I wouldn't really pay attention to Rtings Soundstage scores as they come up with their own methodology, but yes the HD600 is known for not having the largest Soundstage as an open back

This gets really deep and there's been a lot of research on it. In short, Yes if two pairs of headphones had an identical Frequency response at your eardrum they would sound the same (ignoring factors like comfort, ambient noise, how the pads feel on your ears which all affect how we perceive sound).

The thing is, it's virtually impossible to make two pairs of headphones have the exact same Frequency response at your ear. Even from two models of the same headphones there will be differences you can't EQ in.

The frequency response graph you see from measurments is best used for comparisons, but it doesn't represent the frequency response it will have in your own head, and even headphones that measure very close on a rig, can have large differences in the frequency response when it's on your head due to difference acoustic impedance.

The best way to look at it is, yes everything does come back to frequency response in headphones, but it's just the end result and not something you can EQ one pair of headphones to match another. So in a way, "Technicalities" does exist as a part of frequency response, and you need to listen to them to get the full picture.

Yeah the cp145 is a little thicker around the nozzle. The 155 is thinner there and shaped a little more tapered. I find them more comfortable myself, but everyone is different

Yeah the EDA silver is really a good cheap IEM

The tips have thinner silicone walls and also much thinner around the part that goes on the nozzle. That, combined with the more tapered design, allows it to mold and fit deeper and more secure, compared to the stock tips which are more rounded and bulky with stiffer silicone. The nozel on its own isn't too big for most ears, it's just with the thick silicone layered on top it gets too big

If anyone has fit issues, Spinfit CP155 tips solve that issue and fit completely in my smaller ears

Exaggerating the positives and negatives between headphones and their differences to prove a point or push a preference really isn't good for the audio hobby. Sadly many fall into this (I have as well)

Hoping the community continues to improve

For me the biggest difference between headphones and earphones is the interaction with your pinna and HRTF. Headphones directly have the sound interact with your pinna and changes the Frequency response to how you're used to hearing, where as IEMs Bypass your pinna and use an approximation of an average pinna gain.

That said, yes earphones are very good, and there is a very noticeable difference between a $50 pair and a $300 pair.

My wired IEM earphones are $320 and there's quite a difference in sound presentation with that and a pair of over ear headphones that cost the same. Both excell in their own ways.

Our perception of sound is also heavily influenced by other factors. Fit, space, how much sound is let through. There's so many factors that change not only the frequency response, but also our perception of sound, which makes no pair of headphones, even of the same model sound exactly the same

MP3 has a stigma in some places because old mp3 was bad. But modern MP3 320kbps is good enough, most people won't be able to tell it from lossless in a blind test.

Get whatever headphones you'd like to

That's pretty much what the Focal Elex is right?

So Harman, it's not just a crowd sourced target based on an average preference.

The target was first derived from the frequency response of flat speakers, in a typical room, recorded on a head and torso simulator. The bass boost and downward slope is what we expect to hear from good speakers in a good room.

From that, there was group testing done to tweak things by a few dB, and the Harman research says to adjust the bass level less or more to your preference.

The target itself is meant to be a reference point, but not necessarily something to adear to exactly, especially in the treble since the target is very much smoothed and doesn't represent the peaks and dips that headphones or speakers can have at our eardrums.

As for what to EQ to, we all hear differently and have a unique HRTF. This means what you see on a frequency response graph will not represent what your hear, or the frequency response at your own eardrum (mostly past 3khz), so EQ to your own preference

Yes. While most things that people consider technical performance is hard to pinpoint and not something you can simply EQ in most of the time, you can affect how headphones sound quite drastically with EQ. Usually in the case of headphones that may sound "muddy or low resolution". Changing the sound signature with EQ can make them sound "detailed" or "faster" if we're going by those types of terms.

To be fair, at that price I'd probably go for Sony, Samsung, or airpods pro as well

https://crinacle.com/graphs/iems/graphtool/?share=Harman_IE_2019_v2_Target,MW07_Plus