What does a subwoofer solve?

A subwoofer compensates for a human ear’s reduced sensitivity to the bass frequencies as demonstrated by the Fletcher & Munson curves.... as was the 'loudness' control of the older vintage amplifiers.

Perhaps try an amp that doubles down in wattage from 8 ohm to 4 ohm. Then again to 2 ohm. There are not a huge amount of options out there but there are a few.

I just cannot understand how a single speaker can help to improve my appreciation of the stereo sound. I have tried a subwoofer and all it did was confuse me.              I have two Audiolab mono 8300 amps. I use a Naim dac to organise the sound and produce a very good system. My Aria 926 speakers do a good job and the stereo separation is wonderful. However, when I add a sub-woofer, the sound is confused as all of a sudden , I can`t tell where the sound is coming from. To me a sub woofer makes up for the poor response that the speakers do in low frequencies. But when you add just one extra speaker, the result is ruined by a lack of separation. I can understand 2x sub -woofers, but not just one. Can someone comment on this., as I just don`t understand the reason for one sub-woofer.

When I listened to my system without a subwoofer I was pleased and could clearly hear stereo separation. But I had heard other systems whereby I heard much deeper frequencies in the music. In those systems I could not always place the lower notes/sounds/instruments but I was surprised I heard that musical information I was missing on my own stereo system. Once I bought one, then two subwoofers I had that same effect. But I do agree, at some point, usually when one spends over $5 to $8k you can get true full range sound from stereo speakers. I do agree with many people commenting here that proper integration with sub and speakers that play well together is key.

Assuming that a quality subwoofer is properly set up as it is added into your system: 

- it will remove the lowest frequencies (the deep bass) from your main speakers so that they no longer have to do all of the dirty work. The deep bass will instead be dealt with by the subwoofer. The #1 benefit of adding a high quality subwoofer to your system is not how it further extends the bass response, but how it can dramatically improve the sound of your existing power amp and main speakers from the midrange on up.
 

- That is by far the most compelling reason to add a sub to your high-end music system. Once your main speakers are freed from the burden of making deep bass, they will sound cleaner, faster and clearer, especially in the midrange and midbass.

- They will also image way better because there will be far less air pressure and therefore resonance and vibration affecting their cabinet walls.

- And since the power required to make the deep bass is provided by the subwoofer’s built-in amplifier, your main power amp will be free from that burden and begin to sound like a much more powerful amplifier