Homemade sub used with Sonus Faber Olympica III

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. 

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. 

Erik,

The JBL is connected to the same + and - binding post as one of the SFs.

I did not measure the woofer impedance at 45hz. The woofer itself is 8 ohms impedance wise so I just calculated that. I overlapped by 15 hz to make sure I was covered. I know the design of high end speakers would not use that method, but for now, without the tools needed to test for impedance at 45 HZ, I used my primitive method. As I said, I know the JBL is pumping out lots of low bass because I can see and hear it very easily when it is playing by itself. When I introduce the SFs back into the mix, the bass decreases back to what the SFs normally put out. To test this even further,  I hooked the JBL up to one amp and one of the SFs to the other amp. When I was on the amp with just the JBL, same thing, big bass. When I swept the balance to the middle where both amps/speakers are firing at the same time, the amount of bass is clearly lower. Now, it is not nearly as much of a decrease as it would be if somebody's two front mains were playing and perfectly in phase...and then you swapped the polarity of one speaker. It is just...less. And then when playing music with the JBL and the SF, and I swapped it over to the SF only, bass that is about the same as when the balance was in the middle. I then swapped the polarity of the JBL and tried it all again. Pretty much the same result but SLIGHTLY better. And I say slightly as if the JBL is 82 degrees out of phase in one direction and then 98 degrees in the other direction. It really just seems as though I add a capacitor in parallel with the driver upstream of the inductor to make this a 2nd order crossover which would change my phase by approximately 90 degrees. Meaning about -8 and +8 degrees out of phase instead of 82 and 98 when polarity is flipped.

I did it! I added the caps into the circuit changing this 1st order 45hz to a 2nd order 57hz XO. And that was indeed the problem. The JBLs add SO much low bass to the system. And there is no integration necessary as they are crossed over very low so they are just picking up the lowest frequencies the Olympica IIIs are a little lean on AND they are being driven from the same monoblocks the main speakers are. Instead of resorting to a subwoofer that is amplified with a class D, $300 amplifier with a damping factor close to 40, I have a set of Classe' class A monoblocks with a damping factor of 5000 which were $10,000, 8 years ago. What a DIFFERENCE! As long as somebody has 300 watts RMS of good quality power to give their passive subs, I would TOTALLY recommend this method. Huge 1500 watt amplified subs have incredible impact by all means but it is by NO means musical and accurate compared to passive subwoofers being driven by the same amp the mains are. My impedance at the amp's speaker terminals was 8.1 ohms with just the Olympics IIIs and now it is 7.89 ohms. I double checked with a Classe' engineer to see if that'd be a problem long term, and before he answered, he gave an involuntary quick chuckle before he answered confidently, "That won't be a problem at all." Well...that's it. I never thought a passive sub would be such a great addition to a system. I did now switch both JBL crossovers to a 2nd order filter so I have 2 passive subs on this system now.