Comparison.

The comparison was done using Indigo with a stock cable, Xelastec stock eartips, and LPGT source; volume matched in every comparison.

Indigo vs FiR Audio M4 – Indigo soundstage is a little bit wider, perhaps due to Indigo having more air in upper frequencies which gives its soundstage a more open and expanded width.  Their bass, from sub-bass rumble to mid-bass impact, has a lot of similarities, not exactly identical, but it is very close in weight and presence.  Upper mids are very similar as well, making vocals sound natural and detailed, and lower mids are not too far off either, though, overall, I found M4 mids to have a little more coloring and Indigo mids to have a little more transparency.  Both have energetic highs, but Indigo adds more air and has a little better treble extension.

Indigo vs 64 Audio Trio – Another interesting comparison since original MKII was closer in tuning to Trio.  But now the tuning gap is a little wider.  The first thing you notice is a V-shaped tuning of Trio vs more balanced tuning of Indigo.  Soundstage expansion is close, maybe with Indigo being just a little bit wider.  Both have elevated DD bass with a deep sub-bass rumble and healthy mid-bass slam, but Trio scales up in quantity just a little higher, which could also be a part of the perception due to a more V-shaped sound sig.  Upper mids are very similar in quality, while Trio’s lower mids are a bit leaner.  When it comes to quantity, mids are more recessed in Trio, while Indigo mids/vocals are more forward and have more presence.  Both have energetic treble with plenty of sparkle and airiness, but Trio’s tia sounds splashier in comparison to more controlled Indigo treble.

Indigo vs Campfire Audio Solaris 2020 – Also an interesting comparison to another popular hybrid.  Here I found Solaris being just a touch wider in soundstage while both have the same depth/height. Both have a balanced tuning, and as a result have W-shaped sound sig.  But there is some difference in bass impact where even with its deeper sub-bass extension and a good punch, Solaris has less weight and low end presence then Indigo.  In comparison, Indigo bass scales up in quantity to give you more sub-bass rumble and stronger mid-bass punch.  Mids/vocals are similar in quality, being more natural and detailed, though Indigo has a little more body in lower mids while Solaris is a bit leaner.  Both have a clear and sparkly treble, with plenty of energy, but Indigo treble sounds more natural while Solaris treble is a little brighter and a bit less natural.

Indigo vs Mest MKII – to summarize what I have already covered in Sound Analysis section; the sound signature has been changed from mildly U-shaped in MKII to balanced W-shaped in Indigo.  The bass scales up across sub-bass and mid-bass with a little more rumble and impact, not a significant lift, but noticeable enough to add more weight to Indigo bass.  Lower mids now have more body which gives mids/vocals a more natural warmer tonality, and upper mids itself are more forward which contributes to a balanced sound sig change.  While treble in general didn’t change, its perception did due to changes in mids, which now makes treble sound less peaky and more natural.

Source pair up.

In each source pair up I was using a stock premium cable.  Indigo is easy to drive considering its 118dB sensitivity and 13.2ohm impedance.  No hissing was detected.  For your reference, here are my brief pair up notes.  And by brief, I just focus on any changes related to signature and general tonality, without going into too many details of technical performance difference.

Lotoo LPGT – the baseline sound with wide soundstage, balanced W-shaped sound sig; deep extended sub-bass with an elevated mid-bass slam, natural detailed mids/vocals, crisp extended treble.

Cayin N6ii w/R01 – wide soundstage, balanced sound sig; bass has a deeper sub-bass rumble with a similar mid-bass impact, mids/vocals are natural and detailed, treble is a little bit brighter and crisper.  I still consider the sound sig to be W-shaped, but a little extra sub-bass emphasis and treble sparkle makes it borderline mild U-shaped.

Hiby RS6 – wide soundstage, balanced sound with a slightly more mid-forward sound sig; extended sub-bass with a fast mid-bass impact, but overall bass quantity was a bit more neutral; mids are natural and detailed, high in quantity and a little more forward in presentation, and treble is airy, with plenty of sparkle, and overall extra energy.  Probably the brightest treble in comparison to other daps.

iBasso DX300 w/amp11 mkII – wide soundstage expansion, W-shaped balanced sound signature with a deep sub-bass rumble and stronger and faster mid-bass impact, natural organic detailed mids/vocals, and crisp and well-defined extended treble. Excellent pair up synergy.

A&K SP2000 SS – wide soundstage expansion, a balanced W-shaped sound signature with slightly elevated deep and textured sub-bass rumble and a faster mid-bass impact.  Mids were natural, detailed, with a fuller body in lower mids; treble was extended, airy, sparkly, but not as aggressive, more controlled.

Conclusion.

In the conclusion, let me get back to the question I raised in the intro, what is Indigo?  In my opinion, I think it is more than one thing.  From what I have been told, UM made only 200 pairs worldwide and once they are gone, that will be it.  So, it is a Special Limited-Edition release.  Would I consider Indigo as MKIII or next gen Mest?  It definitely has Mest DNA, inside out.  The driver config has been upgraded from 8 (DD/4BA/2EST/dBC) to 10 (DD/4BA/4EST/dBC) and the tuning has been refined to give you more natural tonality with a slight elevation in bass and fuller body more forward mids that change the sound sig perception from mildly U-shaped to balanced W-shaped.

But it is more than just internal driver config change and updated tuning.  The whole shell was upgraded with all new finish carbon fiber material and a new premium 3D Sapphire Pinewood faceplate.  The shape of the shell remained the same, but everything else has changed, including new replaceable nozzle mesh filter and relocation of bass port vent.  Plus, they stepped it up with an all new PWA stock cable that features thicker conductors, matching color deep blue sleeve, and an all-new custom design bronze hardware to match faceplate frame.  Even the included Dignis storage case has been customized to match Indigo color theme.

The price has gone up as well, and I did receive quite a few questions asking me if the difference worth the new price tag.  In my personal opinion, even from reviewer rather than consumer perspective, Indigo has so many inside-out upgrades going from MKII that I find the price increase to be justified.  As a matter of fact, while the new driver config and tuning felt like MKIII upgrade, the exterior redesign along with a new cable and customized Dignis case felt like the infusion from UM flagship Fabled Sound.