Yeah I know I'm really late on this topic, but it is interesting. Not to be a buzz kill, but the audio guy originally mentioned was partially right although he probably doesn't know it or why. No sub, no matter what size or make (not even the rotary sub) can porduce audible tones below 20hz. Now, I love feeling and seeing a sub hit the low lows but for the most part' that is all it is; seeing it and not hearing it. I know, I know everyone knows a guy or saw a guy hit like 160db on termlab at 20hz but you did not "hear" the tone. What you actually "heard" would have been a combination the vehicle shaking and the voicecoil sliding along the former. Not to mention that the sensor used with termpro does not register acoustic energy (actual sound waves), it registers turbulance or pressure created by acoustic energy. The best analog for this would be a tsunami. You may not feel the event (the earthquake or landslide) that created the wave, but the wave can still be registered. I will agree that most shops employ dregs that have no idea what a quality product is or why it is better than another. Nowadays with all of the subsonic filters to keep 10hz and below tones out of the reach of the masses, who will push a speaker to its' wattage limits in order to see the excursion of a sub bass tone while heating the voil coils to melting point and eventually killing the sub, it is difficult at best get accurate tonal reproductions below 20hz not due to the subs but due to the audio processors built into most of the other equipment. With that said let the hate mail begin... be gentle.