Try going into nature and meditating just on the sounds you hear.   Try to hear as much as you can and sustain awareness as much as you can.  When awareness drops and you are lost in thought, bring the mind back to the sounds.  Do not judge the sounds or note them or classify them, just hear as much as possible. 

You're concentration is good, that's very good for meditation.  To broaden your awareness try a meditation where you feel your whole body.  You sit, close your eyes, and just feel all the sensations of your whole body. If your mind wonders, no problem, just bring it back to the attention of your body, if your mind wonders again, no problem, bring it back to your body.

try it!

Just thought I'd chime in with my own experience to agree with the above suggestions in terms of the broadness aspect of vision, even though strangely they are obviously related to other senses.

I have often noticed that things get very wide and panoramic sometimes, and sounds and physical sensations are probably what I focus on most. Although I meditate with eyes closed, I have often noticed the visual aspect to develop to be very broad. 

Good luck and good practising!