For those who are not familiar with the Speex Voice Codec, I can assure you it will dramaticly increase the voice quality in the game server. If you are wanting to use the speex codec, simply use the following CVAR:

sv_voicecodec voice_speex

And use the following cvar to choose which voice quality you want to use:

sv_voicequality 1 : 2400bps, lowest quality
sv_voicequality 2 : 6000bps
sv_voicequality 3 : 8000bps
sv_voicequality 4 : 11200bps
sv_voicequality 5 : 15200bps, highest quality

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You can also put this in servers.cfg, as example:

sv_voicecodec voice_speex
sv_voicequality 3

remember to only use one sv_voicequality 1-5 command, not all 5 .. Trust me, your voice will be crystal clear in game.

Speex has been in the HL engine for quite awhile now. Surprises me that most people still use Miles.

So am I. But not a lot of people are familiar with it nor the commands though.