My experience so far has been that using a 6th string for the basses from 7 - 11 is OK but:
1. I find you do need to ensure that the string height at both the nut and saddle is reasonable otherwise some buzzing can occur and the feel is a little "soft"
2. using the smaller diam strings results in a somewhat subdued bass sound. This may be desirable if your trebles are more mellow or you dont want too much Campanella or resonance effect.
3. for a full sound I use the following on the Milagro / Bartolex 11 string Alto's I sell. It gives a full sonourous bass with strong resonance and Campanella effect. (of course this may not suit your playing or desires but thats up to you)
Strings 7 - 10 are nominal 1.27mm diam
- Hannabach Silver Special C-8 (8158_MT) or Savarez D-7 (5207R) or La Bella C ( NYL028W 0.052) or Aranjuez C-7 (concert silver 7-C)
11 is nominal diam 1.44mm
and use B-9 (8159_MT) or Savarez C-8 (5208R) or La Bella A (NYL030W .056)
4. my personal preference which suits how I play or want to sound is:
- Aranjuez C-7 (concert silver 7-C) - the gold colour is useful as a visual ref marker at 7.
PS I am also working on a possible technique to slightly colour normal silver strings - I will let the forum know if I am successful.
Strings 8 - 10
- Hannabach Silver Special C-8 (8158_MT) or Savarez D-7 (5207R)
- Hannabach Silver Special B-9 (8159_MT) or Savarez C-8
Most bass strings are pretty much similar in sound quality between makes but of course definately not so on the top 3 treble strings. So really any of the above well known brands will be good. The Aranjuez seems to get duller quicker so its life is not as long I find. (also possible that the 7th string tends to be used slightly more than the other basses and occasionally fretted as well - so maybe this affects its life ??) The bass strings 7 - 11 last a long time compared to the 1st 6. Usually the 4th needs replacing long before any of the others then 5 and then the trebles 1, 2, 3 in my experience.
I suppose the only other suggestion is to make sure that the 1st 5 strings intonation is checked right up the fingerboard to Fret 10 at least and proper set-up adjustments to string height / nut / saddle or all are done to get it reasonable. (You will never get it perfect but should be able to maintain a +/- 3 - 7 cent variability from fret 0 - fret 14. I say this because with the shorter strings and higher pitch, intonation irregularities occur more easily and tuning is more sensitive than a 6 string.
I hope my ramblings are of some help. String choice often comes down to a personal level and I urge you to experiment as many of us have done using suggestions as a guide. Strings By Mail I can highly recomend and they sell strings individually with great friendly service and good prices. Good luck with your project and playing.
Kind Regards from a very wet Sydney in Australia. Peter Mony www.laudarra.com.au