Thanks everyone! It's a pleasure to review great products!
I've been AT fans for many years, though also often disappointed by their IEMs. But this time AT done it right, and I'm so glad they did
IM50 and IM70 for their sound quality and build quality, to me simply a no brainer... those 2 are really giant killers.
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Wow, you really went to town with that review - excellent work! I'm surprised you describe the 50 as bassier than the 70; so far I've heard the opposite. I have the 50s and really enjoy them, except that they can be a bit uncomfortable at times.
Wow interesting! What player you use for IM50? After doing this review, I'm not so surprised with different opinion
i wonder which will fit the music i listen to.. Justin Timberlake type or avenged sevefold
I don't have the album, but for pop vocal, IM50 & IM70 would be my choice.
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Really impressed with your work! Almost nobody discusses output impedance and it's quite relevant to how our gear sounds. But why do some of the earphones sound good regardless of source? Doesn't this defy the rule of damping factor (e.g. IM50 and 70 have 10 ohms Input Z, yet 4 of 9 players/amps you tested have Output Z greater than 1.25, which would have damping factor <8)
Also surprised that you found the IM50 and 70 neutral (as you said in one of your opening paragraphs, "I consider all of them, even with their own unique sound characteristic, more or less sound fairly neutral."). Did you not think they were very bassy? And re: IM50 vs IM70, did you find the bass and treble more disconnected from each other?
Sorry for the confusion, maybe I have a rather wide tolerant for what I consider as neutral sounding. IM50 & IM70, have good level of bass, and not very bassy (especially for bass head) if we have adapted / used to, with their sound signature. And their bass, to me integrates quite well with the rest of the spectrum, I don't feel the bass is disconnected. Maybe on TDK IE800, I felt the low bass a bit disconnected, but not on IM50 & IM70. Anyway, the dual symphonic drive are not 2 ways driver, they are still 1 way. Both works together for the whole frequency spectrum. The dual design is to improve overall handling power to move the air, to reduce distortion.
If we use to hear clear analytical sounding earphone, and suddenly change to IM50 for example, for a moment we will feel IM50 is very bassy. What I've learnt so far, is our brain adapting with the sound signature we use often. For example, I use Beyerdynamic T1 often, one of my favorite. Last year, when I bought Yamaha EPH-100, and started to like it, especially with the kind of Stockfisch recordings, after a few days with EPH-100, and I go back to T1, I felt T1 was too bright for me... I felt very strange. Then I learnt that our brain keep adapting to the earphone and headphone that we use often. When I get used to T1 again, I felt EPH-100 sounds a bit too dark.
Regarding output impedance, let me share my experienced with the very high output impedance of Hifimediy UAE23 USB DAC:
http://www.head-fi.org/t/678798/hifimediy-sabre-usb-dac-uae23-and-audioquest-dragonfly-brief-comparison
UAE23 with around 200 ohms output impedance was sounds ok with many dynamic drivers. And I didn't have much problem with their dynamic which supposed to be poor due to the low damping factor caused by high Out Z. Until I tried them with BA earphones... I can say all BA driver earphones sounds terrible on UAE23. What I'm trying to say is, maybe our ears are much more sensitive to tonal balance rather than damping factor. I know that UAE23 was not very punchy, but I've enjoyed them for quite a while with my JVC HA-FXD80 (dynamic), until I bought Dragonfly. Knowing their 200 ohms Out Z, it is strange enough how they sounds pretty good with the dynamic driver.
As why some earphones sound good regardless the source / amp, my guess is because they have a more linear impedance over the whole frequency spectrum.
But as why IM01 sounds best with rather high impedance AK100 (20 ohms), that also puzzles me...