Separate subs for music and HT/surround

     Just as I suspected, you had no legitimate purpose or reason for including and misconstruing millercarbon's prior post.  Thanks for confirming this.

Tim

OmniMic or REW are more accurate Measuring devices. Promoting anything other than measuring with instruments is misguided advice. 
While multiple subwoofers are accurate advice, and provides enduser with a smoother response at the LP, this is 2019 and we have software and hardware that are affordable and accurate.

a comprehensive multiple subwoofer array setup scheme combined with proper calibration equipment will get you much closer than archaic “crawl” method.

If crawling around was a conclusive method, Kef and Velodyne would scrap their testing facility and hire professional “Crawlers” :0)

Kg

Actually, on page 25 of the Velodyne Digital Drive Plus User’s Manual under the heading of Optimize for Subwoofer Placement, "you place in the room according to the information in the general section and optionally the "Crawl Test" section in the Subwoofer Placement Recommendation Guide" (where the "Crawl Test" is explained in more detail).
As a multiple DD Plus user I can confirm that DD Plus Room Optimization can compensate for time and phase issues that may arise from less than optimal positioning. Its ability in dealing with any rooms unique modes and nulls is far less effective, if at all, compared to beginning with the suggested "Crawl Test".
Sadly, the Velodyne facility is now used for Velodyne LiDAR.

No wonder SVS is climbing toward the top in subwoofer sales, design, R&D

if i read SVS recommends crawling around rather than a $60 mic and free software and a lsptop, i’ll throw in the towel Lol

   The SVS Ultra appears to be the first affordable subwoofer with an application that offers needed low frequency crossover related adjustments as well as three customizable memory EQ presets within a single frequency band between 20 and 200Hz.
   Velodyne, JL Audio, Vandersteen, Magico, and Von Schweikert, understand the importance of multiple frequency bands of discreet equalization within a higher crossover region without reducing gain and not simply a set point where the subs kick in.
   SVS claims (SB16-Ultra Owners Manual page 15), "in some cases, reversing polarity - can be used to fix bass nulls or overly boomy spots in the listening area". While it may have a minor affect reversing polarity simply restores the polarity of the recording which is most noticeable in the bass drum and can vary as often as from track to track. If the listening position is located within a null or mode the sub will require proper physical relocation. With the sub at the listening position you don't actually need to crawl around to locate a rooms modes.  
   I'd venture subwoofer sales are related to affordability rather than flexible frequency integration. If they've never heard it how would they know what to listen for? After all, almost any sub sounds better than no sub.