I'm trying to determine the reason for a dip in the frequency response curve of my loudspeaker. I have a loudspeaker mounted on the inside of an enclosure, and a 100mm ID tube mounted in-front of the speaker on the outside of the enclosure.
The measured frequency response is:
At roughly 4100 Hz, a large dip in the response is noted. This dip corresponds to the cut-off frequency of the (0, 1) cross mode. This leads me to believe that it has something to do with the higher-order mode propagation, but I don't understand what.
Could someone help me understand this problem please.