I can give you some very preliminary (and not entirely accurate since Tia Forte isn't burnt in) comparisons: (done with Chord Mojo, Jriver MC21 bitperfect and SPL meter for volume matching)
A18w/M15 vs Tia Forte...
Ray Charles - Genius Loves Company 24/192 (this is the most well recorded song I've ever heard in my life and I've heard a lot of audiophile recordings on competent setups, it is a good mix of male and female vocals with everything else being exceptional as well):
A18 w/M15: More analytical, less umph in the lower mids than Tia Forte. Male and female vocals sound balanced with regard to presence and both are slightly more forward than Forte. Images have very very slightly more texture (maybe 1-2%), but also have the good solidity of Forte as well.
Tia Forte: Lower mids have a vibratory feel to them, more body and weight than A18. I would have expected Forte to have less resolution but it's holding it's own vs A18 in detail reproduction; it's just a different presentation, maybe 1-2% difference on high definition resolution/textures-Forte can hang with A18 in detail. Male vocals sound a tiny bit more forward than female vocals on Forte. Images have more solidity on Forte, more weight; the little guitar fiddling at the end of the song causes what feels like tactile/vibratory bass on the Forte whereas on A18 it's less impactful.
Lenny White - Stank (Binaural) 24/176
A18 w/M15: A18 has more sub bass umph and power with the super deep drums played at 4:08. Both are exceptional with regard to sound stage imaging, layering and separation.
Tia Forte: Seems to have more space between the sounds at the very edges of the stage, for example there is a set of hand drums played at about the 1:25 mark where the drums are configured such that they are attached sideways to each other, but in reference to the microphone they are like this: (M is microphone)
.............................................. D1
.............................................. D2
......................M.....................D3
.............................................. D4
...............................................D5
The Forte makes it more noticeable that they are in series vertically(there's slightly more stage height/vertical space between D1 and D2, etc) , the A18 reproduces this stage height and positioning effect as well it just jumps out at you less. It's more obvious with Forte. Forte has less umph with the super deep drums at 4:08 and that less umph allows more reverb to shine through-the deep drum is also less impactful than with A18.
Mark Nauseef - Gears 16/44 (drum test):
A18 w/M15: A18 goes deeper in tone with regard to sub bass, more weight in the lowest frequencies. The cymbals (I think) at the 4:00 mark have less sparkle on A18, they are more centered in the mids and upper mids.
Tia Forte: Forte has less tactile/impactful sub bass, favoring detail in decay instead of umph. More of the sparkle of the cymbals (or maybe triangle?) at 4:00 mark comes through with Forte, this instrument is more centered in upper mids and highs with Forte.
Lindsey Webster - Back To Your Heart 16/44:
A18 w/M15: Bass is more visceral, fatter and hits harder with A18.
Tia Forte: Her voice goes slightly higher with the Forte.
Agalloch - In the Shadow Of Our Pale Companion 24/192
A18 w/M15: there is a very faint low volume growl almost Buddhist monk sounding at about the 7:00mark, with A18 there is more other stuff happening around the sonic image making it's image solidity and audibility less.
Forte: Easier to pickup this low growl, more clarity around the sonic image and more image solidity to the growl.
General Observations:
+ People were saying Forte has more bass, I'd say it has a slight mid bass bump but overall and especially in sub bass A18 punches, slams and rumbles harder
this could be because of the custom fit of the A18 although I did a seal test with Forte and it passed. I will be able to look into this more tomorrow when I've heard U18.
+ I haven't listened to U18 yet, it's burning in.
+ The 64 audio premium cable is totally transparent, doesn't color the sound in any way, seems to allow the monitor to show it's natural tuning, a good reference point.
+ Both are exceptional monitors with transparency, naturalness, imaging, layering and separation that beat anything I've heard before, likely the Tia driver is responsible for this.
+ Mojo sounds incredible with these new 64 Audio IEMs, imagine Hugo 2....
+ A18 is thicker in the sub bass areas, Tia forte is thicker in the mid bass.
+ These observations are totally preliminary and subject to change after burn in with Forte.
+ Having heard Forte...I like it and it is spectacular but since I own and love A18 I feel like it has everything I need as well and I am tempted by Forte but also simultaneously content with A18-it has a more visceral low end.
+ Tia Forte is also very fast sounding like A18, it can keep up just fine-it is BIG and dynamic but NOT sluggish
+ What
@Barra said about wanting to jump on the table and air guitar with Forte is 100% true it's similar to the best tube amp you've ever heard: massive, weighty, dynamic. There's something behind the sound, something vibratory and it's acting like an amplifier, very hard to describe.
+ They both sound quite similar in many ways and possess the same technical capabilities which are without a doubt TOTL in every category.
Keep an eye out for my forthcoming reviews of U18 and Tia Forte. It'll be probably 3 weeks. 1 week to listen and write down all the notes I can, another week to compile and write the review, another week to put it all together with photos and formatting.
