I`m bumping this old thread because I`m right in the middle of it now and don`t want to start a new one yet. Let`s see how this works, if there happens to be any fifts-tuning players checking TB out.
I got into fifths thing quite recently and bought some Pirastro flat chromesteels with low B, solo Fis, D and solo A. D and A are decent but the lower strings did not work at all. I was all too impatient and ended up using Spiro mittel A downtuned and D with FCS B and solo A ( or I used them every other day, while getting crazy about wether making the switch or not, the other days I was using full Spiro mittel set in fourths

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I finally got the full Spiro Red Mitchell set today. I have to take my bass to the luthier to check out what needs to be done setup-vice and I know that the strings are completely new. The low C is wonderful, it roars like crazy, the G is marvellous too. Then there`s the typical Spiro mittel D and a high A that is on the thinner side a little. I like how the set sounds, it seems to like a little less tension than the fourths mittel set, or at least for that low C. I took the strings down a little, now set up at C 8mm to A 5mm.
On my bass this makes the higher strings sound louder than the low C and when I raise the action the C starts to make quirky sounds and gets harder to play. Again, I know that the strings are completely new and it will take weeks to get them settled in properly.
I will try the FCS D and A tomorrow, even when they are significantly thinner gauge than Spiros. I kinda got to like the older school-ish pizzicato sound of that A string.
The bass will go to luthier and the strings will be played in, but meanwhile I`d like to know what strings are you fifth tuning folks using with Spiro C and G?
Dominants are popular and I would like to try them some day, but if the acoustic volume of the C string maintains to be an issue I`d be interested in something not so loud, to balance the difference. I practice 50 / 50 arco / pizz but play exclusively pizz with other people.
Thanks in advance, Reiska