I realized I never wrote down my impressions and they are loong overdue. So while this isn't a full review, I've been listening to the Merlin a lot the past couple days and I've just got to give them some love here on head-fi.
I ordered through Stephen Guo of custom-iem.com and the turnaround time was 20 days (including weekends) from when they received my impressions to when they were shipped off. Unfortunately, I needed a refit so back to China they went. This time, the turnaround period was 26 days (including weekends) which is still much faster than people in the group buy. I thought about it, and realized that although I paid almost 2 months after people in the UM Global group buy and sent in my impressions a couple weeks after UM got theirs, I received my refitted Merlin before many people from the group buy got anything back.. So I'm quite happy with the turnaround times and Stephen was a pleasure to deal with.
Starting with the build quality. the Merlin has one of the best, if not the best build quality I have seen. I don't see any bubbles in the shell and the faceplate turned out exactly the way I wanted it. I love how my artwork "floats" above the beautiful titanium plates when look at them from the right angle; they did an excellent job.
Before I get to the sound, let me just say that I had very high expectations for the Merlin with them being my most expensive pair of IEMs at the time. I actually had to tell myself to lower my expectations in case I get disappointed with what I hear. When I finally plugged them in and put on my favorite track, I was blown away by what I was hearing. They are exactly what I was looking for. People who choose the Merlin usually have one thing in common, we're looking for boosted bass from the hybrid design. As advertised, the Merlin has bass that extends very deep into the sub bass, lots of it too. It has more sub bass than mid bass and can really make a track rumble. It also has great texture and detail, reminding me highly of the FX700 but with more control and refinement. The Merlin bass is super clean and has better speed than I anticipated. I think what really "made" the bass for me is how organic and natural the bass sounds.
As usually the case with my preferred sound, the "V-shaped sound", mids are always recessed. I was very happy to find that the Merlin's mids are not. Although I don't find them to be more forward than the bass, vocals are certainly a little forward. They are lush and quite intimate actually. There is also a lot of emotion and great detail. So while I feel the bass still has a stronger presence in the spectrum, the mids are still beautiful and upfront - a very pleasant surprise. Now to the treble. I'm generally quite sensitive to the higher frequencies and can find a bright pair of phone fatiguing fast. The treble on the Merlin never gave me that feeling despite having crisp highs and lots of sparkle. Cymbals sound just right with no harshness and there is lots of detail and clarity in the top end.
What can really make or break a pair of phones for me is the soundstage. I highly enjoy a big spacious soundstage and once again, the Merlin did not disappoint. The stage is very wide with lots of depth and a huge amount of space. There is still excellent placement of instruments and performers despite the large amount of space between them.
Overall, I love my Merlin. I had a very positive experience with UM and my final product came out looking exactly the way I wanted it to be. After hearing the Merlin, I didn't and still don't want to hear any of my ~20 pairs of universals that I have in possession anymore because they simply can't compare. For people in North America, it's too bad that their lab is located in China as it accounts for a longer turnaround period and more shipping charges. But in my opinion, if the Merlin has the sound sig you're looking for, they are worth the wait.
Pictures in the first post but here's an extra one.