Homemade sub used with Sonus Faber Olympica III

How you connect the JBL to your system? Did you use a separate amp to power the JBL?

Its because your "sub" isn't a sub its just another speaker. Its helping smooth response and I'm sure it is better, just not in a way you are expecting or listening for. 

The frequency response of a speaker is only partly due to the driver. A lot has to do with the cabinet. There are websites and YouTube channels that explain the relationship between cabinet volume and bass response, ported and sealed, and other types of enclosures. Long story short you will be able to modify what you have or build something new and it will be better than what you're doing now but not by a lot. Probably you will be even more disappointed after all that work than you are now.

The speakers you have are pretty fine. Combined with true state of the art bass you will be beside yourself with pleasure. The tried and true way to achieve this is with a DBA. It will cost about $3k. A little more if you buy a Swarm from Audiokinesis, a little less if you DIY, which in that case depends somewhat on the finish quality you want. Mine are genuine rosewood veneer and look like this: https://systems.audiogon.com/systems/8367

The Dayton SA1000 amp is the same one Duke uses in his. Also Tim, noble100, and several of us here who have this or very similar DBA. Read the comments. This will be awesome, tight, articulate and tuneful deep bass that integrates beautifully and perfectly with your speakers. This is totally the way to go. 

Parts Express has subs on sale now, with pre-cut DIY kits that make this as easy as possible and are exactly what I did. You can modify like I did to make some or all of them ported, or just build them sealed. Either way will work fine. 

Good question. I didn't specify that did I. The JBL is connected to the system by 10 AWG speaker cable to the same monoblock that one of the Olympicas is connected to. Since the Olympicas only go down to 30hz and I crossed the JBL over at 45hz, there is very little overlap of frequencies so the overall system impedance is virtually unchanged. 

If you like to know how low the JBL and the Sonus Faber Olympica III can go, connect the JBL to one channel and an Olympica to another channel and play some test tone.

https://www.youtube.com/watch?v=fwrbFj9r10Y

Is this because my homemade sub has a 1st order crossover

No.

and the Olympica IIIs have either a second or fourth order crossover

No.

meaning the sub is approximately 90 degrees out of phase to my main speakers?

No.

And if so, I assume I would essentially “Fix” the siutuation by instead adding a second order network to my subwoofer?

No.

These answers have been impossible to Google!

Yes. And you are asking all the wrong questions anyway. The answers to what you actually need to know are provided above.

Hopefully you all can help shed some light on this one! 

I lit that sucker up with a flood light and laser beam.