is that all of our reviews of headphones are subjective. My hearing compared to some of my audiophile friends is not great. I like warm phones with lots of detail. I like precise solid state amps or tubes depending on my music and my mood. Probably most of the phones over $100 produced by Denon, AT, Senn, Beyerdynamics, AKG, etc.reproduce music more accurately than most of us can appreciate. We may like one set better than the others but that may be because of our hearing or it is just what we like. Some people prefer phones (and speakers) that have a different balance (or that are even distorted).
Are the M-50's better than the AKG-240's, I don't know. The HD-280's might be a better buy. I think the HD-280's are a great buy but I don' use mine much because they are tight on my ears.
Anyway, I think for someone who wants to start listening to earphones and who doesn't have a ton of money, the M50's are a decent buy. One of my friends told me the other day that he had just purchased a new power filter (for the AC current) for his stereo system. The filter cost $2000 and his system probably cost him 50K. He claimed that now the resolution was so much better. He does have great ears but I don't think adding a $2k filter to my system would make a bit of difference in what I hear. This stuff with earphones is not science, it is just opinion.
