Poor volume with Bose headphones

Most likely the Bose need more power -- many portable MP3 players do not generate enough volume to drive quality headphones.

Usual best bet is to add a headphone amplifier -- it will do lots of things, including making the sound much, much better. I use one from Headroom, the leader in this area. Here's a good place to start:

http://www.headphone.com/products/headphone-amps/

Assuming you are using a QC2 or QC3. If it is not one of these then you need an external amplifier, as others have said.

If you have an original Bose QC2/3 headset and cord there is a switch on the end of the cord that goes into the headset. Pull the cord out of the headset and make sure the switch is set to the "Hi" position.

Bose also makes a replacement cord specifically for the iPhone. If you have purchased one of these cords the volume should be quite loud, as the Bose has a built in amplifier.

In either case make sure the battery in the headset is fresh.

Most likely the impedance load of the Bose headphones is too much for the iPhone to push. MP3 player headphones really cant be above about 60 ohms.

Which is just another way of saying what I said -- like I said, get the headphone amp and you'll be fine.

Not quite, but the result is the same.

You need a headphone amp.