The above impulse response is from a large 3 way speaker with time aligned drivers and strict 1st order crossovers

Note the reflection at 2.5ms and the room reverberent field starting to build up after 3.5ms. The frequency response in anechoic conditions is obtained by selecting the impulse from 0 to 2.5ms, eliminating the reflection, and then opening the spectrum analyzer in Audacity.

Misaligned drivers or higher order crossovers will produce gross distortion of the impulse shape.

Resulting Spectrum using Audacity

This uses the first 2ms of the above impulse with an extra 1ms of silence added before the start of the impulse to pad out the sample length to around 128.