Mix old AV2 with new AV2?

[Logic Bus]

I own four (two sets of two) Linksys PLEK500.

Since I got them, powerline adapters have gotten faster. I'm considering one set of Netgear PPLP1200-100PAS.
Here's the question: will mixing ~500 Mbps adapters with ~1200 Mbps adapters limit the speed between the two ~1200 Mbps adapters? Will all the adapters drop down to the lowest speed? (I could eliminate the older adapters if necessary.) Does anyone currently have a mix of older and newer adapters?

Secondary question: With my PLEK500 setup, I currently get over 100 Mbps between two adapters in my basement (PC on one side of the room, Xbox, TV, Apple TV on the other), but I max out around 35 Mbps between my PC and the router (which is on ground level). Can I expect significant improvement with the PLP1200-100PAS?

Side note: A few months ago I upgraded my router from a D-Link DIR-655 to an Asus RT-AC68P. Wireless is better but for some reason my PC's Speedtest.net went down from about 50 Mbps down to 35 Mbps down. I've never determined the cause of the speed drop. (I even posted about it on snbforums.) My best guess is noise but I tried testing speed between the adapters with nothing plugged in at the router's adapter (not even the router) but I didn't see improvement.

 

[thiggins]

All powerline adapters share the same frequency band. So behavior is similar to mixing slower and faster class wireless adapters. To transfer the same amount of data, slower adapters need more "air" time than faster adapters.

If slower and faster adapters are communicating, transfer will occur at the slower rate.

If you have both pairs of adapters simultaneously active communicating with each other, the faster pair will drop somewhere between its maximum rate and the slower pair maximum rate.

If pairs of adapters are not operating simultaneously, each will operate at its normal rate.

As to improvement with the PLP1200, it's possible. Under the same conditions we measured 137 Mbps average downlink throughput with the PLEK500 and 213 Mbps with the NETGEAR PL1200.

To your last question, noise at the receive end of a powerline connection has more efffect due to lower signal-to-noise ration.