I have been using HD600, HD25, DT770, MDR7506 and 7509 for years... some 25 years plus. I understand how each set fits, sounds and translates so when I got the Audix A150, I wanted to understand what the meant by linear and reference. Out of the box I actually thought they had a bass boost and the highs were veiled, BUT upon further listening I began to understand their sound differently. I've only seen 3 online professional reviews, no YouTube influencer or forum reviews. I pretty much bought these blind. No in-store testing just my ears and the 150s. I did a very unique test: I went on Sonarworks website and plugged in my 600s and 770s and A/B'd their "flat"/linear curve software with the 150s. No, Sonarworks doesn't have the 150s tested yet, however, I would try the 600s flat then gain match the 150s without the software then the 770s with the software and the 150s without. WOW!!! These are not bass light or heavy but pronounced. Not an extra sense, but they bump! It can be hard to get out of the way of the mids and the high frequencies when the bass is even, but every frequency seems balanced. When compared to the HD 600s with the sonar effect and the Audix without it it was almost on point, besides they didn't sound as open where the higher frequencies are somewhat more forward. I did the same test with the 770s and it seems the 150s had slightly more bass, everything else seen balanced. The Beyers still sounded more open so my assumption is the 150 has a smaller sound stage yet because of its linear qualities frequencies can be masked. It's not a high resolution sound - meaning the highs are attenuated/colored; the mids aren't forward but not dipped. Because the low mids are present, it makes the high mid and high frequencies seem veiled though clear. After realizing I had my glasses on, I conducted the test again and these are my results:DT770 and 150s: Surprisingly the sound is dead on! The bass is balanced, mids are present and highs are not too crisp. The entire frequency sounds linear according to this Sonarworks test to my ears.HD600: 150's Kick drum bass "knocks" more pronounced, where the 600 is defined, both are good. The 150 I "feel" the 600 I "hear." Mids seem flat though 600s seem more natural and 150s seem more clinically flat which can mask other frequencies and can be useful. Again the highs on the 600 seem open and detailed where the 150 highs are "there" , not dull, not "airy", just present. The mids can be described as creamy, thick and rich! I believe due to the fact they're not bass light like the 600s. Overall the 150s are a very useful tool. I got used to them very quickly. Listening to commercially produced music, I can hear a major difference between well produced reference tracks and everything else. I can hear the types reverb spaces and separation. The 150s have excellent imagery. These cans are honest and unforgiving. When I listen to my own music with them, I now hear how I can use 3 dimensional space in my mixes better. I hope this helps your decision to try these amazing headphones. I did a very unconventional trial, but I think may be affective, I suggest you do the same. The reason for the 4 stars, is the build quality is all plastic, which makes it very light, but questions its build quality. With that said, I do believe that the A150 headphones will serve me well for some time and I look forward to many accurate mix references as u should too.