Sonos Amp and 3rd party subwoofer issue

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I am having issues connecting my Sonos Amp (Black) to my Klipsch SW-311 10-Inch Subwoofer (or vice-versa). I currently have two Klipsch speakers and the Klipsch Subwoofer connected to the Sonos Amp. Both speakers play but I am getting no sound from the subwoofer. The subwoofer is connected to the sub port on the Sonos Amp and the LFE port on the sub. The sub plays when connected to my Yamaha system but doesn't play when connected to the Sonos Amp.

Is my sub's connection wrong? Will a sub with a built-in amp not work with the Sonos Amp? What am I doing wrong?

Help please...


121 replies

Following responses as well.

Userlevel 7
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Why the Y cable?

A simple male-male RCA is all that should be needed.

If you connect another audio source to the external amp’s input using your cable can you hear anything?


I’m Exhausted. Searched the web for hours. Read this thread 2 times. 

I have a Sonos Amp. Trying to use the SUB out on it. Yes, it has the latest firmware.

Brand: OSD Audio Model Name: FORZA 10 Sub running thru an external Amp. Using an RCA Y cable from Sonos Amp Sub out to the line in on the Amp. Zero on the Sub. I do get the Sub enable/settings once I plug in the RCA but thats it. Useless.

Other than buying a Sonos Sub, What Amp works with this. The external AMP for this Sub is Nobsound G2 PRO Hi-Fi 300W Subwoofer Power Amplifier Mono Channel Class D SUB Audio Amp. 

But like so many others here, struggling to get this to work. 

Any help is greatly appreciated.

Very glad I found this thread.  We have (4) Episode rock speakers in our back yard around our pool, and two Def Tech AW6500 under the porch aimed at the pool...all setup on Sonos.  I was looking for a cost effective way to add more bass back there and was going to wire up a Klipsch 12” sub under the covered deck, that I would likely move inside when we weren’t out there using it so that it wouldn’t be subjected to temp changes and humidity.  Sounds as if I may waste a lot of money doing so.


Can anyone else confirm that high quality, shielded sub cables and Y adapters solved the issue?  Thanks!

I am having the same issue with my infinity subwoofer.

Me too.. with Polk Audio Outdoor Subwoofer :(

I use a Sonos Amp connected via Line-In to my computer. I’m using Definitive Technology bookshelf speakers (ProMonitor 800s) and a matching Definitive Sub. I have been having the same issues - no sub output from the Sonos Amp. I tired several things, including unplugging/plugging in the sub along with trying different outlets in the room. Ultimately, what WORKED is setting the volume level in the Sonos App on the Line-In output (my Amp) above 50. Then I adjusted the volume on my computer to suit. This kicks the sub on … perhaps because there’s more “power” coming from the Amp. I have experienced this before with subs that have power, but an auto switch (no native on/off manual switch). Try it if you’re having issues. It worked for me, and it kind of makes sense. You have to force the sub to kick on, and the best way to do this is from the Amp itself, through the App. PLease let me know if this works for you as well. I would be interested to see if this is a widely acceptable solution. 

Hello, folks. I am new here. I have used Sonos equipment for many years. I am replying because I had this same issue with the very same Klipsch subwoofer. I solved it, so I wanted to share. I think, but I am no expert, that the LFE output is set up for a 5.1 system. I am just running a 2.1 system. Nothing seemed to work with the cables I was using, and I had lots of buzziness from interference. The fix turned out to be very easy. I ordered decent but not obscenely priced Y cables which were insulated, plugged them in, and, boom, the sub was up and running, and, wow, this is a powerful set up. For my apartment, the sub verges on too much, and it is probably rattling the ceiling of the unit below. But all I needed was a set of Y cables, from Amazon, and I’m all set.

So with all these issues I think the best solution is using your 3rd party subwoofer without the use of the sub port.

Connect the amp to the subwoofer via the speaker output to the subwoofer speaker input.

Then connect your speakers to your subwoofer via speaker output

This is used for amps without the subwoofer output possibility.

Any cons for this configuration? This shoud work IMHO for 2.1 and 4.1 So the fronts are connected to the subwoofer and the sub WILL work With wireless sonos surround speakers. IAm I missing something (considering to the ones whoa have speaker input AND speaker output on their subwoofer)


Maybe there’s a fault - you could try connecting it at the speaker-level instead, as stated in its user-manual, or try a different cable - if no luck, then perhaps contact Sonos Support Staff via this LINK

Hope you manage to get it sorted.👍



Are you using the line-level connection?


Same problem as everyone else. Amp powers Polk speakers fine. Doesn’t do anything to a reliable and functional Bowers/Wilkins active sub. How do I fix this? 

Which B&W Sub is it?

Same problem as everyone else. Amp powers Polk speakers fine. Doesn’t do anything to a reliable and functional Bowers/Wilkins active sub. How do I fix this? 

