I'm trying to create a passive RLC band-stop filter for my Sony EX71SL earphones, which has a nasty little spike in one treble frequency area.
I found a similar such filter on the likwitz website: http://www.linkwitzlab.com/reference_earphones.htm
But my output impedance is much lower and my frequency center point higher. I'm having trouble calculating the values I need for the filter to work with my devices/amps. I've played with online calculators, such as http://sim.okawa-denshi.jp/en/RLCbekeisan.htm but I still can't seem to generate a similar notch depth AND Q value at the same time.
Here are my devices and their output impedances:
Apogee Duet: 32ohms - iPhone 6: 3.18 ohms - C5 amp: 2.2 ohms - Sansa Fuze: ~1 ohm
Center frequency: 6,000hz
I was thinking I can use the 32 ohm for my calculations and simply add a 30 ohm adapter to my other two devices, thus essentially giving me roughly 32 ohms for each device when used.
He lists a Q value of 17, but I'm using EQ apps with lower values. I'm using a 7.2 Q value or 0.2 BW (bandwidth) if you want to convert it to that.
These result in a perfect reduction of the 6,000hz treble peak as found with a sine sweep.
Using the values on his site result in a different amount of reduction and whatnot if I plug them into the online calculator.
Can someone tell me what values I would need to use to achieve a 7.8 or rounded to 8.0db reduction at 6,000hz with a 7.2 Q if my output impedance is 32 ohms, and would it matter if the output is off by 1 ohm on each device? How much would that effect the shape?
I'm starting to understand some of the equations, but I can't seem to isolate the exact relationships and what I need to do to arrive at these values even just putting in values on the online calculator and trying to tweak them.
Any help would be greatly appreciated.
Amplification shouldn't be an issue either. The C5 seems to easily drive these earphones well past iphone levels and much louder than I'd ever use.
I'd love to understand this all, so any detailed responses would be great.