There is usually a red mark on the Beyer drivers I have worked with but I do not see it in your photo. The way I have hooked them up in the past is red to positive, then I check for the other connection using an ohmmeter. While impedance and resistance are not the same thing, if you have a 32 ohm impedance etc. it will read fairly close to that on an ohmmeter, that tells you that you have the proper two connections. On photos I have seen the red dot is to the left of the solder pads so I would figure the hot being there and the opposite side being ground. If those drivers are 80 ohm, then that is what you should read across the proper two solder points. Another way to tell would be to place a signal across two points and check for sound, the headphone output of a phone or high res player for instance with the end of a wire stripped so you could get left or right channel and ground. Personally I run two separate inputs to those drivers but originally they may have been a one cable set up. If you are trying to do that, let me know and I will try to help you further. You will in a sense be making a DIY cable to each driver so personally I do not think this question is out of place. There are three connections on such drivers but only two are needed per side.
Tom