Sonos network dropouts and cutouts traced to nearby Chromecast2 Guest Mode being enabled

  • 3 February 2017
  • 2 replies

I've enjoyed using a Sonos system for years, and it just started to cut out recently on streamed music and music from my NAS drive. I'd get the "Unable to Play XYZ - network connection speed insufficient to maintain playback buffer" often, but not always as it would sometimes just quit or reset without a message. I greatly appreciated the Sonos mesh network so I wouldn't need to run wires around the house, enjoy digital music sources, and be able to control and enjoy my existing speakers and amplifiers.

Extensive troubleshooting traced my problem to interference on the Sonos wireless mesh network. While my one wired Connect had no issues (cabled to router), the wirelessly connected 'Connect' and a Play5 on the Sonos mesh network were the only devices experiencing cutouts. I tried moving the Sonos from Channel 6 to 1 to 11 to no avail . I tried moving my router 2.4 GHz channel as far away as possible from the Sonos channel; I took it off the default auto mode where it tries to find the best channel. It did seem to help at times, but the cutouts would always eventually come back and would actually be more frequent (later I explain why I think this happens). I moved sources of potential interference away from the Sonos devices, but it didn't solve the problem.

I got an Android device with a Wifi Scanner (a free app) to investigate interference further on the 2.4 GHz band. I discovered 2 surprising things: First, it's been a few years since I last measured wifi levels around me, but the traffic on the 2.4 GHz bands has skyrocketed not only with my neighbors, but with cable providers - xfinitywifi on channels 1,6,11 - all strong signals that rival my in-house wifi - all this competes with the Sonos mesh network on the same/similar band. I noticed some transmitters of wifi jump around channels presumably seeking the least interference, just like my router's default setting.

Second, I found an extremely high signal coming from my Chromecast2 nearby one of my Sonos Connects. It took me awhile to find the source as it's SSID is not broadcast. When Chromecast2 first is configured, it sends out a strong 2.4 GHz signal much like a wifi access point - a source of interference for Sonos mesh network. There is a similar signal sent out when enabling "Guest Mode" on Chromecast2 to allow guests to use the Chromecast2 using a simple PIN shown on the screen. I enabled this when I set up Chromecast2, but I didn't understand it would enable a wifi signal (2.4 GHz) to be continuously emitted.

I was under the impression the Chromecast2 was mostly a receiver in operation and not a transmitter, thus wasn't concerned it was near my Sonos Connect handling my HDTV audio and living room music.

Why suddenly did this start creating problems for me after years of trouble free operation? I don't know for sure, but firmware updates have come out, and I noticed the added sources of 2.4 GHz interference that dynamically move around seeking channels with the least interference including my own wifi router. I moved my wifi channel from 11 to 1, and set my Sonos to channel 11 (as far apart as possible to try and avoid interference), but the external wifi sources would start moving to channel 11, presumably to find less interference. I observed this behavior on the wifi scanner. That traffic, coming from various angles and directions, I imagine isn't good competing with the Sonos mesh system on channel 11.

So my advice to anyone troubleshooting a Sonos network signal problem is to look for a Chromecast2 nearby and be sure it's not had Guest Mode enabled. Also, do get an Android phone or tablet and use the Wifi Scanner (free) on the 2.4 GHz band and look for strong signals near a wireless Sonos device. You might be surprised some of our IoT devices are now putting out unexpected and strong wifi signals.

I moved as many of my devices to 5 GHz band as possible and turned off Chromecast2 Guest Mode. I observed most external 2,4 GHz sources "battling" for channels 1 and 11, so I set Sonos to channel 6. Now, the only cutouts I have observed are from when I am troubleshooting and reseting my Chromecast2 device - this is expected as it sends out a transmission during configuration.

I hope this helps others in their troubleshooting. With the added IoT devices, this is only going to get worse especially if you live close to many neighbors.

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2 replies

A follow-up and clarification to my post:

The Sonos wifi mesh network (channel 1,6,11) doesn't show up on wifi scanners. Hence, if your wifi router is trying to optimize the channel it uses to the least traffic, it can land right on top of the Sonos channel. I've read Sonos uses a slightly different set of specifications that don't get detected by many 2.4 GHz 802.11 devices, so that may explain why it doesn't get detected. However, the electromagnetic radio signals will at some point interfere and degrade each other since they share common frequencies So, in my post, when I moved my home wifi 2.4 GHz to channel 1, the external neighbor wifi's migrated away from channel 1 to channel 6 and 11 (mostly).

My own wifi by default was seeking out the least interference channel, and since it cannot see the Sonos, it at times would set itself to the same (or close by) Sonos channel and interfere. When I manually set my wifi to channel 1 to avoid interference and set Sonos to channel 11 to reduce possibility of interference, I noticed the outside (neighboring) wifi's moving to channels 6 and 11 (11 mostly) in response to avoid interference with my home wifi on channel 1. This made things a bit worse for me - one of my Sonos components is near a weaker part of the mesh network and closer to external wifi sources which have now migrated to interfere more on channel 6 and 11.

The solution for me was to first find a channel for my home wifi that was least used, it turned out channel 2 was the best. Then I observed how the external wifi's responded: they tended to settle on channel 1 and 11 as the strongest competitors. That meant channel 6 was best for my Sonos mesh network and I set it accordingly. There is a slight overlap here since setting my home wifi to channel 2 and Sonos channel 6 a bit too close (ideally, need 5 channel or more separation), however there is some physical separation from my home wifi transmitter to my nearest Sonos, so I reasoned the two are not likely to interfere. What did interfere the most was a Chromecast2 on Guest Mode sitting a few feet away from a wireless Sonos device, that was the root cause of my problem, but I did find lots of interesting things going on in the 2.4 GHz band in my environment which includes lots of neighbors (dozens) and xfinitywifi now blasting my house with 2.4 Ghz signals.

Simply changing the Sonos to a different channel may not work in a busy, dynamic environment on the 2.4 GHz band - in my case it made things worse. I had to use a wifi scanner to find the root cause of my dropout problem (Chromecast2), move as many components as possible on my home wifi to 5 GHz, then found a 2.4 GHz channel for my home wifi that was least trafficked, then studied how the outside wifi's responded after I set it to the new channel. I then observed the channel signals after they adjusted, then I set the Sonos to the least trafficked channel.

Dropouts are now quite rare for me and much less frequent than before.
I wish I could edit, but channel 2 wasn't a good choice after all for home wifi despite what the analyzer was indicating. Channel 2 is still going to impact the Sonos on channel 6 despite being separated, plus it impacts neighboring wifi's much more than channel 1 since channel 2 would interfere with anything set to channel 1 or channel 6. I set home wifi to channel 1, Sonos to 6.