Why the fascination with subwoofers?


I have noticed many posts with questions about adding subwoofers to an audio system. Why the fascination with subwoofers? I guess I understand why any audiophile would want to hear more tight bass in their audio system, but why add a subwoofer to an existing audio system when they don’t always perform well, are costly, and are difficult to integrate with the many varied speakers offered. Additionally, why wouldn’t any audiophile first choose a speaker with a well designed bass driver designed, engineered and BUILT INTO that same cabinet? If anyone’s speakers were not giving enough tight bass, why wouldn’t that person sell those speakers and buy a pair that does have tight bass?
128x1282psyop
Many do try to do just that. Look around however, it quickly becomes very obvious the hardest most expensive thing you can find is two quality speakers with true 20 Hz bass. They essentially do not exist. Turns out (read on) that for reasons of physics they cannot exist. Which is why they don’t.
@millercarbon
This statement appears to be false.


My speakers at home are made by Classic Audio Loudspeakers. They are the model T-3.3.


They have a pair of 15" woofers. One of the them is the TAD 1602, which has a free air resonance of 21 Hz. Are you really trying to say that a speaker like that in a properly tuned bass reflex cabinet (my speakers are the size of refrigerators) can't go to 20Hz?? They seem to have plenty of undistorted output at 20Hz in my room.




There are phase reasons to use subs but anyone who has to ask this question is not an audiophile anyway, and this poster is only baiting and so one worm is all you get...
Great subject. Right now I am in the process of doing room treatment and my bass sounds great. But I will still add 2 subs. I have demoed a few in my room and they really open things up.  My mains have excellent base, but the lowest of frequencies are missed and I want them also. Thanks for all the info, helps alot.
++++on adding subs.
I have one of my subs near a wall and under a window in my listening room, and when I want sound on the deck I put a pair of speakers in the windows with that sub. The deck specific speakers (old KEF Q10s...great sounding things) are powered by a separate amp (a trusty 100 watt Adcom) getting its signal from the main preamp, and the sub's signal is from the indoor mains little tube amp so I have to turn the window sub up a little...I have a volume control on the outdoor amp as it's way hotter than the indoor speaker's amp...all of this works very well, and unlike mapman I get my deck bass goin' which is good for the plants and lets my neighbors know I'm having more fun than they are. 
Full range cabinets are going to be rather large.  It can be much more convenient to go with smaller speakers plus a sub in a less conspicuous spot in the room. 

My understanding is that having the deep bass coming from more than one speaker invites phase cancellation.  

I assume that taking the deep bass out of the speaker handling the low mids and bass frequencies will help to make the audio clearer.