hdaudio: Why external speaker doesn't work though headphone does?

[Mayuresh <mayuresh%acm.org@localhost>]

I am using NetBSD 5.1.

On my laptop hdaudio driver produces sound if I connect headphones.

I have same hardware (ICH8) on a desktop. However connecting an external
speaker does not work with hdaudio here.

From hardware and driver's point of view, what is the difference between
these two setups so that one works and the other doesn't?

(Both hardwares are fine. They work on Linux.)

Mayuresh.