Its bass is very good,
but it's flat, like a normal open back planar. Very good quality, but not that much quantity like from a 1266. You would need to EQ it to reach that.
I will post my findings in 1-2 days

.
@Exekuhtor A fewof songs for evaluation, I appreciate they may not be your thing.
Limit to your love - James Blake **Watch your volume!! I MEAN IT!!** - What a crazy silly song. Immanis can really make this sound unbelievably knockout and clean. It doesnt quite hit the lows, off the drum hit, there is a depth of note described by Abyss. If you'd never heard it on Abyss, you'd probably be mighty pleased... I listened to this song over 20 times ... each time, Immanis just got better and what i thought was a kicking by Abyss turned out to be a flavour choice. On Immanis, the first time the bass kicks in, that next 10 seconds describes the changing bass tones stunningly, not the little individual changes but the overall tone of it, and that detail is lost on Abyss.
Star Boy - The Weekend. The underpinning bass is lost on Immanis, it makes the song sound empty. (Blinding lights feels similar) These two clearly show me where Abyss can hit a deeper note, those notes underpin the entire song. I even straightened the AByss to give a fighting chance but the Abyss bass was already a masterclass.
Get Lucky - Daft Punk - The difference is far clearer here. Immanis, where is my bass? Abyss, there it is! Again, it completely underpins the song. I wouldn't even describe this as sub bass and yet its almost absent on Immanis. Im hoping LCD4 can give a good rendition of the above too.
Motherboard - DaftPunk - Loved both headphones here... Bass was not a priority, dynamics were and this is a very exciting dance of electronica on both hedphones. Control and Imaging on Immanis is second to none.
These sorts of songs describe my "Other main listening" where Immanis doesn't quite hit the spot in the bass regions. Its also the kind of music that doesnt need technicalities to impress.
My AB'ing was with Abyss off speaker outs, Immanis on XLR out. Both were fairly close volume wise, i'm finding Immanis is more sensitive than Abyss but the change in ouput power on different outputs brings them fairly close in output volume. I'm close enough to have each headphone changed in 5 seconds.
An interesting aside, I find both immanis and Abyss to have a very similarly wide soundstage and this is one thing i utterly love.
Whilst i was burning in my Immanis, i listened to it exclusively for the full week before going back to Abyss. Abyss tonally is really bad for some instruments! Immanis is a spoiler there. But, it still a very fast and incredibly impressive headphone for certain genres. I still hugely enjoy it - which is annoying as i need the LCD4 to take its place!
One last comment, how do 80 year old tubes allow an valve amp to be so incredibly fast, detailed, holographic, bassy, intense, etc etc ... It absolutely blows my mind.