The M9+ was run through our Wi-Fi System test process, letting it use whichever channels and bandwidth it chose. It used 2.4 GHz channels 4 & 6 (40 MHz bandwidth) and 5 GHz channel 44 as the primary channel with 80 MHz bandwidth for both nodes. A quick check with a Wi-Fi scanner app showed channel 149 used by the upper band 5 GHz radio. This radio had a hidden SSID, so was not available for client connection.
I should note that TP-Link sent a three-node version of the product for review. But since the only product sold right now is a two-node version, that's the configuration I tested. TP-Link said the three-pack is coming "later this year", with pricing expected around $450.
Here's what M9+ looked like in the octoBox 18" test chamber.
M9+ in test chamber
Throughput vs. Attenuation (RvR)
The Rate vs. Range or RvR benchmarks look at how throughput varies with decreasing signal. This test is done on the root node, so is a best-case view and does not include any effects from backhaul links.
I sometimes have to add 9 dB of attenuation when running 2.4 GHz tests so that the octoScope Pal reference client's -30 dBm maximum recommended input level is not exceeded. This was not the case with M9+; no additional 2.4 GHz attenuation was applied.
The 2.4 GHz downlink plot shows the M9+ with the lowest throughput of the group. This is likely caused by the M9+ receive link rate of 300 Mbps vs. 400 Mbps for the Deco M5. Both products used a transmit 400 Mbps link rate (with strong signals)
Throughput vs. Attenuation - 2.4 GHz downlink
2.4 GHz uplink show narrower gap between the M9+ and other two products. But the M9+ still tracked lower for most of the test run.
Throughput vs. Attenuation - 2.4 GHz uplink
5 GHz downlink shows a turnabout with the M9+ running above the other two products until it drops below Orbi at 33 dB attenuation.
Throughput vs. Attenuation - 5 GHz downlink
5 GHz uplink shows similar results, with the M9+ beating the Deco M5 and Orbi until the 33 dB attenuation test.
Throughput vs. Attenuation - 5 GHz uplink
Backhaul tests run traffic between the root node LAN-side Ethernet port and the Ethernet port on each leaf mesh node. To me, this is the most reliable predictor of how a product will perform in the other benchmarks. A mesh node can, at best, only pass on received throughput to connected clients, i.e. low throughput in, low throughput out. Since I tested only a two-node system, I have only one-hop results to show.
First hop backhaul downlink bandwidth of 395 Mbps is just behind Orbi @ 399 Mbps and almost 100 Mbps more than Deco M5 @ 300 Mbps. Uplink bandwidth was notably lower for all three products, but the M9+ dropped the most, down to 257 Mbps.