Hi @Matp 

Welcome to the Sonos Community!

Yes, though you won’t need a 4th Amp - just connect a powered Sub to the Sub connector on one of your Amps.

For the Amp, we recommend using Sonance Architectural speakers, but any 8 Ohm speakers capable of 125 Watts should suffice. Please also see our Set up your Sonos Amp page.

I hope this helps.

I don’t know that I’ve ever seen an outdoor powered sub.  The majority appear to be passive, using speaker wires and a crossover to achieve bass.  In that case, you definitely would need another amp, or an impedance matching switch, at a minimum.

However, I’ve noticed that outdoor passive subs don’t get all that low, around 50 Hz.  A lot of outdoor speakers get that low on their own, including your B&Ws.   That Sonance you picked out gets to 35 hz, so indeed could be a big improvement.  Note though that your B&Ws/amps will not be aware of the presence of the sub and adjust automatically.  One sub also may not feel enough for your space.

Simply adding a subwoofer to one AMP will not likely solve your issue because the other AMP/speakers will still send full bass to their speaker. You could fake things a bit by inserting a dummy RCA plug into the other AMP’s subwoofer port and claim that they also have a subwoofer connected.

Keep in mind that your outside ‘room’ is rather large and will consume bass energy. You may need multiple subwoofers.

I don’t know how easy or hard it will be to run a wire from AMP to an outside powered sub. And, there is the issue of power for the subwoofer. An alternate plan would be to use a 3rd party amplifier for the subwoofer and run speaker wire(s) to passive subwoofer(s). Again, you would need a wire.

Yet another scheme (but not recommended) would be to use passive subwoofer(s) attached to one or more outside speakers, In this case you would need to insert the passive subwoofer(s) into the wires to the smaller speakers. In any case you must block the bass energy to the smaller speakers.

Good point, @melvimbe! I was thinking of technical feasibility rather than market availability. Thanks!

@buzz @melvimbe now I will reveal my ignorance here, but why is i a problem that the b&w’s will not be aware of the sub and keep sending bass? Can I just not adjust the equalizer and minimize bass? It is actually more bass I am after. And I am happy to install 2 subs, wire is not a problem. Anything you can recommend that is better than the Sonance? And why a 3rd party amplifier and not an sonos amp that I can steer in the app together with the rest?

If the Sonos equalizer cuts off bass at exactly the same frequency as your sub takes over, then it would be fine.  You could end up with a gap where neither your main speakers or sub covers a range of frequencies.

Not exactly sure why @buzz is suggesting a 3rd party amp, but it may be because you could get a larger amp than Sonos provides to provide more power to sub(s) without paying for the Sonos ‘smarts’ that you won’t need.  For example, you could have 3 amps, a port, and bigger 3rd party amp for your backyard. Not sure you even need the port, if the 3rd party amp can get a signal from an amp sub output.

For my backyard,  I have 2 pair of Polk Audio Atrium6 a pair of Polk Audio Atrium5, and a pair of RC80is.  (Honestly, I really only needed the Atrium6s)  They are running off of 2 amps and a port  + 3rd party amp.  The last 3rd party amp is really just because I had it lying around, and for a part of the yard I really don’t need it in.  I’ve never felt that I didn’t have enough bass, but I also didn’t expect it to be that ‘bassy’ outside.  Certainly not having any issues at high volume.

I probably like the RC80s the best, not so much because of the speaker but the placement in the ceiling with open space above (attic) and semi enclosed area that seem to help the acoustics.

Yes, running an AMP’s subwoofer output to a 3rd party amplifier would be an overall simpler setup, and likely to be less expensive. This also works around the issue of providing power to an active subwoofer outside. Weatherproof active subwoofers are not common.