Bass-reflex : is the vent sounding so poor ?
In a bass-reflex box, sound from the rear of the speaker chassis is re-radiating through the port, Rod Elliot measured values between -10 to -20dB up to 3kHz, about same figures in Borwick’s book. So I did a simple soft to listen if this sound is audible or not. I also added a simulation for the 24dB/oct cutoff of this kind of box, so you can listen if the cutoff and its associated group-delay is audible. Listen with a headphone and not through your favorite bass-reflex box or you may add distortion two times !
Next step would be to add re-radiation from the enclosure through the cone itself (values seem to be in the -20dB range).
The soft is at the download page.