How to measure the frequency response

Hi all,
I just purchased a pair of vintage speakers and a Sunfire Subwoofer, but I do not know what the speakers actual frequency response is (I received no instructions, and there's no mention of this on the back of the speakers, only the impedance, 4 ohms), to be able to pair them with the subwoofer.
If anyone has a suggestion on what to do or how to measure the FR of these monitors, I will be very grateful.
Thanks so much
Mario