best strings for a slide on a short scale bass?

Are you talking about having upgraded your bass from 2-string to 4-string? What exact make and model of bass do you have?

 

I'd go with a short scale set of D'Addario Chromes for a bright sounding flat.

 

Or a set of half-rounds, such as GHS Brite Flats.

Products - BASS BRITE FLATS™ - GHS Strings

They're brighter than typical flatwounds but with a smooth surface to slide on.

 

What sound are you after?

I bought a cheap SX short scale jazz copy just to make a slide bass a la Mark Sandman of Morphine. Goofed around with some strings and I ended up settling on D’Addario flat wound guitar strings in heavy gauges. They have less mass than bass strings, play real nice with the slide and sound huge.

Roundwounds on slide bass rattle too much IME.

 

So there was a lot of trial and error to get to where I am now. First issue I had to deal with was the slide clanking against the neck especially in the lower positions. I did some research (i.e. looked at pictures on Google) and realized that Sandman used a raised nut of the kind slide blues players use. So I replaced the stock nut with a stupidly high nut make out of a piece of hardwood. Like this:
This solved the problem of constantly hitting the fretboard with the slide, and it also gave me more room to play with the dynamics. (The nut is pretty janky but it works so I'm leaving it until it breaks.)

I went through a bunch of bass strings first. Roundwounds were ridiculous with a slide, way too much chatter. Bass flats were good but they never rang out the way Sandman's strings did, they always ended up sounding like short scale flats - lots of oomph and thud but none of the harmonic richness. (I tried Chromes, Labella, Rotos... I spent $$ so you don't have to). I got hip to flat wound guitar strings from someone on here actually. They pointed out that Sandman approached his instrument less like a conventional bass guitar and more like a slide guitar in a low register.

I looked over D'Addario's tension charts before taking the plunge and it seemed using the guitar strings doesn't put any additional stress on the neck. If anything, because you are using two fewer strings you have lower tension overall. The truss rod is somewhat irrelevant in this set up because even if the neck is bowed it doesn't affect the playability.

My slide bass is tuned to D and A using D'Addario flat wound guitar strings, CG075 and CG056. They were a touch bright at first but after a couple of gigs they settled in. I haven't replaced them in a couple of years. They sound balanced relative to each other to my ears.

Let me know if you have any more questions. I love slide bass and there isn't a lot of solid info out there so I'm happy to share my experience.

And I don't think anyone will ever play it like Sandman.

 

Tapewounds probably won’t work out

 

Try shoving some foam under the strings at the bridge. Might help with that open E sound.

 

Also, what kind of slide are you using? Metal slides are much more brash than glass. I use the Dunlop tempered pyrex slides - they get a pretty warm tone relatively speaking.

 

I've been playing slide bass for upwards of 40 years. Ideally, I recommend a fretless strung with GHS Pressurewounds or SIT Silencers. Until recently I used a Travis Bean fretless, which was really fab for this application. But after 4 decades the weight finally got to me and I had my luthier friend build Marco Cortes me something new and wind me pickups specifically to enhance slide playing. Early results are very promising, so I'm currently working out a custom onboard electronics package for it. I realized that this is way beyond the scope of what you're asking for, but that's all I've got.

Here's my slide, made of very soft brass for me by a friend ca. 1978:




The indentation to the left catches the webbing next to my fingers (either side of middle finger), the ones on the right facilitate gripping it. All those surfaces are useful for aggressive scraping noises as well.

 

Charlie, do you reckon the Ernie Ball (cobalt) Slinky Flatwounds might also be a good choice? IIRC you use those on your amazing-sounding, Q-Tuner pickupped fretless, so you may not have a direct comparison at hand.
I haven't tried the EB cobalt flats myself yet, but they regularly get mentioned as being the brightest of the flat bunch (perhaps except for those players whose body chemistry happens to kill them faster than Chromes), if we restrict to flats proper, so I thought they were worth a mention, in case @H-S absolutely needs to have a low E (if you don't, I second @ihixulu's recommendation of D'Addario guitar Chromes, which can be had up to 80 gauge).
They only come in long-scale, and using a low E may expose it to breakage on the Mustang. Speaking of which,

does the bass have the sole string-through-body loading option, as the originals did? If it does, stringing the E and A strings in the former A and G positions, instead of E and D as you currently have them, might be all that's needed: the E would then have its tuner farther from the nut, hopefully right when it tapers.

