Rather than waiting for a forum moderator to pick this up, you may want to call Sonos Support directly to discuss it.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

Although if it’s not a failure with the Sub or the Sonos device that feeds it directly, but instead a signal being passed to the Sonos system, it may be hard for them to figure out. 

Ok, thank you. In fact I already had in mind to contact them by telephone.  I was just curious if any other users noticed this.  I have read the forums of several people who have “pop” when turning on the system, but I have not found any cases of “pop” at the end.

A faint pop a couple of minutes after stopping playback would be normal, at the point when the amplifiers shut down.

Thanks, ratty, I think so too.  In my previous and long experience with the old analog systems, this type of sound was quite frequent.  But the Sonos world is quite new to me and I was a little worried, having invested a fair amount ...

I’ve received my first Sub (Gen 3, A202 build) in the past few days, now paired with two Sonos Ones (Gen 2). I also noticed the single soft pop sound when the Sub becomes active from standby and thought the sound was a bit odd because I previously never heard any startup sounds/pop sounds from my stereo Sonos One’s without Sub. I hear a similar single soft pop about two minutes after the music is stopped and the Sub goes into standby. Overall sound quality of the Sub that I have is good, aside from this pop point.

I’m not an expert in amplifiers but from reading other audio forums online, I’ve seen it mentioned that modern, premium amplifiers often have a soft-start feature to prevent the pop sound when they are being powered up. This makes me wonder have corners been cut in the Sonos Sub resulting in the pop sound, or is there a technical reason why this particular subwoofer amplifier design has to have a pop sound when becoming active? I’ve also read in this Sonos forum that other people are not hearing any startup pop from their Sub so I’m wondering if certain batches of the Sub have cheaper components without the soft-start feature, which results in the pop.

These are ‘perhaps’ questions you might want ask of Sonos Support Staff. I’m not sure anyone can comment on different batches of Sub and/or different components, plus if you are concerned by the sound and are able to capture the issue with a video/audio recording and/or submit a system diagnostic report (noting it’s reference), then I guess the Staff should then be able to comment further on the issue and say if your Sub is working ‘as designed’.

Here is a link if you do wish to take the matter further and to speak with them:

https://support.sonos.com/s/contact

Hope that assists.

Thanks @Ken_Griffiths  I called Sonos Support and they had a look at the diagnostic for my Sub and Support said it needed to be replaced. The replacement is on route to me now, I will provide a further update when the replacement is received. 

Hi all, to update on my previous post, I received the replacement Sub unit, while I still also had the original Sub unit at my location, and I listened to both carefully side by side - both Subs had the same behaviour of making a soft pop sound when coming off standby, then another soft pop after 2 minutes if the music is stopped and the units go into standby. I could hear the pop sound from across the room approx.10 feet way on both units.  I also noticed if I put my ear right beside amplifier on both units with the music stopped that I could hear a sort of electrical static or whirring sound occasionally, but this was only audible if I put ear right beside the amplifier. 

Manufacturing dates and build of the units for reference:

Original unit: Sub Gen 3, build A202, manufacture date of May 2022

Replacement unit: Sub Gen 3, build A202, manufacture date of February 2022.

I still wasn’t happy with the pop sound behaviour on the two Sub units, so I then spent about 3 hours on a call with Sonos Support trying to get a clear answer on whether the pop was expected behaviour and if there was any point in getting another replacement unit. At first I could not get a straight answer on expected behaviour of the Sub sound, but eventually I got through to a knowledgeable Sonos technical engineer who advised that Sonos’ own design for the Sub Gen 3 is not intended to make any pop sound from standby, but due to ongoing manufacturing/supply chain issues the Gen 3 is still having these types issues, and that most likely if I got another replacement unit I would hear the same issue.

I have therefore decided to return the original and replacement Sub Gen 3 units for a refund as I’m not willing to compromise on the sound quality given the Sub’s high price point. I might consider buying again next year when the electronic component shortages caused by the pandemic have improved. 

Another observation from my side is that the replacement unit had minor cosmetic damage (scratches) on the back panel of the Sub, as if the panel was previously pried open with some sort of tool, so I suspect the replacement unit was actually a refurbished unit, even though there was nothing marked on the box that it was a refurb unit. The original unit had no cosmetic marks/scratches like these. If the replacement unit was indeed a refurbished unit, it is disappointing that Sonos is supplying refurbished unit to a customer who has paid the price of a new item.  I don’t intend using the Sonos replacement service in future. 

Did you every purchase the sonos sub again? Im experiencing the same thing with my sub. I first got a replacement sub because my last made a static noise and the new replacement is also making a static noise plus the pop sound when going back to standby after two minutes. 

No, I haven’t purchased a new Sub since I received my previous refund, I was giving it a bit more time for component shortages to be less of an issue. This is disappointing to hear that you are hearing the same issue I was experiencing in 2022, I was hoping the issue would have been resolved by now if the issue was supply chain/component shortage related. Can you see the manufacture date on the label on your unit to see how recently your unit was made? The label should say something like A202,  then month and year of manufacture. 

My unit was made in October 2022. Have been in contact with the support and tried to record the pop sound, but I wasn’t able to pick up the sound with my phone even though I can hear it from 3 meters away.

OK, that was manufactured later than the unit I received (mine was manufactured May 2022), so the issue must still be affecting newer units, which I find odd these issues haven’t been resolved in newer units by now. If you are not willing to live with the issue, I would recommend to return for a refund if you are still inside the return window. I expect there won’t be anything that Sonos support will be able to do to fix the issue if it’s hardware related.

I see Sonos has recently increased the price of Sub Gen 3 again to 899 Euros in Ireland  Not great to see price increases when there are clearly ongoing quality issues.