Having been donated a slightly battered Nexus 5 as an Android M test device, I thought I'd got nothing to lose in terms of hacking it further. One of the biggest drawbacks of the otherwise still perfect '5' has been that the mono loudspeaker isn't very loud and is tinny.
Now, obviously you can't turn a small speaker into a big one, but there are things you can do to let the component produce everything it's capable of. LG's design rather muffles the Nexus 5's speaker (positioned bottom left as you look at the phone normally, or bottom right from the back), by as much as 25% in terms of volume and tone.
So, why not claw back that 25%, at the expense of a few err.... extra holes? This was originally postulated here, but I went slightly further. Again, this Nexus 5 already had scuffs and a few bits of plastic broken off, so I had nothing to lose!
Here's a pictorial representation of what I did, with the red arrows showing the new holes:
The theory is that the three extra holes in the speaker assembly (the actual component is under the 'HH." legend, i.e. that rectangular moulding) help provide a path for sound to escape through the rest of the Nexus 5 lower body, adding slightly to the volume and also providing a little bass reflex action to improve the tone.
In addition, I wondered if the small holes on the case's bottom (i.e. to let the primary sound out) were a little too small. Working purely on gut feel, I drilled two much larger holes through the plastic (probably too big, but hey!) and also removed the small rubber gasket (shown right, above), which was partially obscuring one of my new holes.*
* I left the dust filter over the output port of the original speaker, don't worry, so there's no danger of dust getting to the main speaker membrane. It was tempting to remove this as well, but that might have been a step too far in terms of leaving the component vulnerable!
The upshot of all this is that the sound output from my Nexus 5 is significantly louder and slightly deeper. Without two identical Nexus 5s to compare/test, it's hard to put a figure to it all (i.e. in dB) - in hindsight I wish I'd measured output with a sound meter before starting the drilling! But that 25% improvement I quoted above seems in the right ballpark.
The usual disclaimers apply - if you try this and break something then I'm not responsible!
PS. Getting the Nexus 5 back off is trivial, see here on YouTube, for example.