rsautrey, one of our resident string experts, is correct from what I've read, according to the Ox's latest string preference. If you want classic Entwistle "PANG!!!" get a good P-bass pup and some Rotosound Swing 66's.
Yeah, rickbass1 is right. For what most people consider his "classic" tone, Rotosound Swing Bass 66 was the string. He supposedly was instrumental in the development of these strings too (stainless steel roundwounds). The Maxima Gold strings are very expensive but "supposedly" have a nickel feel with a stainless steel sound. Do a search of "Maxima". There have been a couple of other threads about these strings. Hope this helps!
im not sure about the strings ( i use dr sunbeams)but i started using a tech21 bass compactor into my sansamp and i can dial in the ox"s sound. ive had people come up to me at gigs and say it sounds just like the ox's sound( not the playing,)just the sound