mobile phone speaker frequency response

One thing I did today is to compare the frequency response for between desk phone speaker and the mobile phone speaker.

Below are the result

Microphone used: Yeti Blue Microphone 

Place: regular size room

Sweep tone source: 50~10KHz

Desk phone - The Polycom Phone IP650 dialing the sweep tone test number (Codec: G722).

Mobile phone - Music player to play sweep tone.

Nexus 5

Sony Z1

The Mobile phone speaker result shows nearly no response under 500 Hz. Low frequency is gone and this means it's not good for deeper human voice.

The quality of the speaker depends on it's size and housing. This is somehow the physical limitation to the mobile phone speaker cause the mobile phone are made thinner and thinner today and it's difficult to do improvement at the software side.