@cooky1257 , are you just using the internal mic or an external one? The >500Hz response looks nicely matched but the <500Hz response is out by as much as 6dB in places which, if genuine, would be quite audible? It could however just be an artefact of the measurement signal, pink noise is notorious for 'dancing around' in the bass frequencies, I find Periodic Pink Noise provides a more stable reading. IME a sine wave sweep is the most stable/accurate for LF measurements, but Pink Periodic Noise is so much more convenient as it lets you analyse the response in real time.