((Note: I know many people love the Grado sound. I don't. Different strokes for different folks and all that)).
So, you bought your Grado headphones and find them too bright, and want to tame them. I know I want to.
What this thread is about...
This is not a thread about hocus pocus fixes (ie, new wires, tube amps, etc).
This is not a difference you may or may not hear. You *will* hear it.
It'll be adjustable. Dial-in (or out) as much treble as you want.
I'm going to try and make my Grados sing. I mean, -3, -4 dB's at 2, 4, 5, 6, 7, 8 KHz. The real deal. Airy upper highs, controlled mid and low treble, untouched bass response.
It's going to be somewhat easy to do.
And it's not destructive. You won't need to take your Grados apart. You won't void your warranty.
I just rewired my Alessandro MS-1s, got them wooden cups, leather headbands, etc. and I had forgotten how stupid bright they are (at least for me).
But oh man. They are beautiful. I want to keep them, enjoy them... what to do?
I tried all the usual mods - tape on foam, felt pads on top of the drivers, etc. They don't work.
So I took an FFT analyzer and fed them some pink noise. I saw the ugly peaks at 2 KHz and 8 KHz or so. They are big. They are there. And they hurt. Big time (at least they hurt me). I repeated the test with my Sennheiser HD-580s. No peaks. No wonder these things hurt! Something needed to be done.
Adding pads, felt, etc. really doesn't help. Pads and felt kill most of the upper end - you get rid of lively treble and the headphone becomes rather dark. Not good.
EQ *does* help. Getting rid of the nasties is easy by dialing -3 or -4 dB at the offending frequencies. This proves the peaks aren't coming from the driver breaking up (at least too badly). I couldn't detect much distortion higher up (could be there, and it could be the source of Grado's liveliness).
But I'm not going to live with an EQ curve exclusive for Grados. Eventually, I'd like to use them with other equipment.
I read Sean Olive's post about the perfect headphone frequency response... and it got me thinking. Sean Olive is one of the people I admire the most in audio. He's the real deal, no black magic - just facts and measurements.
So, after considering what he wrote, watching the Grado's FR curve, and remembering I've been designing speakers for close to 10 years now. And have all the measuring equipment, I finally figured out what needs to be done...
...design either a parallel or a shunt trap filter to get rid of the extra HF peaks electrically. Add it in line, in front of the RCA connector. Keep it inside an Altoids tin can. Use a high quality R, L, and C. And *finally* get rid of the brightness. I'll keep a nice custom made Grado headphone with the best (to me) FR I can get. And if anyone is interested - all you'll need is an Altoids can, about $10 (tops) in electrical parts, some wire and jacks.
I still don't know whether the R, L, and C values will be small enough to fit inside an Altoids can. I hope they will (actually I'd love to house the components inside the drivers enclosure. Wishful thinking on my part...)
It's not a new idea. Siegfried Linkwitz did it for the Etymotic ER4-S. But hey, we arrived at the same idea independently (not really, I'm sure he influenced me. I'm also a fan of his work).
How I'll do it:
I'll measure impedance on one of the drivers, then I'll take an MLS 3 or 4 cms away from the driver in order to get a free field response (or something at least remotely similar like that). Then I'll take a FR response of a Sennheiser HD-580 as a control. I'll use a simulation tool to design a filter and then try the whole thing until I get something I like.
I'll document everything I do here.
It'll probably take 2 - 3 weeks (too much work to do!). It's pretty simple stuff - basically a one way speaker with a trap filter.
It should be a fairly simple 1 evening affair... that is, if I could get some time off!
Edited by fjhuerta - 2/6/14 at 8:18pm