Asterisk 13 | Module CHAN_MOBILE | Sound delay

I’ve installed Asterisk 13 && FreePBX 12 with module chan_mobile.
When i make internal calls between extensions IAX / SIP it works well.
So, i connected my phone to asterisk server, configured /etc/asterisk/chan_mobile.conf

[adapter]
address=00:XX:XX:XX:XX:XX
id=ad1

[Nokia]
address=AC:XX:XX:XX:XX:XX
port=2
context=from-nokia
adapter=ad1

[Galaxy S4]
address=9C:XX:XX:XX:XX:XX
context=from-nokia
adapter=ad1
port=3

Configured /etc/asterisk/extensions_custom.conf

[from-nokia]
exten => s,1,Dial(IAX2/501)
exten => s,n,Hangup

So, when i try to call on my phone connected to Asterisk, extension 501 (IAX) rings, but when i answer, the caller hears me clearly, but with a 1-2 seconds delay. The biggest problem is that i dont hear him at all, sometimes i hear smth but very unclear…

I tried to use a SIP extension but in this case neither the caller nor i hear.

Mention: Asterisk is running on CentOS 6.6; i tested 2 mobile phones, the same issue (Nokia C7-00, Samsung Galaxy S4);

What can it be ? Maybe the codecs or smth like that???