Subwoofer insight.

Just watched that entire lecture.  Wasn't sure if that was Earl Geddes' theory or @ millercarbon's theory?  If I have to get a microphone and other equipment to start measuring all of this then I am in trouble. Are there any professionals out there who can be hired whom specialize in this? Not asking specifically for my area but in general.  Just like I do something specific for a fee, does this service exist? 
I believe this guy offers this service and is reputed to be very very good

Barry Ober aka the “The Sound Doctor”

https://www.soundoctor.com/whitepapers/subs.htm

I think some people in this hobby like to fancy themselves as engineers.  They get off on over analyzing everything in their systems.  Doesn’t matter really what it sounds like....they just love trying to control parameters to achieve a pre determined outcome.  For me, my ears are my guide and sometimes a tape measure.  Infrequently I may also consult the owner’s manual!

ieales, thanx for your input. IMHO Neutrik connectors s--k. The plastic used is the cheapest crap they could find. It melts if you hold the soldering iron on the pin too long. A good tech won't make this mistake but still. IMHO the best connectors for home system speaker cables are soldered on spade lugs or pins. 
I forgot about the input capacitor trick. The old Dahlquist DQ-LP1 used this trick. They gave you a fist full of capacitors. You picked the right ones based on your amps input impedance then matched the low pass filter with the dial on the front. I managed to get a pair of RH Labs woofers sounding pretty good with it. Now with digital bass management it is a different world. 
Residential subwoofers in general are pretty bad. Most of them have an enclosure designed to be a musical instrument. A proper subwoofer enclosure has to be very heavy and extremely stiff. Put your hand on the sub while playing at 95 dB. That vibration you feel is distortion. With an ideal sub you would feel nothing. This is a very expensive proposition. 
Not using a high pass filter is just a cheap solution used to pull more people in. I personally would never use subwoofers without a complete two way crossover. You can never match up a sub without one. With a 2 way crossover you at least have a chance. With digital bass/room control you can do it perfectly very time. Unfortunately a large proportion of the audiophile community is digital phobic. 

Unfortunately a large proportion of the audiophile community is digital phobic.

also engineering phobic

@rgmd11

You do not need measuring equipment to set up a subwoofer. Measuring equipment would make the process easier and more precise but you can do it by ear and trial and error. Specially with multiple subs.

Barry Ober aka the “The Sound Doctor”

Barry knows his stuff but he has a different approach. He is a very big proponent of active crossovers. If you are from the school of any extra electronics in the signal path is bad, his method may not be for you. If you subscribe to the thought that a crossover is just another tool in the toolbox and if used properly it can enhance your systems sound, then maybe his approach is for you.

Either way his test/setup CD is probably a worthwhile purchase.