I have my moondrop s8 for a couple of days now. I experienced definately a learning curve how to fit them correctly and what tips to use.
In the beginning days I was irritated about the fully closed housing.
Most of my other in-ears are vented, or have very narrow nozzles. The resulting suction and feeling of a full seal wasn't all that pleasent so I tried different sizes and ear tips and settled on a shallow fit with medium sized tips. Although the sound being very good, there was some splashy brightness to it.
I suspectd it to be the upper midrange - I was wrong.
Using them for a couple of hours I noticed a hotspot was forming. So i tried to figure out how to get rid of the hotspot and I noticed the in-ears were far from sitting flush within my ears. The lower part sticking out to much. So I went for the small tips and tried to fit them deeper until I reach a flush fit. The hotspot went away and the sound changed considerably. Bass is fuller and the splashyness went away, everything sounding more relaxed now. With deep fit though there is another issue which can change the sound.
You have to be carefull not overpressurizing your ear canal when inserting them. I figured out the best practise is to open the mouth slightly when inserting. Overpressure tends to congest the sound, losing volume and bass presence.
One problem is still present which is a drawback of fully sealed in ears. The inner volume of your ear canals change when moving your head or your jaw. Stretching or squeezing your ear canals.Though there is no way for the enclosed system to depressurize This does change the perception of sound to some extend depending on your head rotation.
I hope it's not boring read everybody figured out already.
Giving it some more days I will post more in depth impressions of the sound quality I'm hearing