Dead Low B fix?
 

Maybe this should be in "Strings", but it is applicable to the dead B syndrome on some basses. On my Fender P5 I've never been happy with the low B string. The notes below E seemed to be dead thuds and notes above that are okay, but nothing great. Last night I was messing around with it and I noticed that B string wasn't really straight across the saddle, it seemed to hump upwards. So I pressed on the B string at the bridge to make sure it has the propper witness point and it had a very noticeable improvement to the B string. I think it's less of an issue with other strings because they have more tension and will fall into place better. So if you're trying out a bass at a store and it seems to have a dead B string, just give it firm press at the saddle, tune it and see if that helps.

That's why I love tapered strings :)

I use Fender 90505-M flatwounds on my Precision 5. The B string has a tapered end which causes it to sit nicely in the bridge. Sounds great.

TD

I use the Carvin roundwounds made by LaBella here. The B in this set is also tapered, and is balanced pretty well to the tone and volume of the other 4 strings.

Chuck

I put Sadowsky flats on my P5. They have a tapered B and sound great.
You should always set your "witness points" on all the strings at the saddle and the nut.
One more thing I found on my P5 was the nut slot on the B and E strings needed more taper towards the tuning post for a better break angle.

Check out Rodger Sadowsky's video "Behind the notes" on youtube.
He gives some great advice about setting up a bass.
That man knows how to make a 34" 5 string play and sound good.

Frudua (Italian bass maker) has a video on enhancing the B string sound.
http://www.youtube.com/watch?v=kaKeGwZSIYA

OP, glad to hear it was a simple fix. Some basses have poor B strings no matter what you do.