kf2qd:
"+" and "-" on a speaker are there for phasing purposes. On a speaker this small it wouldn't really make much difference, but on large speakers where they are not phased properly makes for a big loss in bass.A way to test the the result of phasing is to take and drive 2 speakers, side by side, from the same source and reverse the phasing on one and listen for the difference in the quality of the sound. One effect from 2 speakers that are closely spaced but different in phase is that the sound will be quieter at a distance as when on speaker is pushing air, the other is pulling and thus they will tend to cancel out.
Another means of testing for proper phasing on loudspeaker is to simply wire a 1.5vdc battery to the speaker terminals and note if the cone moves out or in. At my age I never trust my ears alone to make these kind of connections.
Spent a decade or so in the late 90s early 00s collecting quality vintage solid state hi-fi equipment made in the 70s (Marantz, Kenwood, Sansui, etc) from thrift stores as people were giving away their quality stuff for the cheap plastic 5 channel stuff. Sold lots of the stuff on E-bay for pretty big bucks and keep some of the better stuff for myself. Fun hobby until the whole world seemed to learn about the golden age of hi-fi equipment and the thrift store finds dried up. 
Lefty