Tried replacing the AiMesh node at the back of my place (relative to the main router)...

[SolidSonicTH]

I have a ZenWifi AX XT8 running back there and I put in an XT9, hoping that the enhancements would allow me to get closer to my new Internet's bandwidth (I upgraded my modem from a DOCSIS 3.0 to a 3.1 and in doing so my download speed basically doubled).

I'm not expecting to get full bandwidth but when I tested the XT8's performance I only came in at around 430 Mb/s out of a possible ~600, which seemed too low. When I was setting up the XT9 I ran a speed test while it was within line of sight of the core router (a Rapture GT-AX11000 Pro) and I got up to around 560 Mb/s, which is about what I was hoping for, but when I took it back to where I have the XT8 it dropped quite a bit (in fact I think it might be lower than the XT8 in the same spot, although I had both routers hooked up at the same time so maybe they're cross-talking - my next test will be to disable the XT8 entirely and see how the XT9 performs back there by itself).

Was I right in thinking the XT9 would give me a noticeable bump when paired with an GT-AX11000 Pro (since I believe it's able to communicate over the 160 MHz frequency put out by the 11K when the XT8 units can't) or is this too small a jump to get better AiMesh performance and I should consider a superior model if I want improved node bandwidth? I don't know the exact distance between my core router and the placement of my AiMesh node but I estimate it's about 55-60 ft. as the crow flies (and there's a second XT8 AiMesh node in between them in the hall closet).

I also don't mind repositioning the placement of the AiMesh node entirely (I have a bookshelf next to my desk that's considerably higher than the desk where the router is and it's unobstructed as opposed to directly behind a monitor), although if I resort to repositioning the router and suddenly see better speeds I also intend to see how much of an improvement the XT8 gets in that spot and, assuming that's the issue, the XT9 becomes moot and can be returned regardless.

 

[Tech9]

Your new ZenWiFi XT9 has 160MHz support on the fronthaul radio. You need clear DFS and 160MHz capable client in order to see any differences. This may only happen if the backhaul radio throughput is higher than the desired fronthaul throughput. And your new XT9 has to be connected to the main router and not the XT8 in between. In summary - unlikely to have significant real life benefits. The speeds you are getting are Wi-Fi 5 level. Not even Wi-Fi 6 at 80MHz wide channel. Perhaps the best you can get from wireless AiMesh where your devices are placed. By pushing 160MHz wide channel you are reducing the range (both fronthaul and backhaul) and lowering the reliability of the entire system (DFS).

 

[SolidSonicTH]

Oh, so the 160 MHz frequency isn't open to the backhaul? I was able to set the 5 GHz-2 radio to support 160 on the core router but I wasn't aware that the node wouldn't be able to pick it up on the backhaul.

Every node in the network is connected straight to the main router, there's no sub-nodes in my network. The 11K puts out a strong enough signal and my residence is small enough to where it always represents the optimal backhaul path. The "Storage" XT8 isn't even necessary - every wifi client would be able to operate smoothly with just the main router and the back "Office" node (and even the back node is mostly there to give everything at the back of my place an Ethernet connection - if I wanted strictly wifi outside of directly wired clients I'd only need the 11K and nothing else), I just put it in because the two XT8s were originally bought as a pair to act as my primary routing solution before I upgraded to the 11K and I didn't want it to go to waste.

 

[Tech9]

Oh, so the 160 MHz frequency isn't open to the backhaul?

This is not what I said above. Check the device specifications. XT8 supports 160MHz on 5GHz-2 radio only, XT9 supports 160MHz on 5GHz-1 and 5GH-2 radios. Otherwise the configuration 2-stream on 2.4GHz and 5GHz-1 and 4-stream on 5GHz-2 radios is unchanged.

The "Storage" XT8 isn't even necessary - every wifi client would be able to operate smoothly with just the main router and the back "Office" node

The new XT9 node in this case is not needed. The more nodes you add to wireless AiMesh the worse the performance and roaming. Keep the nodes to the minimum number needed. Send back the new XT9 if possible and move the Storage XT8 outside.

The 11K puts out a strong enough signal and my residence is small enough to where it always represents the optimal backhaul path.

The wireless speeds you are measuring (if the client is AX-class) are achievable with 80MHz wide channels on both fronthaul and backhaul. The range will increase, the retransmissions rate will drop, the latency will decrease and the system stability will be better. You are in the US (based on your other posts) and you have Ch.42 (36-48) + Ch.155 (149-161) both available in non-DFS range and with the same allowed Tx power. Tune your system for user experience and not for speed test. Don't overpay for hardware.

 

[bbunge]

Just to chime in on @Tech9 comments, please give the 5 GHz 80 Mhz bandwidth a try. Your mesh nodes and clients just may have better connection. Speed could also improve! Also set the 2.4 GHz to 20 MHz.