Homemade sub used with Sonus Faber Olympica III

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. 

Millercarbon, you say it isn't a sub and that it is just another speaker, I want to make sure I'm not missing something here. The famed 128H woofer used in the JBL L150A speaker is still in the original speaker box where nothing has changed other than me disconnecting the mid and tweet, completely bypassing the factory woofer crossover and then adding a first order low pass crossover to the woofer. The 12" woofer with the 12" passive radiator in the factory 5 cubic foot massive box finds the -6db at 20hz with these speakers so they definitely go lower than most subwoofers on the market. If I disconnect my Sonus Fabers main speakers, the Classe' monoblock runs only the single JBL and it puts out so much bass I can clearly feel it in my chest and it fills the entire house with low bass. If I connect the mains back up, the bass sounds great...but just as good as the Sonus Fabers are by themselves. If I disconnect the JBL at that point, there is no noticeable difference in sound level or low bass extension. If I swap polarity on the JBL is also seems to be identical when added to the SFs...a whole bunch of nothing. That is why I was thinking it was my 1st order crossover network that was causing my JBL to be 90 degrees out of phase with my SFs. 

I should also say that the JBL by itself in this situation puts out, lets say on a scale of 0-10 where 10 is the best bass that can be imagined, bass that is a 7. The SFs by themselves is a 5. The SFs AND the JBL together are a 5. So there is a noticeable decrease in bass low extension and bass SPL when all 3 speakers are hooked up at the same time. The decrease in bass low extension and SPL are identical when I switch the polarity on the JBL in this case as well. So that would find the bass being a 5 as well. This just doen't make sense to me. I understand adding a massive sub with a 1000W dedicated amp will add a lot due to sheer power but there should definitely not be a slight reduction in bass when adding another woofer to the system that is being powered with 300W RMS of Classe' power. 

I think your solution is add a high pass filter to the Sonus Fabers or use a separate amp to power the JBL.

Lots going on here, really lots. :)

No way to tell how you calculated the low pass filter.  Did you measure the impedance of the sub at 45 Hz?

My guess is that you may not have the filter set correctly and/or that it is too low.

Best,

E