Separate subs for music and HT/surround

db, were you able to get your subs repaired?   
   I think the SMS-1 has some memory presets that will allow you to EQ one unit for both stereo and HT. There are two manuals for your SMS-1 the Velodyne and the Outlaw. http://velodyneacoustics.com/product-manuals
   My DSP experience begins with the Digital Drive 18" and my current two DD-12 Plus. You should gain some insight by looking up both Velodyne's DD Plus User's Manual for multi sub connectivity pages 16-20 and the User Interface Manual. 
   You'll notice the subsequent additions to their software most notable the Frequency Response and Parameters Screen on page 10 of the Interface Manual. Following the Auto EQ program this one feature allows you to click on a frequency band diamond and manually make three adjustments siamotainously within that one band. 
   This adjustment allows you to closely duplicate the Q and filter the subs to closely match your main speakers presentation from 200Hz to within the crossover region. Beginning at 100Hz this adjustment can be feathered long before the main speakers low frequency begins to drop off. After some listening to music there will be some tweaking to taste. Opposed to a sub simply coming on at a set frequency this result is like braiding the subwoofers to the mains and literally defines seamless integration.
   After this adjustment I have four memory presets with slightly different gain settings. Take the time and get comfortable with the SMS-1 the rewards are worth the effort.

   When I purchased the DD Plus' in 2012 I still had the DD-18 and an EarthQuake Nova 15. Before equalization I ran all four subs and experienced the room loading and the lack of any modes. Using one 12 as a master and running Optimization and Parameters the results were greatly improved. I removed the Nova followed by the DD-18 with no sonic degradation but gained a mode deep in one unused corner of the room. 
   In my limited experience proper sub placement and this level of optimization far exceeds the need for four subwoofers in the two rooms I've used this system in. The variability between extra low frequency systems, rooms, and personal taste is so great I'm guessing there are very few absolutes. Good luck with it.           

Thanks for the information and suggestions, m-db.  The repaired subs should be installed Tuesday.  Using the equalized output from the SMS-1 during the setup process revealed the in-room acoustic response of the KEF Ref 1s in the 15-200 Hz region before I unmuted the subs, an unexpected benefit.  I'll try to dig more deeply into the SMS-1.

db

db, I forgot to mention Velodyne Acoustics may have suspended their audio related production due to successes with Velodyne LiDAR.  

Keep a list of any third party service providers and print any pertinent manual and wiring information from the site I linked in my previous post. Under Service the site lists two service providers. One on the east coast the other in the LA area. They may be the only access to actual product wiring diagrams.   

I used George Meyer on Jefferson Blvd in the Baldwin Hills area of LA.  The cost seems reasonable.

Good. Being in California they may be the best knowledge source going forward.

I found a contact in Los Banos who seems to discounting their remaining new stock which seems to be located in Fremont CA.