If your pianos old bass strings sound dull and "tubby", there are
various ways in which you can rejuvenate them.  The key thing is that
you must remove as much as possible of the dust which collects between
the windings and the core of the string.

The easiest way to do this is first to make a "knot" in the string by
looping it around once and passing the end through the loop.  If you
then roll this loop up and down the length of the string, so to speak,
tapping the string as you go, this will cause the windings to
alternately open and contract, allowing the dirt and dust to fall out.
In my experience, this can make a dramatic difference to the tone of
a string.

A further refinement is to boil the string in a pan of vinegar, in
conjunction with the above operation.  This removes even more dirt and
visibly cleans the string.  However, if you try this, please don't
make the same mistake that my father did by performing this operation
indoors -- every piece of brass, copper and silver in the house turned
black, and my poor Mother was beside herself! The strings on our Weber
duo-art grand looked and sounded fantastic, however.

Without wishing to deprive piano string manufacturers of much-needed
work, it is surely better to rejuvenate rather than replace bass
strings where the original strings (a) remain in situ, (b) were
probably of better quality, in a top-grade instrument, than modern
generic replacements could possibly be and (c) will give a more
authentic sound than replacements.

Best wishes to all.
Rowland Lee
Lincolnshire, U.K.