[dlss]

I am not an electrical engineer, but to answer your question it is my understanding that the diameter of a speaker is very important for sound quality, volume, and cost. This is the reason that home audio speakers aren't the size of thimbles.

I did a quick search to see if any of those issues have been talked about wrt iphones, and the top hit was http://forums.macrumors.com/showthread.php?t=761725 ("when i listen at max volume [my iphone] is really bad. my nokia N82 compared is like a audiophile system") -- which I imagine is caused by the N82 having a larger speaker positioned on the back.

[Tloewald]

Yes, and the person you're quoting is talking about the 3GS and no-one else reports the same problem.

[dlss]

http://www.anandtech.com/show/3794/the-iphone-4-review/11

Puts the iphone 4 over 3g as ~3x quieter than a nexus s over 3g. (2g is closer, but no one I know uses their iphone 4 over 2g).

From the review: "For a long while, people have complained that the iPhone [3g & 3gs]'s speakerphone volume was too quiet... I'd say the iPhone 4's speakerphone is still loud enough, though calls over 3G are still a bit too quiet. Until Apple increases the gain on 3G calls, iPhone 4 customers who are hard of hearing should invest in a bluetooth headset."