Do these benefit from burn-in?
Yes they do. I just got a pair of HAFX34 which is the same set just different model # and after removing the paper filter they improved dramatically over the next 4 hours.
I didn't stuff with foam yet but I'll do that on another pair so I can do a head to head test.
I had to burn-in my HARX-900 around 150 hours to hear a major improvement.
One thing I found is that the stock foam tips did not work for me at all.
I used a pair of large size silicone tips that come with Ultimate Ears sets.
Now I get a nice seal and the low end is VERY impressive.
Usually in the under $20 price range there isn't very clear and pronounced top end that presents well recorded music with astonishing detail with a nice bottom end thats sufficient for Dubstep and Electronic music with none of the usual bloated upper bass that plagues so many budget IEMs.
I can listen to anything on these IEMs and they work as monitors/earplugs when playing drums.
I have pair of Ultimate Ears Super.Fi 4 which sound very sterile.....and these are better to my ears.
And the best part....I found these at a Job Lot and the clerk sold me all the pairs for $2 each.
