I think it's a mish-mash, actually, and not one exact font.
The lower-case letters, especially the "e", point to some flavor of Avant Garde. But the upper-case letters look more like Helvetica/Helvetica Neue. And the round dot on the lower-case "i" is not from either of those faces. It's more like Futura, though the balance is completely different. I'd say the designer just took the square dot off the Avant Garde "i" and put a round one on.
Yes, it's completely kosher to mix fonts for something like that. There's also a bit of hand-editing of some of the letterforms. The u/c G, for instance, has a squared block foot. The normal Helvetica G has a slight taper to it.
The "ThreeSpeech.com" is definitely a flavor of Helvetica/Helvetica Neue, though.