Do you use a Subwoofer when listening to stereo?

The quick answer:
No, I don't - its why I don't have one sub in the first place. 
Why?
1. Due to very favourable room conditions, my floors standers going down to quoted 35Hz are just fine as they already 'borderline', at times, tend overload the venue. 
2. Having had some exposure to only marginally integrated subs, leaves me to keep my wishes clear of any subs rocking my guts. (I'm not into 'thunder and lighting' AV shows either.)
So, 'Horses for courses' I'd say. 
M. 🇿🇦 

" Nobil100, no it is not fine to run satellites full range while adding subs for three reasons. First is you miss the opportunity to lower distortion and increase head room significantly in the satellites."

Hello mijostyn,

     I googled emergingsoul’s stated main speakers, B&W 804 D3, before I made any comments on his thread and these are what came up:

https://www.bowerswilkins.com/home-audio/804-d3

     These are the floor standing, full range satellites my comments were based on and they have a rated bass extension down to 24 Hz. Just like any pair of floorstanding speakers, of course, I realize it’s highly unlikely that their rated bass extension will be heard or perceived at the designated listening position without the utilization of at least 1 properly positioned and configured sub in the room.
     Apparently, you’re under the impression he has stand mounted bookshelf type satellites with limited low frequency output. If this were the case, then I’d agree with most of what you stated. But I definitely don’t agree with your statement:

" Unless you are using digital bass management matching phase and time are difficult, usually by trial and error moving the speakers and perhaps by using a phase control on the sub."

     Your statement is incorrect because bass sound waves are extremely long, spread out in all directions from the driver, whether the woofer is in a main speaker or a sub, and they continue to reflect off room boundaries (walls, ceiling and floor) until they’re either absorbed or run out of energy.
     In fact, we don’t even hear or perceive any bass sound at all until the very long complete full cycle bass sound wave is detected by our ears/brain. If we detect anything other than a complete full cycle sound wave, we hear or perceive any sound at all. If the room is not very large, this means the very long full cycle bass sound wave must reflect off of 1 or more room boundaries before it is even recognized by our ears/brain as such and a perception of sound generated by our brain.
     The truth is, much of the deep bass sound we hear in a room is typically perceived as a result of reflected, and not direct, sound waves. Given these physical realities in most normal sized rooms, it’s obviously not possible to time align over the entire audible frequency range.
     It’s virtually impossible to ensure that the long and omnidirectional bass sound waves arrive at the designated listening position at the same time that the much shorter and highly directional midrange and treble sound waves arrive, Fortunately, it’s not relevant since humans don’t require time alignment for accurate sound perception.
     In regards to matching phase, your statement is more accurate. However, it’s also true that inverting the phase on a single sub, in a room with multiple subs, can improve perceived bass performance.

Tim

I agree with @noble100 
If your speakers are generally of the full range variety, no need to add an additional electronic crossover to the mix. KISS applies here, less electronic artifacts, the better.

Oz

it is not fine to run satellites full range while adding subs for three reasons. First is you miss the opportunity to lower distortion and increase head room significantly in the satellites. Second is you make integration much more difficult. You are down where the wavelengths are over 10 feet up to 30 feet. Unless you are using digital bass management matching phase and time are difficult, usually by trial and error moving the speakers and perhaps by using a phase control on the sub. Without a two way crossover there will be more overlap making the problem worse.

I get the part about distortion and headroom in the mains (which you are calling 'satellites'). Its an issue that has concerned me. But as far as getting matching time and phase, below 80Hz its simply not a thing. The reason why has been explained here several times so I'm not going to repeat it.

I ordered a pair of the Swarm subs to supplement my Classic Audio Loudspeakers which are flat to 20 Hz. The problem is I have a standing wave at the listening chair and too much bass elsewhere. So I only need two subs and I got Swarms since they are designed to operate inside the room boundary effect. I need them to be against the walls out of the way. Here are the instructions Duke sent along. When you look at his comments, its obvious that all the things that you are commenting about are on his mind as well, but are easily solved without resorting to DSP:

You MIGHT try this: Start the subwoofer amp's phase control at 90 degrees (that may change later in the process), and wire the two subs
in opposite polarity from one another. This will tend to prevent them from making the low bass region too loud, while they are improving
the in-room bass smoothness. If the two Swarm subs are to the left and right of the listening area, this may also increase the sense of
immersion in a large acoustic space.

I normally leave the 18 Hz protective highpass filter ON, but that's up to you. Also, have the "Bass Boost" off. These controls are
on the back of the amp.

As a suggested starting point, going from left to right across the front of the subwoofer amp,
first the EQ: Frequency 18; Bandwidth .1; Level "0". This effectively turns the EQ "off", so it's in reserve in case we need it.

Next the other controls: Phase 90 degrees; Frequency 10:00 (about 75 Hz); and Gain at 11:00.

If you are going to be "dialing in" the subs by ear, here is the sequence of events that I suggest (you can also use this sequence
if you're using measurements):

1. First, adjust the Gain for best sound. This is the control which will make the most difference.

2. Next, adjust the Frequency. This will make the next most difference.

3. Cycle back through Gain and Frequency at least once.

4. Adjust the Phase. This will make the least amount of difference.

5. If there is too much bottom end, try plugging one port, and then unplug that one and try plugging the other.
If it's still too much, plug 'em both.

6. If there is not enough at the bottom end, try putting both subs back in "normal" polarity. If you lose smoothness from doing
this, go back to having one in reversed polarity and plan on using the single band of parametric EQ.

7. If there is still a problem area, OR if you need to boost the very bottom end, use the parametric EQ. Unless you have
measurements, expect some trial-and-error.

8. Cycle back through Gain - Frequency - Phase one last time.

It may still take several days before the Gain is dialed in exactly right. There are two reasons for this. First, the ear is
especially sensitive to changes in SPL in the bass region, so a small change makes a larger perceptual difference than you would
have expected. Second, the little knobs on that Dayton Audio amplifier are maddeningly small, so it's real easy to move the knob
more than you intended.

Having had some exposure to only marginally integrated subs, leaves me to keep my wishes clear of any subs rocking my guts. (I'm not into 'thunder and lighting' AV shows either.) So, 'Horses for courses' I'd say.

@justmetoo — I’d say you’d do well to go hear a system with well integrated subs as you’re completely missing (and mis-categorizing) the benefits they can provide.  And subs could also actually help alleviate the slight bass overload issue you’re experiencing.  Keep an open mind on this and you might be rewarded greatly.