Anyway, single Slinky Flatwounds can be found here:
Ernie Ball Cobalt Flatwound Single Electric Bass Strings from Fret Nation

 

I've only used the Cobalt Flats on my Crescent Moon fretless with the Q-Tuners. Before that it sported T-I Jazz Flats for many years. That bass has really low action and I never have used it for slide much at all. But still, the Cobalt Flats are pretty bright and would probably sound fine. OTOH, they have a reputation for being pretty fragile, and the way I use a slide might easily tweak the windings, I think. I use the slide in my right hand, like a bow, a substantial amount of the time. And for that to work well, I need some texture on the string to create enough friction. So I actually tend to prefer roundwounds, and then reality kicks in and the halfwound/groundwound/pressurewound spectrum ends up bringing the best trade off set for my needs.

The Crescent Moon bass just always felt a little too uptown to abuse the way I often treated the Travis Bean. So when I sold the Bean I had it in the back of my mind to get a beater bass so I wouldn't have to worry about it looking all Willie Nelson from slide damage. But when my friend told me he really wanted to build me a daily driver fretless I couldn't resist spec'ing something that would bring some new things to my slide repertoire. He makes killer relic'ed Jazz Bass variants and that would have been so easy...but no! I was like: "let's use some of those NOS parts that have been collecting dust in your shop for years." We settled on a discontinued model, and eventually found the only neck with an unlined non-maple board in the shop. It already was matched up to a body, which had a finish that is way out of my usual wheelhouse. And then he decided to go all rogue on the pickups after playing my Crescent Moon. So this is what I ended up with:



My beater bass ended up having an epoxy infused purpleheart board and neo sidewinder pickups...go figure!

 

The Ernie Ball Slinky (cobalt) flatwounds were introduced in early 2015; if you had them for more than 4 years o'calendar they must have been regular (non-cobalt) EB flats, or non-EB ones.

Got it.

Toploading only, eh? In that case, you either need a) a short-scale (proper=32.5" full winding, tops) low E; b) a medium-scale (34" winding) low E installed in A-string position; or c) a string that's not larger than ~.08", so that it won't risk breakage even though wound full-thickness on the post.*

Thing is, they only make them up to .08":
D'Addario Chromes Flatwound Electric Guitar String .080
Now, there are folks who use typical A string gauges for their low E. I say try it. It's cheap enough, as experiments go. If you use a pick,** and since you're not gonna do any fretting, you may well not find it overly floppy at all.
If the experiment intrigues you, also get a 65 for your A string:
D'Addario Chromes Flatwound Electric Guitar String .065
Next gauge down is a 56, which may be too light, but then again it may not:
D'Addario Chromes Flatwound Electric Guitar String .056


* [If you wax creative, I guess there is a d) option after all: you could use a long-scale E string and wind it on the unused G string tuning post, with the also-unused A string post employed as a pivot (better with something like a wide washer around it or a...something projecting from the slot, so that the E string doesn't touch either the D post nor the A string wound on it)... This jury-riggage would allow the long-scale E string to taper correctly before reaching the tuner. Of course the E string would be wound backwards on the G post, and you'd have to turn the latter's tuning key accordingly.]
* [I'm not much of a picker, but I'd guess one yanks them less with one than with heavy fingerstyle plucking. Well, unless the picking is good n' heavy...]

 

I find that slides need hard on hard contact- tapes are softer and I imagine you’d get a weird muted sound out of it but I could be wrong.

 

Of the regular bass flats I liked the playability of the Rotos the most as they flopped around the least and gave me a good solid surface against which to move the slide. Pretty bright too, but lower output. They are very high tension though so if you are concerned about your neck stability, use Chromes.

FWIW, the guitar flats aren't floppy at all, which surprised me when I first put them on. They have as much low end as the bass flats did, with just more fullness through the mids and up. YMMV, obviously. Good luck with your journey!

 

Best of luck, and have fun.

Most of what I shoot for is kind of a Derek Trucks or pedal steel thing. The new bass seems to kind of want to channel ZZ Top though, so I'll probably take a stab at building some distortion widgets to run with that. But sometimes an old truck full of sheet metal can be kind of cool in its own way too: