Thanks for the answer.
Unfortunately I can't afford the A6.
I don't doubt they are very good, but > 3x price for the same structure I can't justify.
Am curious to play with the filters though.
I Have both A6 mini and Spring 1, they are great IEM but i can say they are side grade to each other, with their own pros and cons.
Bass is a definite win on A6 mini which utilizing same driver like the big A6, tight, fast, clean and smooth, very well presented with great tuning proportion between sub bass and mid bass. Best bass you can fin in this price range along with NX7 / Pro bass. Spring 1 biggest weakness is on their bass. They have speed, that surprised me as using 13mm DD, tight, fast decay but they more sub bass focused that made depth extension shadowed by hump on mid-upper bass, around that 80-100hz. If they tuned to be more sub bass focused, there could be a different story.
Mids is on difference presentation, the A6 mini with black filter, have a bit distanced vocals presentation that perceive depth on soundstage, create a virtual stage, while vocal on Spring 1 is intimate with much details, and more balance between lower and higher mids vocals. For mids i prefer the Spring 1 mids, they are detail and smooth, thinking of Spring 1 made me straight away remember how delicate their mids are. A6 mini with red filters are muffling / veiling the mids details, but they are become more balance between male and female vocals, but i can hear veiled mids if using red filters. A6 mini mids are crippled, as I can think thats why big A6 are having 4 more BAs covering mids. Meanwhile, the Spring 1 mids is very very great.
Highs. No matter what filter are you using on A6 mini, they wont filter the high portion much. To me, the filter is really affected high mids, especially 2-4khz range. The piezo on A6 mini handles highs nicely, details and smooth and airy, but in fact is a bit smoothen out that i can crave a little bit more energetic trebles, just a little bit. Treble is safe on A6. On other side, highs on Spring 1 is presented similarly smooth, but they have boosted on 8khz, so high that can made a smooth soft tizzyness, its not harsh or disturbing or fatiguing just they are there on 8khz, sounded not so natural but in the same time give you more sparkles there.
Timbre is a little bit better on A6mini, they more correct, spring 1 out of the box need grill mods to be sounded more natural
Soundstage is wideee on both, but the A6 mini sounded more natural, imaging also similar level. differences are subtle here
so to sum up, Spring 1 mids are really hard to beat on this price range, but A6mini have other pros, especially bass that outperform Spring 1. THey have their own cons, Spring 1 is great with their mids, but have weakness on bass. The A6mini is great on bass and soundstage, but their mids are imbalance between lower mids and high mids.
But don't let these downside bugging you, most of IEMs cant please us, they always have cons, especially on budget level. THere are only few IEMs that i fell dont have major flaws but sometimes they dont have "special ability" or strength section. With the more you going up on upper tier, the less you find weaknesses but you have price to pay of course, you pay hundred dollars for a little bit improvement and refinement. Its a diminishing return hobby at first place.
But on sale price like this, A6mini is a great snatch, but dont expect an upgrade to your Spring 1.