Has anyone added a small subwoofer to 2 channel and been thrilled with the result?

I wonder how much difference you would hear between 10" and 12" subwoofers?

stuff-jones:

At the frequency range the subwoofers activate the wavelengths are longer than your room.  That means the entire room is being pressurized with these low signals, so the sound from the resolved wavelength is coming from everywhere.

If you are sitting 10' from your speakers, frequencies above approximately 115 Hz will have wavelengths of under 10', so the direct sound (at 115Hz and higher) will reach your ears before any reflections.  As frequencies get higher, it becomes easier to pinpoint the direct sound from the speaker.

The reason for two subwoofers has more to do with cancelling resonance peaks and valleys than improved imaging.  You can set up one subwoofer to sound pretty good at a single listening position, but if you want the bass to sound better at multiple listening positions two subs, when placed properly, will be much better.  The sub frequencies will still be omni-directional, but will be distributed more evenly throughout the room.  Any directional cues are coming from mid bass tones and transient noises such as pick and finger noises.

One of the big advantages of subs is that you can move them around to adjust to your room resonance frequencies.  That is quite a bit more difficult with large, full range speakers that can handle sub-range frequencies.  With big speakers that can reproduce those sub-frequency sounds, you will need to resort to digital or acoustic room correction to level out room resonance peaks and valleys.

@stuff_jones  kahlenz provided a good explanation.  Suffice it to say that in any of my systems if there is a bass line coming from a particular spot in the soundstage it images correctly and I have no problem picking it out.  Most of the frequency range of the bass guitar is above where I have my subwoofers filtered off at (around 40 - 80 hz depending on the speakers) so most or all of it is coming through my speakers.

Everybody will expound their favourites, so there is no real right or wrong choice of make. I would imagine that as long as they are not  put on "loud" almost any make will be satisfactory and demonstrate improvement. As someone posted above, 2nd hand ones are very cheap and you can improve at no great incremental costs as you see fit. I did not believe in subwoofers some years ago, basically because I had not heard any. Now I have a minimum of 2 even in small rooms, but on VERY low.