As an audiophile who followed the audio industry very passionately in the last decade or so.
I personally consider the sp5 to be my end game closed back headphone, I won't look for any other closed back, and that's coming from someone who never believed in end game headphones.
The only negatives are first the weird impedance which makes the headphones get affected by which device, amp, or dac it's connected to, they might sound noisy or you feel something is off, that's because they don't mask those things.
It shows you the quality and the characteristics of your components much like the focal utopia and Stellia.
The other thing is it's on the bright side.
Now to the real talk.
This headphone sound amazing the details that comes out of these make nearly all totl cans ( except the equally fantastic Stellia )sound like beats, and beats sound like toys.
The sheer amount of details the monitoring room like sound stage and insane imaging just makes these a treat.
They handle everything effortlessly they make my RME adi dac seem like it's not trying or challenging these headphones in any way.
The bass isn't LCD 2 quantity but infinitely better in quality they make the LCD 2 sound like Sony xb headphones.
The bass is on the same level as my Stellia and just a hair from being stax like.
The mids are magical nothing is added just clear voice clean, insanely detailed to the point of absurdity and maintain a certain speaker like feel, focal utopia came to my mind here.
The treble is elevated but level and not in spikes that's why it's never painful unless the track's quality is poor.
It shows you everything and I mean everything microphones errors or quality issues everything even if some dropped something, and it extends all the way to the stars.
The end.

This is a very polarizing set of headphones, as seen in reviews here, and on YT.

Just to level set - I want the reader of this review to know that I'm very a much a fan of Adam products. I started with a set of T7V monitors, graduated to A7X monitors, and now have their flagship 2 way - the S2V. My goal in getting new headphones was to be able to test mixes from those monitors and see if they translate on headphones. I also always like to check low end on cans vs my monitors.

Straight out of the box, there are a couple of issues with these. There's a little bit of a hump around 100hz, Not sure if Adam wanted to sweeten up the bass, but it does introduces some 'boxiness' to the sound. Past there, they are relatively flat, but then things get out of control from 3khz to 12khz. Around 3 kHz, there's a divebombing null, then this null turns to resonances around 5-7 khz. This sounds like a weird comb filtering and the listener may interpret this as 'airiness' but it is 100% not true to form. To be perfectly honest, none of my Adam monitors exhibit this at all, which is very disappointing.

Fortunately, this can be remedied with EQ correction software. Luckily, Sonarworks has just added an SP-5 preset which fixes the null at 10 hz and the wacky comb filtering from 3-10 khz. Once they are flattened out, the sound is downright boring, but that is what you WANT when trying to suss out problems in the mix.

Overall review is that these are good cans with great soundstage and minimal phase issues, but do not buy these for 'pleasurable' music listening, or you will be very disappointed.

wollez !