Lose the arcs around the mic. Make the color of the "voice" a lighter gray. Change the color of "VOICE" in the slogan to the same blue in the rest of the logo. After you make those changes, let me see the logo on white just as you currently have it and then put it on black with the same changes made for the white background. In other word, you should be able to take the logo off the white background and put it on a black background without losing anything due to the color of the letters.
For 31 & 32, lighten the gray in the slogan just a bit so it shows up a little more on the black background. Also, let me see the slogan in red, perhaps a gradient. So, if you don't mind, I'd like four new ones: two with the light gray slogan on both backgrounds and two with the red slogan on both backgrounds.
I actually have one more suggestion. How about making the mic a gradient gray/silver, but just the mic. Leave the "U" blue, but change the crossbar transparent so it take on the color of the background..