No the HPF works as a subsonic filter. I forgot you don't have an aftermarket headunit so you will want to set the HPF depending on your box tuning.
say you are tuned to 45 Hz:
- 45 Hz / 2 = 22.5 Hz (one octave lower)
- 22.5 Hz /2 = 11.25 Hz (half an octave lower)
So we take 45 - 11.25 = 33.75 Hz (rounded up to 34 Hz)
In other words, you set your sub-sonic to 34 hz. So that way, if there's music below the ports frequency, it gets filtered out protecting your woofer.
Always remember the subsonic filter is NOT a cut-off. It has a roll off "slope" where whatever frequency its set to will be attenuated, and the attenuation effect increases as the frequencies get lower. Thus the power to the woofer decreases at filtered frequencies, which reduces the excursion and risk of damage.