I asked this question on D-Links forums also but I figured I try here too.
"I have my first install up and running for a week now. There are a handful of issues I'm working on that I hope I can get some help with.
The first one I'm looking for help on is internal intercom calls. This customer is used to their old pbx system and have become used to speakerphone/speakerphone internal intercom calls. When they do this with the new RP system, they get horrible feedback and echoing. One user has to pick up a handset to even make communication possible.
Are there any settings that can help this? I have one ClearOne Max IP RP phone that I put in the owners office and it works much better. This isn't a viable solution for all users though.
The rest of the system is D-Link Base, two D-Link gateways (5 lines),13 D-Link Phones and One Aastra 6757i CT RP phone.
My suggestion is - work with D-Link on the D-Link specific voice quality issues/echo/speakerphone, etc...
With regards to speakerphone quality, you mentioned that the issue doesn't seem to occur on the ClearOne. I'm curious if you have tried your testing on the Aastra 57i that you mentioned that is also part of the configuration? Aastra phones (in our observation) appear to have the best built-in speakerphones of all of the RP Hardware to date, with the exception of the ClearOne which is of course, a premium conferencing phone designed specifically for that purpose (conferencing).
I did some testing with the 57i but it's hard to get definative results since I only have one of them and one end is either a D-link or the clear one.
It did seem a little better though.
The thing I noticed about the D-Link during an internal speakerphone call is that there is zero noise canceling. The mic and speaker are both wide open all the time. During an outside call, the gateway takes care of the echo canceling apparently (if the echo cancel setting is enabled). I will do as you suggest and see what I can do with D-Link directly.