The brand and type of strings you put on your bass make a HUGE difference to the sound. In fact, it strings can make as much or more difference to the tone of a bass as the brand and model of the bass itself. Some of the differences between various types of strings include:
Roundwound vs Flatwound
All bass strings consist of a long straight
"core" wire, around which another wire is wound. If
the wound wire is round, it is called roundwound. If
the wound wire is a flat ribbon, it is called
flatwound. Roundwounds are brighter have have more
harmonics, and are generally better for rock, pop, and
country. Flatwounds are smooth and silky to the touch,
but they are much duller sounding, and are generally used
for jazz. They are excellent for fretless basses
because they make the bass guitar sound a bit more like a
standup bass, and they don't wear grooves into the
fingerboard.
Round Core vs Hex Core
The long straight center "core" wire can either
be round, or hex shaped:
The type of metal that the wound outside wire is
made of makes a significant difference. Steel is very
bright sounding but it has a big disadvantage: steel strings
wear down the frets quickly. Nickel has a smoother
sound and doesn’t wear out your frets as fast. So I
recommend nickel wound strings for students.
Coated vs Uncoated
Uncoated bass strings generally last a year or
so before they start sounding dull. This dulling of
sound is caused by oxidization and by oil, sweat, and grime
from your hands getting into the windings and in the tiny
space between the windings and the core wire. Coated
strings have a nano polymer coating that helps the
strings last longer because they help prevent contaminants
from seeping through. I generally recommend coated
strings for acoustic guitars, but not for electric guitars
and basses. They just cut too much brightness from the
sound.
Gauge
Heavy gauge strings sound fat but are a bit
tough to play. Light gauge strings (.040-.095) are
easy on the fingers but a little wimpy sounding. I
generally recommend medium gauge strings (.045-.105), which
is the gauge that comes stock on most electric basses.
They sound good and are not too hard on the fingers.
The G string is .045, D is .065, A is .085, and E is .105.
Recommended Strings
Out of all the strings I have tried thus far, my
favorite for general use are the DR Sunbeams Nickel Plated
Medium 45-105 (NMR-45) bass strings. They are
roundwound, round core, nickel, uncoated, medium gauge, and
they sound great! And they are very reasonably
priced! These are the strings that I am using on two
of my three performance basses, and they are the strings I
recommend for most students to start on. For fretless
basses, my favorite strings are the d'Addario XL Chromes
45-100 (ECB81).