OK here goes.
The reason the freq. response specs are separate is that the +/-3db reading lets you know that the speaker can go down to 60Hz without dropping in loudness by more than 3db. While the speaker does have output at 50Hz, that's at a -9db level -- which is a very significant drop in loudness.
You have the SPL measurement setup correct. 1 watt of power is applied and a mic is placed 1 meter away from the speaker. The anechoic measurement lets you know how efficient the speaker is without assistance from room interactions, and the in room measurment lets you know how efficient it can be in a typical room.
Are you sassified?
