You have to understand that Archer C7 is using it's CPU for both NAR/routing and also for parts of WiFi driver. Thus, if you have fast Internet connection and are using 5GHz WiFi you might run into CPU bottleneck.
What you can do is to try to enable flow offload in Firewall general settings. That will yield best throughput possible. I do not know what C7 router performance on OpenWRT is but you should be able to hit at least 500Mbit/sec routing speed with wired client. Perhaps less with WiFi.
Yhea i got this already, however the wifi is getting limited by the OC cpu aswell, wired is fine trough. I could get 500 mb's down (cable) without a problem and iperf3 between wan and client got me around 960mb's on SSF built.
I compiled own build using ath10k non-ct,. used breed bootloader to get 960mhz.
Wifi link all seems fine highest possible, running speedtest on wifi gives me 280mb's max.
Checked stock firmware and Wifi was around same 280 mb's max.
400Mbit/sec true throughput is only possible if you are using 5GHz 80Mhz wide channel with 2x2 MCS9 connection using ac protocol.
If your WiFi card is not able to utilize 80MHz, defaults to lower speed rate due to interference or router is not able to activate 80MHz due to DHS, bad channel choice or something else, speed will be lower.
By running speedtest, you are not only benchmarking WiFi, you are benchmarking whole chain from your browser, WiFi, routing/NAT, your ISP and finally, server on the internet.
In this thread, we are discussing WiFi performance only. By oc-ing the router, it is possible to reach up to 500Mbit/sec WiFi performance. And when I say WiFi performance I mean throughput between WiFi LAN and wired LAN. When using speedtest on C7 used as a router, CPU will be used to route packets between LAN/WAN (on the top of its work doing WiFi). Basically, CPU will be both processing WiFI traffic and doing WAN/LAN routing at the same time. So it is fully natural that WAN/LAN throughtput will be lower than LAN/LAN. (The speed will vary depending on how complicated routing rules are, if HW offload is enabled etc.)
In my case, Archer C7 is used as AP only (does not route anything), so I am benchmarking WiFi client to wired LAN iperf3 server only = Archer C7 CPU is used for WiFi only and routing is done by dedicated x86 router.
I have the same setup, WRT1900ACS (Main) and C7 as AP.
Last two days i have been working on creating an AP only firmware so it is stripped to the bone.
The wifi seems to be on it's best by using the ath10k-firmware-qca988x the CT is using less memory however it also has around 20/30mb's lower troughput. My Nvidia Shield is able to get around 270/300 mb's now. My pc with the Archer T9UH 1900acs adapter is getting around 250mb's. Mobile phones all around 200/250. I will see to improve the build a bit more but it's looking quite good so far!
You have to test LAN - LAN with iperf3 (one WiFi client and one wired client) in order to isolate WiFi performance. Just running speedtest from different devices towards internet does not say anything. It could be your router that is throttling, it could be your ISP etc.
Run iperf3 on wired LAN computer and test your WiFi device towards that. Report the results.
Update: I have now been running all my Archers @ 960MHz for more than four months with zero issues.
Also, I have been experimenting with different ath10k drivers and found that this combination providea highest 5GHz throughput:
(I disabled and removed all ath9k 2.4GHz drivers as I was never able to run 2.4 WLAN reliably)
This works so well that I reckon it will take very long time before I am tempted to replace those C7 AP's with 802.11ax gear It just works and provides 400Mbit/sec true data rate to "common" WiFi devices (phones iPads etc) all day long and also gives extra three GbE wired ports.
Apart from flaky 2.4GHz this is now truly mature product, working great and providing value.
If you're only using the C7 as an AP, a 2x2 phone running iperf3 with a DD-WRT installed C7v5 will hit 400-450Mbps easily.
The standard ath10k driver on OpenWRT with the same phone gets to a 370Mbps max speed.