Shortly after we posted the Archer C9 review, TP-LINK let us know our results didn't match what they found with testing in their own Octoscope-based test setup. The culprit was that the C9's stand-up format positioned a good portion of the router's antennas above our test chamber antennas, reducing received signal. This is clearly seen in the test setup photo below.
TP-LINK Archer C9 in test chamber - original test
A quick retest with the router laid down so that all parts of its antennas were lower did in fact show significant improvement.
TP-LINK Archer C9 in test chamber - retest
So we went back and reran wireless tests for all stand-up format routers to ensure we were not unfairly penalizing them.
The firmwares and routers in this retest are:
- ASUS RT-AC68U: 188.8.131.52.378_3873
- ASUS RT-AC68P: 184.108.40.206.378_3873
- Buffalo WXR-1900DHP: 2.3.0
- Linksys EA9200: Ver.1.1.5 (Build 164615)
- TP-LINK Archer C8: 3.16.28 Build 20141023
- TP-LINK Archer C9: 3.15.27 Build 20141015
The retest improved 5 GHz performance in most cases. But 2.4 GHz performance was either essentially the same or slightly degraded.
The affected routers fall into AC1750, AC1900 and AC3200 classes. So that's how we'll compare before and after.
TP-LINK's Archer C8 definitely benefited from the retest, moving from #3 to #1 rank among AC1750 class routers tested with the current process.
AC1750 Ranking Comparison
The C8's performance summary shows strong 5 GHz performance helped boost its ranking.
TP-LINK Archer C8 Ranker Performance Summary
This is clearly seen comparing 5 GHz downlink throughput vs. attenuation plots of the top four ranked routers. Not only does the C8's overall throughput curve move higher, but it remains connected out to 39 dB of attenuation.
5 GHz downlink throughput vs. attenuation comparison - AC1750
5 GHz uplink throughput isn't as dramatic, but improves mostly with lower attenuation levels (stronger signals). Check the gallery below for a full set of before and after plots.