Asterisk with Speex at low bitrate

Hi there

I have compiled Asterisk with the Speex codec and it is working, but at a fairly bitrate. I am trying to get the bitrate down to 8kbps, and read that one can do this through a codecs.conf file, which I put in the /etc/asterisk directory. However, this does not seem to be working.

These are the instructions I followed:

I am using version 1.0.9 of Asterisk. Is the codecs.conf file still supported in this version? Am I using the right method, otherwise how do I configure speex to work at a lower bitrate?

Many thanks