In July I added a used pair of Stax SR L700 stats to my collection, bought from a fellow head fi'er. Again - based on using one headphone exclusively each day - I came to the following conclusion. I felt the Stax were superior technically, but because of a more pleasant tonality - I liked the Kaldas RR1 just as much. Which on it's own, is amazing to say - since the Stax retail for $1500 new, and the Kaldas start at $500 new. That said, I realized after a direct head to head comparison - my first impression was wrong.
I did the same thing - shuffled through my collection for about 3 hours yesterday, swapping when a different type of music came up - or if I was really impressed with one or the other headphone. Since both were connected to my Stax SRM 717 at the same time, swaps were quick - I'd only have to adjust for volume. The Kaldas RR1 are much harder to drive at a decent volume. I used the internal switch on the SRM 717 to set it as a power amp, no volume control - and the preamp on my DAC needed to be at 29 out of 40 for the RR1. Comparatively, the volume needed to drive the Stax was 24 out of 40.
Treble - No contest. The Kaldas RR1 rolls off pleasantly. It's a much darker presentation. The Stax extends as far as my 42 year old ears can hear - and unlike my old L300 it's not peaky or shouty. I thought I would prefer the darker presentation of the Kaldas RR1. But switching on certain songs from First Aid Kit, Loreena McKennit, or the random classical track - it became clear that the music came alive with the Stax. The highs on those songs really needed the air the L700 provided. The music was exciting without being fatiguing. On a complex track like "Sweetness Follows" by REM, the mesmerizing bass of the RR1 makes the song sound 9 out of 10 exciting, but the L700 treble balance adds that last bit of excitement that puts them over the top.
Mids - Close, but the Stax L700 wins on detail by the smallest amount. The Kaldas RR1 soundstage is more intimate, but I pick up the slightest bit of more microdetail on voices with the Stax. On tracks with a lot of bass, the mids can take a small step back on the Kaldas RR1 by comparison. I found this on the random track "Even Though" by Sugar Ray.
Bass - Kaldas wins on quantity, Stax wins on layering and detail. I can make out individual percussion instruments better. I have not performed the blu tack mod on my Stax. I've never felt that I needed more bass than the L700's currently provide.
Soundstage - Kaldas RR1 is more intimate, L700 is larger, but not huge. I feel neither is subjectively better - for me it's a personal preference depending on how I'm feeling.
Comfort - My Frankenstein Kaldas RR1 win. If I have a complaint - it's the plastic assembly of the L700 housing, which like my L300's creaks when I move too much. I also have problems getting a good seal behind my ears with the L700. Where the seal from the RR1 Vesper pads is top notch.
Overall - comparitively, the RR1 is a much darker headphone. By comparison it's mellower and easier to listen to for long periods of time. But if you don't find it distracting, the L700 is more neutrally exciting, providing all the detail that you might not need. I was surprised to find out that I enjoy the L700 more than the RR1 after a head to head listen, which is not a knock on the RR1. The only songs I found where I definitely preferred the RR1 were overly complex tracks from Led Zeppelin where the cymbals and high frequency energy could be confusing or distracting.
For the Kaldas, I'd seen one bad video review from Max Settings which gets quoted on Reddit. I think most of his complaints, like channel imbalance might have been due to the manufacturing issues found in the early models. I wouldn't be surprised if the Kaldas RR1's he was sent had frayed internal wiring. I believe the review would have been quite different if he were sent one of the current versions.
While I was surprised to find that I enjoyed the L700 more than the RR1 - I really shouldn't be. The price difference is 3X. I still think the Conquest is an outstanding value at it's price. I've often read (I can't judge the accuracy) the Kaldas RR1 described as a mini Stax SR007, and the L700 as a mini Stax SR009. If true, I'd love to see a Kaldas RR2 tuned more like the SR009.