@Kevin_Z 

Yes tried and verified, Asus rt87 acu router and Sitecom Greyhound, both were part of my previous setup and no noise troubles there. Not in group or in single speaker play.

Thing is, we as users all determined that it's a to link issue, soft or hardware, but that's something u guys need to find out.

On average the m9 performs good, but has its flaws because we need to switch off some of the settings according to u guys. 

Please resolve the problems, so we can use the mesh system to it's full potential.

@Kevin_Z 

I have the idea that for the AC1200 this could be the problem: "Optimize the solution to solve the wireless issue caused by Android devices’ unreasonable behavior." https://www.tp-link.com/en/support/download/archer-c1200/#Firmware

I've bought two new routers and will sell my two tplink routers, as this problem is very annoying..

The same issue popped up here, but with a Harman Kardon Citation One duoset. Solo they perform great, but when paired as a speakerset or both in a group the crackling is terrible. I've brought back the first set and got a brand new one. Exactly the same issue. When I install the speakers over a mobile hotspot, they work perfectly as a stereo pair. After hours of troubleshooting, the problem is isolated to the Deco M9.

I spoke to a tech guy from Harman Kardon, he asked me to check the following:

- UPnP must be enabled --> this is default in the M9?

- If possible, activate Multicast --> can't find anything

I'm worried if this can be fixed. Otherwise I'll have to return the Citation One speakers.

Is there any sight on a solution?

@Martinnn 

omg omg.... could it be a TP-link fault? Ive tested jbl link 20, jbl link 500 and citation one and all had problems with crackling... so I returned them. All the time I thougth it was bad speaker quality but now youre telling me it is the Deco M9 that is the problem. Ive got google speakers that works perfect though. However Tp-link you need to take a look at this. Im very satisfied with the DECO regarding all other things... but this is not acceptable.

I have been putting up with the same crackling sound for almost year with my JBL Link, and chromecast audio devices, and JBL Playlist.  They were working well before and all of a sudden crackling sound appears.

Tracing back, it happens right after I changed to Deco M9 Plus. I have always thought its JBL, and Chromecast Audio, or a combination of which when playing as a group, but after having read the number of people having similar problem, I tried reverting back to my old router and the crackling sound do go away.  The crackling sound persists for me even if I am just playing on a single JBL speaker or chromecast audio device.  The only time the music does not crack is using only Google Mini. 

So I am quite certain this problem is due Deco M9 plus.  A friend of mine has exactly the same setup with me but is using Orbi mesh, no crackling sound whatsoever since day one.

I urge TP-Link to take a serious look at this and fix the issue with a software upgrade or else you will be losing customers, future and present.

And finally, no, the suggested solution of disenabling priority and using standard qos does not work at all, so TP-Link, please do not suggest this again and just get on with fixing the issue.

@Kevin_Z 

Is this huge problem under investigation?

I have newly bought and installed the Deco M9 Plus system, I have all the problems mentioned above, and tried all the "fixes".

If there is no solution in sight, I am sure I can return the equipment and buy something that works.

Please let me know if you are working on it.

@Gert2  as tplink has not responded anymore, it's safe to say, they don't care about the problems we as users encounter.

It shouldn't be a big problem for them to fix, as other manufacturers don't have these problems.

I really am investigating on how I can build a liability case, because this was not mentioned when I bought this set. And I want to be able to fully enjoy a mesh setup with Al the ittt and iot in and around my house.

I can't advise u to return the product, but I Shure wish I could return mine, without having any costs.