The Alex Voice Feature Very Fast

I'm on an iPhone 6 Plus and was looking around in settings today. I saw the feature of Speak Selection (where it reads text that is highlighted) under Accessibility. I thought this was pretty cool so I turned it on. There are several voices, on of which is Alex, "a high quality U.S. English voice that delivers natural sounding speech". After I downloaded this and tried it out, Alex spoke much faster than any other voice. Is this how it is supposed to be, or is this an error? It is almost too fast to completely understand. I realize I could bring down the speaking speed, but then other voices would be very slow. I just want to know if I am having a problem or if this is the same for everyone. Thank you to anyone who can provide some information.