The menacing dude in iron armor who is currently staring at you right now
Ha!

I have no idea what he would sound like, but anolysis-wise: Since his voice is the gateway of his power, he must have a large vocal range and a powerful pair of lungs. I can imagine him being able to easily shatter glasses and incapacitate his foes with a Siren-like scream, while having a voice low enough to rival Paarthurnax in his puberty.
He must be a good singer and speaker. He can be soothing and stop babies from crying when he want to. He can be powerful and booming to inspire the people around him, and he can sound menacing, speaks with thunder and his voice God-like to intimidate his enemies.