Run Down time.
The 2DS has one speaker, about as big as the middle of the D-Pad (9 Dots in a Square-Shape) in the top-right of the system, and it's best at Mono, but Stereo is also supported (I stay Mono to keep the Audio from getting any worse, and trust me, it gets worse in Stereo)
And as such, the sound quality is pretty bad, but not terrible. It still runs the game you're currently playing's OST and SFX smoothly, but watching things from Youtube has pretty bad quality unless the recorder is really good (hence why I watch Chuggaa alot more than my other channels, sorry Yoshiller)
And I have to put up with that massive downfall in Audio Quality for all eternity (or, atleast, until the New 2DS comes out, yes I'm that poor)
Well, considering how heavy stereo is used, I do consider mono bad.
In fact, mono is fine for old games (n64 has only slight but neat stereo and snes is where it started to have some) or if the music was made to work in mono which most of the time is not the case.
For example, you know the famicon startup music in TTYD?
Even audacity recognise it as a mono track so, here, it's fine on mono (stereo won't change anything).
But games like pokemon or even paper mario since TTYD, stereo is heavily important. In TTYD, some music feels immersive enough to feel outside of my ears and that's only because of high sfx on the music put strategically on the extreme side of the channels. Remove it and you loose a ton of quality. I actually wonder what's worse between playing a stereo designed music on mono or playing it back on youtube?
Because the thing is, compression makes stereo less apparent and less usefull in general, but you still CAN perceive them, just less (but for me, enough to not worth it).
So, if the music sounds fine on mono, it will, but you loose a ton withtout it and especially if you use headphones. I rarely use speakers because headphones allows me to have a better sense of the stereo effects.
sometime, it could totally waste a whole ost experience. Pokem on black/white 2 (not the first) completely revolves on stereo and the ost goes crazy on it. The music I heard that used it the most was the shadow triad encounter theme. It basically plays a part in one ear, the following in another, other, and it will keep getting faster and faster between switches. The kyurem battle theme is literally a constant ear switch. Seriously, that's actually why I loved this ost, but play it on mono, you get that yes, the music is good, but you loose so much.
it's weird how stereo works here btw. I hope they don't put both signals and emulate it because that is indeed not that great...
n64 music I tell you, you don't loose much. GC games like TTYD however, that's a complete different story. Trust me, ssbm is so much better on stereo.
But still, why don't you have a sound chip? I wonder if it broke or you simply (and I don't know it could exist) bought the pc without it?