Homemade sub used with Sonus Faber Olympica III

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

How, exactly did you wire the subs to your amp and main speakers??

Of course, one good measure is to put you hand on the sub and see if things are moving. :)

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.