Below the tuning frequency a sub will "unload" causing distortion. A Hi-Pass filter controls this.non-linearity may happen with tuning below fs.
It's apparent from the above statement the author has never heard a large low tuned ported sub.If you try tuning below Fs, then all you get is high distortion and poor output
well I got what I wanted out of your thread, Fred. I hope you did as well. Research... you got it! You are now infected!There is no problem tuning below driver Fs - this does not create excess distortion. It's a myth just like so many other porting myths. Check Ilkka's measurements of the SVS Pb Ultra 13 tuned to 15hz to confirm.
Thing to remember is that the nature of harmonic distortion (which, by definition, just about any nonlinear distortion will create) is that higher frequencies are created where there should be none. And those products, even while absolutely smaller in scale, can often be perceived to be even louder than the fundamental. Of course there are then real signals that offer other sounds to mask and such, but still...In your experience, are the signs of stress quite subtle, or more obvious? My guess is subtle because of the nature of hearing and our lack of sensitivity down low.