Thought his group might be interested in my adventure adding four additional subs, three powered non Sonos subs and couch bass shakers to my Sonos sub. The Sonos sub is paired to a Sonos ARC and two more One SL’s for a 5.1 system on the TV. I had but shakers in the couch and several other subs left over from the conversion from a Pioneer Elite system. Got tired of having to update the receiver for the newest audio formats, 3D, and 4k. Then the hardware 4k bug hit the latest crop of AV receivers and I pulled the trigger on the Sonos ARC and sub. The sound quality was not quite the same but the versatility and ease of use of the system is easily makes up for it especially if you ask the wife. This mod took the sound quality up to be nearly equal if not better.  

I wanted to use my existing non Sonos subs but did not like the mods I found on the interwebs connecting powered subs to Ones and Plays directly from the speaker outputs. If I did that I would have no real processed sub audio from the Sonos  ARC and app. I thought about investing in another Sonos sub but spending another $800 did not seem the answer and I would not get the bass shakers in the couch going again. I decided to tear apart my shiny brand new Sonos sub and connect to its speaker outputs and drive my existing power subs and bass shakers through a speaker level to line level converter. 

I thank the guy on YouTube who posted a video on how to open the Sonos Sub. Without his repairing his broken Sonos sub I would not know how to open my sub without damage. I avoided the damage to the trim ring held firmly on with double sided tape by using a blow dryer to heat it up before the delicate prying off. 

Once the trim ring is off the screws are exposed and the opening can truly commence. I added four banana jacks to the bottom recess on the Sonos sub. I connected them to the two speakers inside the sub. The Sonos sub is a high quality built sub. Sonos used great technique and engineering in the sub. The main enclosure seems to be fiberglass or fiber reinforced resin. 

I used an external, quality, powered, two channel speaker level to line level convertor made for bass. from there I send the line level through my existing wiring to my three other subs and couch bass shakers. After a little tuning the sound is dramatically improved. The couch seats and house rumble during the right times during a movie and I can control the sub level level via conveniently the Sonos app. The Sonos sub still provides good bass and remains unaffected if pull the banana plugs out. Most normal folks would not notice the mod on the bottom. 

Now I have this dumb thought of opening the Sonos ARC to access to the up firing ceiling speakers to improve ATMOS. Ok someone, please tear open your ARC and post on YouTube

Oh and by the way, I just found out my Nvidia Shield converts DTS audio encoded movies  to 5.1 Dolby to play on my ARC. 

inside of Sonos sub with cover off

inside Sonos sub with banana jack mod

exterior of Sonos sub with banana jack mod

inside Sonos sub with additional speaker connection.