Lots of speaker datasheets give frequency response graphs, even if they are fuzzy.
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The frequency response can depend a lot on the enclosure.
You can easily create your own bode plot using a signal generator, an oscilloscope, an electret mic and preamplifier.
Connect the signal generator to the speaker, set to a sinewave of a known frequency and peak output voltage, check with a 'scope to make sure. Connect the mic to the preamplifier and connect to 'scope, record the amplitude of the waveform. Repeat the procedure for frequencies between 40Hz and 15kHz using a logarithmic frequency scale, testing the input voltage with the 'scope each time and adjust the signal generator if it changes.
Convert all the recorded voltages to dB using the sensitivity on the mic data sheet. Electret mics tend to have a flat frequency response curve, look at the data sheet and take adjust your bode plot to account for any peaks an troughs.