BillFitzmaurice.info

Hi everyone.
I need some help trying to figure this out!! when comparing/testing my sub against my friends , i was testing his rcf esw1018 and found something very strange.
i will post graphs from smaart tomorrow , however here is what happens. the cab has a low pass filter switch . when you flip it to the (on) position, you get a massive spike in sensitivity from 60-90hz range. w slightly less output below around 55hz (1-2db less) what is the magic? im seeing almost a 6-8db boost from this mysterious switch in the 60-80 range testing w smaart and pink noise
I believe bills cabs may be able to benefit from whatever this passive circuit is existentially in the 60-80 kick range.
it has blown my mind and confused me very much.

Were you testing with the mains playing? If so I would guess the mains and subs were out of phase and the phase shift of the crossover brought them in phase when you flipped that switch.

Magic is science that we don't understand yet. Whatever that switch does it would be easily figured out with a schematic of the circuit.

so the sub was tested alone (no tops) in a open field, with no processing at all was applied.

Bill, I don't have a schematic or a way to get one, but have you ever heard of such gains from something passive in line with the woofer?
I can't understand it cause I always figured hard wired to the woofer would yield the most output per voltage applied...

nick mineau wrote: ↑Wed Jan 23, 2019 1:31 pm so the sub was tested alone (no tops) in a open field, with no processing at all was applied.

Bill, I don't have a schematic or a way to get one, but have you ever heard of such gains from something passive in line with the woofer?
I can't understand it cause I always figured hard wired to the woofer would yield the most output per voltage applied...

An elliptic or chebyshev passive filter lowers the impedance at/near the x-over frequency. This increases the current, hence power. For a given voltage that will increase the output.

CoronaOperator ,
I have never heard off that. very interesting stuff tho. it does say 80hz on the switch so maybe that's why i'm getting that bump in that range.
seems logical to me. the bump in sensitivity caught me off guard. I guess there's no free lunch...
Ill bet the impendence curve (which I don't have) set and tested both ways would tell me a story

CoronaOperator wrote: ↑Wed Jan 23, 2019 1:38 pm An elliptic or chebyshev passive filter lowers the impedance at/near the x-over frequency. This increases the current, hence power. For a given voltage that will increase the output.

It also can lower the impedance load to where the amp can overheat. I've experimented a lot with high Q filters, and they can give a lot higher sensitivity, enough to give you a woody.
Then you run an impedance sweep and see that you're down to 1 ohm and reconsider.

so based on what your saying bill its not worth it because though the sensitivity at a given voltage goes up, its not adding power efficiency, its just artificially loading the amp.
and the speaker is still dissipating that added current, as if you just used a larger amp in the first place... NO FREE LUNCH>>>


i do wonder tho, cause i like to tinker... is there a simple (high Q filter) I could buy to stick in line w a sub just to see/hear it in action on a diy cab.
id like to show my friend how its not magic lol

Download and play around with this crossover simulator: http://libinst.com/Xsim/XSimSetup.exe

Here I made a simple 2nd order x-over with a 6db bump around 70hz just by playing around with the inductor and capacitor values, impedance goes down to about 1.5 ohms:



click on the image then on the +magnifing glass top right to blow the image up.

You would need one of these: https://www.parts-express.com/erse-supe ... l--266-934
...and one of these: https://www.parts-express.com/500uf-100 ... r--027-378

That should give you a nice bump on an 8ohm speaker ... if your amp can handle the low impedance without going into protection.

Wow! The knowledge shared on this form is so helpful! I can’t tell you how appreciative I am for the help ! Thanks