You could use test tones and a voltmeter/o-scope. That would be pretty time consuming.
The easier way would be to use a calibrated microphone and measure the acoustic response of the speaker. Although you'll be measuring the combined response of the speaker, the acoustic environment, and the electric filters - this would be the preferred way.
The easier way would be to use a calibrated microphone and measure the acoustic response of the speaker. Although you'll be measuring the combined response of the speaker, the acoustic environment, and the electric filters - this would be the preferred way.