I can help with that! I addition to all of the nylon / low tension strings I’ve used I also have spent a bunch of time on Superflexible solo (still like these on my EUB.) My take is -
1- They are much thinner and slightly tighter than the nylon strings I’ve used, and I would set the string height a little lower. I would still say they are very slappable compared to, say, Spiro Weich.
2- Pizz and slap sound has more sustain, by and large. When fresh they can be a little twangy, but when they die down it’s a good warm sound IMO. If you need to both Slap and get more of a modern jazz sound out of the same bass these can be a good option. An orchestral-designed string like Jagar Dolce would be a good option if you want a string that both thuddy and all-steel, but they might make acoustic jazz pizz playing a bear.
3- Because the strings are teeny and at orchestral tuning they aren’t at their “optional” tension the acoustic output was compromised on my basses. This was my main complaint with them on an acoustic double bass.
4- They sound really nice through a magnetic pickup. The SF solos are the best set I’ve tried with my Krivo (which I sort of endorse, full disclosure.) After the initial break in they are very warm sounding.
5- I also spent a bunch of time on 4/4 Spiro solo, but the results were mixed. The high string (solo A tuned to G) on the 4/4 spirocore solo set has sounded weak and sonically unbalanced on every bass/pickup I’ve used it on.
I will say I found an oddball mixed set I liked a lot- 4/4 Spiro Solo F# + B (tuned E + A) with a Eurosonic White light D and Medium G. This was a set with even tension (helpful if you go for a flatter slap-specific bridge shape) and really nice gauge match in the traditional set of gut kind of way. The E and D are the more or less the same gauge, as are A and G, which has been the case for the wound bottoms, plain gut top sets I’ve used. The Euros seemed to match the spiros well in timbre and didn’t sound to bright/twangy, without a noticeable break in tone between the A and D. This worked well with a magnetic pickup and had good acoustic output (meatier sound than a full set of SF solos played sans-amp.) Perhaps this set was a little brighter through the Krivo, but it’s been a while. If I needed to play loud-as-hell rockabilly and unamplified Bluegrass/Trad Jazz on the same bass I would still use this combo. Here’s a picture of this weird set. Pretty slick, eh?
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