Looking at your pictures, I realized I absolutely adore everything about this set... except the tuning (it's not an all-rounder). I mean, in comparison, the Monarch Mk III is so disappointing in terms of its presentation, and it costs how much, I'm sorry? ... I guess this one really pushes my buttons, it's so tasteful. Good job, @HiByMusic and FAudio, nonetheless, this one's a beauty. Despite it not being my cup of tea tuning-wise, I'm happy that such tuning experiments still exist, it shows that people have still have original ideas and not everything is done purely for guaranteed profit.

Thanks a lot for the review!
I evaluate IEM's with this type of tuning in the mid bass, lower mids, and higher mids preferrably by listening to specific violins who's sound, timbre, and unique standing waves I know in and out. In general, violins are IMHO the perfect instrument for these frequencies since their natural FQ ranges from ~200 Hz up to 3500 Hz (with the highest artificial harmonics even up to 4,700 Hz), so they're my tool of choice.
So far, what you wrote keeps me thinking positive and in anticipation, my DaVinci should arrive next week... finger's crossed.

@droid23 Thanks for your thoughtful response! I agree, violins are excellent for judging sound quality due to their wide frequency range and distinctive timbre. I also enjoy using them to test IEMs, particularly in classical music, and I'm a big fan of Lindsey Stirling. Additionally, I have a special fondness for cellos—I'd recommend trying out some cello pieces with the DaVinci; it sounds incredible. I'm glad my review has you feeling positive and excited. Fingers crossed that your DaVinci lives up to your expectations! Looking forward to hearing your thoughts once they arrive.

@vietzerg To me, the DaVinci has both more bass quantity and superior bass quality compared to the IE600. The DaVinci’s bass offers greater slam, impact, punchiness, and texture, with more detail. It also has better bass definition, clarity, and separation. Additionally, the bass is more tactile, allowing me to feel it as well as hear it most of the time. This is my opinion based on my preferences. IE600 is still a great IEM.

"these IEMs require powerful sources. When paired with the right equipment, the Quattro can deliver an outstanding audio performance. For example, when I change the source of DAC from RU6 to Fiio Q5"

That is not a matter of going from a weak power output to a higher one. But the difference of going from a warm soft mushy r-2r source to an overly incisive D/S dac.

Quattro needs that leading edge incisiveness help of a D/s dac like the akm in your Fiio Q5. Fiio Q7 with its ESS dac also does this as well.

Love it when a reviewer is passionate and articulate. Well done

Great review! Thanks for sharing!

Great review @emdeevee
The Voltage sound awesome, I bet I would love it also. Sounds like Penon have really refined their sound here