My Phone Power Grandstream HT502 adapter is connected between my Mac and my cable modem. With the adapter installed, my internet broadband connect speeds range from 100-197 K. Remove the adapter and connect my Mac directly to my cable modem and my speeds increase to 3.5 - 5 Meg. Phone Power tech support hasn't been much help. They just keep sending me questions and never seem to act to fix the problem. A good company would have immediately sent me a new box to start with. Any configuration suggestions or a recommendation for a new VOIP provider?
You might want to get a router. It would plug into your modem. Your Mac and the PhonePower Grandstream would plug into the router. That way your Mac's connection speed will not be degraded by having the Grandstream in between.
I believe most of us use this configuration. I do.
The Grandstream has a the ability to limit bandwidth in both directions. The only issue being that by default it is set to wide open. Can you PM me your account information that way I can look into the issue?