Sonos Amp and 3rd party subwoofer issue

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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.


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 

I can confirm this as well - the latest update to version 11.1 seems to have solved the sub output level problem with the Amp. I’m not sure why this went unacknowledged so long, nor do I understand why the fix went out so quietly. Regardless, the Amp now seems to be functioning up to the high standards of the other Sonos devices. A big thank you to whomever was able to identify and resolve the software issue!

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.

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)

Same issue here - weak signal from the Sonos Amp’s subwoofer output makes it basically useless. I have to set the Sonos Amp to +15 and turn the sub’s amp all the way up to get audible sound from the sub. When I use this exact same sub setup with other sources it literally shakes the house with the sub level at 1/4. There are lots of threads and discussions about this; I find it infuriating that Sonos won’t at least acknowledge the issue. It’s also disappointing the product has such an obvious flaw when all the other Sonos stuff I’ve had has been quite good. I really wish I had come across these discussions before I purchased the Amp so I could have avoided it.

Same issue here, quite pissed off because I paid a lot of money to integrate my HT to Sonos. No bass at all. Don’t know what to do.

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.

I had the same problem when I got my amp and connected my subwoofer with a simple rca cable: the sub output was very low and I had to crank up the sub level in the Sonos app. Everything was fine after I switched to a y-cable (1-male to 2-male), now connecting both (L+R) inputs of my sub. These cables are available for around $10. Maybe worth a try...

Even if this works, it will involve clunky workarounds. Why bother? Why not just get a Sonos Sub?

True, but was hoping to save $100 and use my more powerful subwoofer (svs ultra). Having one less bulky device in my house would also make it easier with wife approval 😛

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? 

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?

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I am glad I found this post about the sub issues. I can’t believe someone posted if you buy MCM Stereo LINE PRE-Amplifier, 15DB, 12VDC” it will resolve your issue. That’s like if you change your Tv you might get better audio out support.  For such premium price products  doesn’t  this stuff get tested before it is out the door.  All those high end artist that they advertise must have had the issue, wouldn’t you think.  Since it is a system depended on wires I don’t understand why people don’t use a new traditional amp. Amps today can connect to many different steaming platforms including airplay/2 without these types of issues/frustrations. They connect with alexa or google and some even allow power control from those. Better yet Nov /Dec is the time to look at buying those at a fraction of the cost. Yet another sonos product that I won’t buy and that makes this very disappointing again. QOS turns out to POS. As a consumer do we really ask for that much? 

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……..

Badge +1

Hi everyone, thanks for sharing your experiences with different devices and the Sonos Amp. We’re always interested in seeing what you have to say, and are eager to investigate any issues that might come up. Our engineering team has been looking into this issue and would love some more information. Currently, there isn't a major trend that has been identified, but they'd like to see some more cases where subwoofers and the Amp aren’t behaving as expected. 

If you’re having trouble with the Amp outputting low or no audio to a subwoofer and haven’t worked with our support team yet, please feel free to reach out to us using the contact details here. The support team will help sort out issues where possible, and if needed, they’ll gather the right information and get it up to the engineering teams for investigation.


Hi Ryan and others,


I have been following this thread with interest.

I have replaced an old Onkyo amp and Sonos Connect, running an Onkyo SKW-501 active Subwoofer with the new Sonos Amp. 

Similar to others I have to have my subwoofer output set to +15 to get a reasonable signal. This in itself is not a problem the majority of the time.

The thing that IS annoying is that the Amp does not trigger the subwoofer to wake from standby whenever it is active. For example I am currently watching the News on TV and the subwoofer is in standby mode. When a bass note plays the subwoofer will kick in but usually with a ~1s delay which is noticeable. When watching a Film/playing a Game this is rarely an issue as there are enough bass notes that the subwoofer wakes from standby and stays on, otherwise after about 15 minutes it returns to standby. There is unfortunately no switch to disable standby mode on the subwoofer. The Onkyo FAQ recommends increasing the output from the Amp, but unfortunately as already at +15 this is not possible. When the sub was running from the Onkyo amp, the second the amp turned on the sub would come on and stay on.


Clearly this is an issue with the Sonos amp outputting a very low subwoofer pre-out signal.


I spoke to Enos at Customer Support and submitted a diagnostic (403792976). I referenced this article. He could not see a fault with the Amp and suggested this was an issue with the Onkyo Sub standby circuitry being “overly sensitive”. Although this may be true, it’s clearly not an ideal situation, and although the plan will be to upgrade the sub in the future that is not feasible right now (the Amp is expensive!). 

He did say he would pass my experience onto your Engineers.


Hopefully if enough people report such an issue a solution will be found.






Following responses as well.

For anyone that wants to remedy this major flaw in the AMP, you can go to amazon and search for “MCM Stereo LINE PRE-Amplifier, 15DB, 12VDC” and add that unit between your 3rd party sub and your AMP’s sub output. There’s no need for Y cables when using this with a mono (single RCA) connection, as you are able to use just use one side of the pre-amp.

Badge +2

You really have to question quality of product and why any of the professionals they use in advertising ( which makes users believe they are active users and listeners)  did not pick up on this issue up. You decide on why, I won’t say what I think.



Are you using the line-level connection?

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So is bass still set to 15 GDaz?

What brand and model of sub is everyone using and how do you like it? How low can your sub go?

I currently have 4 Sonos Amps that I’ve being using for the past 2 months with out any subs. Yesterday I got my SVS Ultra PB16 and for a good 3 hours I couldn’t get it to work, I thought I had a defective Sub, but after being on the phone with SVS support and messing with the Sonos App we came to the conclusion that the signal is way too weak, I was able to get a bit of base by cracking the level to +15 and setting the Sub to Max volume, which it sucks. We actually tested the sub with my Ipad by using RCA to Headphone Jack in the Ipad and its sounds amazing so this confirms the sub is fine. Unfortunately I can’t return my Amps and I dont want to return my sub, so what Im thinking of doing is buying a Yamaha receiver to power my In-ceiling speakers and sub for a true Surround system and control it with a Sonos Port.

Oh and by the way, if You have a Sonos Sound Bar and you want to create a 7.1 system, it wont let you, this is another reason as to why Im considering getting a Yamaha Receiver since Sonos is not all there yet.

Userlevel 2

Given that this issue is so easy to reproduce It is very frustrating that Sonos has yet to resolve (or even acknowledge it). 



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.👍