I'm pasting here the feedback I gave to another member 6 months ago. In short: I don't use the IE800 since I have the Merlin.
- I look for a musical and living experience. I don't really care for neutral.
- Both models have a similar, V-shaped signature
- Both models have boosted bass, however the bass on the IE800 is more powerful or dominant. It's really hitting hard and has a strong mid-bass hump. Bass on the Merlin is more deep-bass focused, so it does not hit as hard and does not have as much thump. However it results in a more natural sound; it was accurately described as "acting as a third party" (sometime I have the impression it is located a bit further the musicians). IE800 has the more "club-feeling" (*** edit: bass quantity varies with your DAP: lots with AK120, less with DX50)
- Vocal takes the center stage on the Merlin (it's actually a mid-focused monitor ***edit: now I find the mids a bit recessed) while it's a bit recessed on the IE800, where the bass steals the show. Both mids are liquid and sensual, but clearer on IE800
- Treble is sparkly on both, but it's a bit thin, splashy (think razor-shaped) on the IE800 and more forward on the Merlin
- Both have great soundstage. Merlin has the largest, with great height
- IE800 is more coherent and has a nicer presentation overall. With the Merlin I sometimes feel the band plays in an empty concert hall (***edit: not anymore). IE800 is a bit more intimate
I spend most of my time with the Merlin which has better technical skills (esp. instrument separation) and delivers better performance across bass-mids-highs , but I was stunned by the IE800 when I first heard it. Maybe because I never heard anything better at that time.
Both are somewhat relaxed, if you want the feeling that someone put speakers 30cm near your ears, try JH13/16.
I recommend the Merlin for overall SQ/comfort. It pairs well with AK120.