The Alpha 10 can be used in the midhorn. Compare the response curves of the midhorn below. One is a measurement using a Delta 10, the other using an Alpha 10. Disregard the amplitude because microphone distance and preamp gain were different. Both have average sensitivity of 106dB/W/M. Just pay attention to the overall response curves.
π Midhorn with Eminence Delta 10
π Midhorn with Eminence Alpha 10