Get a USB measurement mic from Dayton Audio and REW software for speaker measurements.
Use the mic calibration file in REW to correct for the mic frequency response. Typically, the 0 deg calibration file is available for use.
Other mics like the Beyerdynamic MM-1 XLR phantom powered mic has both the 0 deg for quasi-anechoic and 90 deg for room measurement calibration files.