I've had my iSine 20 for a while now so I thought I'd post some impressions. For the record, these are only my opinions. At home, my reference headphones are Abyss with a Chord Dave and WA-5LE with Japanese tubes. In noisy environments I use an Audeze LCD-XC with Chord Mojo. I admit I love Rob Watt's DAC designs and am looking forward to the Hugo 2 for headphone listening.
First of all, I completely disagree with those who've said that an ear canal seal with the iSine 20 is a bad idea. These headphones are more forgiving of resonance, etc., because of their semi-open design, but they absolutely sound better with a nice, easy/light seal not to deep in the canal. Better bass, better isolation, better sound, and it's not subtle. For me the medium tips did it. Small tips went to deep and were bass light. Fat tips formed too tight a seal. Medium were perfect. I recommend moving the tips in and out a bit during a track and you'll know when you're there. Find the right fit for your ear and make a light seal. It's just better.
For these I use an iPhone 7 plus as a source, mostly Tidal HiFi and HF Player high bitrate content. I like to start with well-recorded accoustic recordings because I know what they're supposed to sound like and beyond that I use the Abyss as my reference for what is the best possible bass on a headphone (which only sound speaker-like IMO on the Abyss). I don't bother listening to the direct output of the iPhone - just comparing Cipher with Mojo.
Cipher is an engaging sound in a convenient package. I don't like the peak at 4KHz at all, so I've used someone else's EQ settings on this thread to reduce primarily the 4KHz bump and some attenuation a little below and a little above. It's a fun sound, but to me it's a bit fatiguing and not as natural and analog/organic as I'm used to. I enjoy it, it's convenient, but you can do better with these headphones.
I admit, I don't like to use EQ. For me the iSine 20 sound spectacular right out of the Chord Mojo. The bass is dramatically better defined and more if it - which is strange because I thought Cipher boosted this with PEQ. It's much more natural sounding. It's got plenty of bass, and quality bass. iSine 20 with the Mojo is not only less fatiguing, it's just more realistic on recordings where natural sound is expected. While the Cipher is a fun sound, the iSine 20 properly fit with the Mojo is pure magic. Again it's not subtle. Getting it fit right is critical to being able to hear its full potential and differentiate between Cipher and Mojo.
So - take time with the tips and make the right, light seal. The iSines are better with it and I don't understand the observations of those who have written differing opinions suggesting deep insertion and little to no seal.
For me, analog with Mojo is preferable to Cipher all day long. It's more musical and more natural, better more bass, and just more engaging. In my opinion. That said, I'm perfectly happy to enjoy Cipher and enjoy playing with EQ when I don't bring the Mojo, which honestly is almost never.