Will a subwoofer add depth and clarity to my system, or just bass?

Today’s post is brought to you by the letter "S".

The letter "S" has the Super Power of being able to turn singular into plural. But not always! Due to a design flaw it can only do this when used at the end of a word. Luddite Forces in the Audioverse exploit this weakness. In a typical mind-trick they say, "This is the subwoofer you are looking for." See what they did there? The original quote was, "These are not the DroidS you’re looking for." They dropped the "S"! Pulling you back, always back, to the singular.

It’s a trap!

Don’t go over to the Dark Side. Unleash the power of the letter "S". Use four subs.

Subwoofers will not add clarity to a system. They will add impact in the form of notes you can feel as well as sound stage volume.

I’m not sure of the logic behind this statement, but it is at least subtly wrong. In a small two-way system, the woofer covers both (sorta) bass and mid-range. The large excisions of the bass modulate the mid-range, since the mid-range is superimposed on a vary-ing, larger, bass excursion. This HAS to muddy and distort the mid-range. And in my listening, it does (or did, its been a while)

Beyond that, yes, it will add weight, impact and richen the timbre.
Now, all this depend son proper setup, and you need to remember that the subwoofer must be phase aligned with BOTH speakers, and that phase alignment is perfect only for one listening position. Do the math. Its worth spending some time to get the position right, and if the crossover may be varied, to find out which one integrates best with your main speakers.

I really like sub-woofer / satellite systems if all the above are observed.
Some of my fav’s from the way-back machine were Spica TC-50is and Sequerra Met-7s with a decent woofer such as an Audio Pro (about $1000, 30 years ago).
G

+1 on ML 800x for configurability
600x is $600, ported and might integrate better with ported mains

A sub MUST have 0 to 180 phase control, phase invert, 3 and 4th order slopes in addition to level and frequency.

The ML x series do and have the advantage of being adjustable from a smart phone. With the ARC microphone and Anthem Room Correction software, room faults can be somewhat mitigated.

IMO, you should roll the low end out of your mains. This effectively increases main amplifier power and makes integration with the sub easier.  Do NOT use the sub the sub internal XO. Depending on the room and sub, you may choose different frequencies. A single polypropylene, Teflon or polystyrene cap can suffice for a start. See http://www.ielogical.com/Audio/SubTerrBlues.php/

Learning to use something like REW [Room Eq Wizard http://www.roomeqwizard.com/] will pay huge dividends

Adequate low end room control is big, expensive and ugly. Judicious furniture placement and main/sub location can get you most of the way there. Just don't listen in a sparely furnished room with bare walls and floors.

I disagree that one can't hear phase in the bass. Having spent 1000s of hours in studios with time aligned monitors, getting the low end phase as good as it can be is essential. When it's not correct, kicks and snares are flabby, upright bass strolls and live orchestras have no focus.

A good sub properly integrated improves the listening experience out of all proportion to the frequency band.

The letter is "C" for correct.

@audiokinesis

Adjusting the continuous phase control provides much more than a slight amount of timing adjustment and my ears were quite capable of hearing when I had the correct phase setting. With such a range of adjustment it is possible to ruin the sound or optimize it with proper listening and technique.
Same for my car subwoofer- with time delay I was able to fine tune the proper delay relative to my main speakers and once you find the spot- car or home- the bass becomes effortless, deep, powerful and fully coherent through the range. The subwoofer then complements and works with your main speakers rather than fighting against them.  But again, the key technique was using beat pulses rather than pink noise.