Ordered a Sonos Amp two weeks ago, because my Connect:Amp broke down. 

I’m having a Cambridge Audio Minx X300 subwoofer that works perfectly fine with other systems but not with the Sonos Amp. 

I got it to work two times but it suddenly stopped working after a couple of hours, after both of the times. Now I can’t get it to work again. I have contacted the Sonos support and sent them a couple of diagnostics and they ask me the standard questions, like, “Is the cable connected?”, “Have you tried a different cable?”, “Have you set the Subwoofer to be Forced. ON?” etc. and I have tried all that they have asked, but sadly it wont work. 

So final verdict, I’m returning this miserably failed product.

It’s a shame that they happen’t been able solve this issue since 2019. 

So take my advice, don’t buy the Sonos Amp if you have a 3:rd party subwoofer.

Hey there, jale01. While attempting to play audio to the Klipsch subwoofer, please submit a diagnostic report and reply here with the confirmation number. I'll be happy to take a closer look and point you in the right direction. The Sub Out of the back of the Amp is line level so it should work with no problem when plugged into the LFE port.

My Sonos amp subwoofer audio crashes the app when I click to adjust the subs audio settings. Android 12. Note 10+ 5G

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My issue turned out to be with the subwoofer’s amplifier. All working now, except that at times I do need to turn the volume higher than I intend to listen at in order to wake up the sub. Really wish the Amp had a 12v trigger.

I am experiencing the same issue. The Amp will not wake the sub up after going on standby mode. Using KEF KC62 which I just bought……..

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Is anyone still experiencing any of these issues after the update? I have a Polk HTS-10 connected to the Amp through the sub out RCA  output. It sounds great when the sub is first powered up; none of the volume issues that were initially reported in this thread. Once the sub goes into standby mode though, the Amp will not wake it up, even if I increase the volume to uncomfortable levels (50% or more). In the settings for the Amp I can see that it still senses a sub is attached. I can only get the sub working again by unplugging it from power and plugging back in. This happens with both the LFE input and R/L low-level inputs on the sub. It does not have high-level inputs and does not have an “always on” option, just auto detect or 12v trigger.


I’ve tested the sub with other components and they all wake it immediately from standby with no issues.

Userlevel 7
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In your own thread the explanation for this is given by Melvimbe:

“I believe he wants the sub port on the amp enabled while the amp is in surround mode, so that he can use a 3rd party sub.

I don’t think you can conclude it’s an easy change, only disabled for marketing reasons though.  As it stands now the Arc/Beam is currently configured with or without a Sonos sub.  If no sub, then it plays the bass frequencies itself.  With sub, it sends bass to the sub and adjust it’s own speakers to no longer play those frequencies.  Now you’re talking about a 3rd scenario where the Arc/Beam needs to be told that the amp for surrounds has a sub attached to it, so it should adjust it’s on playback accordingly and send the L/R surround channels AND sub channel to the amp wirelessly.  Not sure that the amp is built to handle 3 channels of audio like that over wireless, and process it accordingly.  Maybe, but I certainly couldn’t conclude that it’s a trivial matter. 

Note, this is not the same as when a amp w/sub attached is playing music in a group situation.  The amp would receive the 2 stereo channels and extract the bass from that.  It can’t do that when it’s doing surround duty as the bass is a part of the front channels, not rear surround channels.”


Sonos Amp Feature Request | Sonos Community



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System posted twice.

The only way to connect your 3rd part SUB is to configure your Amp in a separate room to your Arc or centre speaker, if you add the AMP to the same room setup as your Arc then the output is disabled.

This is a bad marketing move and just a money grab to get you to not use your existing Sub and to purchase the Sonos SUB…

If you configure your Amp in a sperate room and add your L + R speaker and Sub they work, but when you put them all in the same physical room as your centre speaker the sound is out of phase and it sounds bad

Thanks...kind of disappointing that it has the inputs on the amp but they all can’t be used 

I guess there are perhaps technical reasons why the Amp ports are disabled as the Amp just becomes a slave to the Arc master device. If the Amp is set as the HT master device for the front channels (in place of the Arc) then all the ports are not disabled and the 3rd party Sub can be used in that kind of setup, just not when an Amp is used for the rear surrounds.


When the Sonos Amp is used for HT rear Surrounds all the Amp ports, including the .LFE Sub port, are disabled. So a 3rd party active Sub can’t be used with that type of setup, you can only use a Sonos Sub when a Sonos Arc is being used for the HT front channels.

Thanks...kind of disappointing that it has the inputs on the amp but they all can’t be used 


When the Sonos Amp is used for HT rear Surrounds all the Amp ports, including the .LFE Sub port, are disabled. So a 3rd party active Sub can’t be used with that type of setup, you can only use a Sonos Sub when a Sonos Arc is being used for the HT front channels.