RLC notch filters
Oct 20, 2008 at 2:59 AM Thread Starter Post #1 of 6

Jonomega

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Right now, I am using IIEQ through Foobar2K w/ VST plug in. I am interested in getting the same effect but for all programs and figured a hardware solution would do this as I haven't found a soundcard level software that could do it.

I have zero experience with electronics/soldering/circuitry, but I figure it shouldn't be too difficult to learn.

The two filters I would like to reproduce are

Gain: -8 dB
Freq: 7000 Hz
Q: 4.8

Gain: -10 dB
Freq: 9000 Hz
Q: 4.8

Any ideas?

The headphones are Grado SR-125, and I do not use a headphone amp. The input would be soundcard into the notch filters into the headphones.

Thanks in advanced!
 
Oct 21, 2008 at 12:34 AM Post #3 of 6

nikongod

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Considering the "proximity" of the 2 target points: For a passive solution, you may prefer "simply" picking a target in the middle, and widening the notch. you will likely find that this allows the use of only one filter with a similar end result.

As another note: the 8khz "range" is particularly vile with headphones due to inner-ear resonances. your desire to "reduce" the level at this frequency is not unusual. senheiser has said in the past that the "dips" at 8khz were designed INTO the hd-580/650 headphones for this reason.
Quote:

Originally Posted by Shoewreck /img/forum/go_quote.gif
I doubt such a filter is possible without an amp, especially given it has two stages and given high Q's.


QFT

You could do it with high impedance headphones, or a lower damping factor, but it would be VERY dificult to accomplish as described for a grado.

It would be MUCH easier if it were a passive notch filter at the input of an amp... I would try at least a simple Cmoy with a good powerful opamp.

you may find this link helpful
link
 
Oct 21, 2008 at 3:27 AM Post #4 of 6

Jonomega

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Interesting posts guys. I was not aware of the power problems due to my headphones being of low impedance. I've played around with using a single lower Q digital PEQ notch setting and it didn't sound as good, nor chart out as nicely.

Interesting that you brought up sennheiser. I used a friends HD-555 to help me dial in my grado's. I like the bass in the grado's better than the sennheiser, and the senns sounded too dull and lifeless while the grado's had too much. The filters bring the upper end response close to what you would expect from the senn but with 2-3 dB more overall in the >2 kHz spectrum which I prefer. I didn't buy a senn because I like how the Grado has a stable impedance profile with a low enough value as to not require an amplifier.

Thanks for the link to SL's work. I have read his Orion stuff but I didn't know he had done some headphone work.

I'll try to tweak my VST PEQ to sound ok with 1 notch rather than two as it seems 1 notch is far easier to build than 2.

I'll search for some info on the CMOY. Has anyone integrated EQ into their CMOY for 1 "clean" package?

If so, I'd love a link to that, perhaps it will give me some ideas.
 
Oct 21, 2008 at 2:39 PM Post #6 of 6

roggom

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I have the SR125's and they tend to be quite bright on some formats. This sounds to simple, but I switched the flat pads of my SR60's onto the SR125's and it sounds right to me. The bowls on the sr60's was a great compliment.
 

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