[fjhuerta]

((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.
 
 
The story:
 
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. 
 
 
The solution:
 
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!

 

[mcandmar]

Are you dissatisfied with your Grados?   Nope, i found the Ms-Pros

 
Seriously though if you find the MS1's too bright dont ever try a regular Grado or your head will implode.  I really dont think analog filtering is a solution when something like a HD650 might be more your cup of tea, just saying..

 

[JoeDoe]

This is an interesting idea, but I too think that maybe you just need to find a different can. Or maybe do some software EQing?
 
After all if the girl ain't the one, no amount of makeup, lingerie, or pillow talk gonna transform her

 

[fjhuerta]

I remember my Ms-1s were more balanced and listenable - enjoyable . Since I put the wooden cups and wire something happened to the frequency response. I don't know what, or if I'm imagining things and they always sounded like this. One things for sure, both drivers measure the same, so they can't be damaged. If there's something wrong, then it had to happen to both drivers and affected them the same way. Impossible. And wire can't make that much of a difference.

I don't remember the MS-1s being so shouty and harsh. But I liberated the drivers properly - they are fine. I don't think wooden cups can make such a drastic sound change, either. If anything, they should be warmer. I'm at a loss of what could have happened...

Software EQ does help. But I don't want to have to use the headphones all the time with a source with EQ.

I know it's easier to just use my hd-580s. But there's no challenge on doing that! It's all about doing something new and having tons of fun along the way.

 

[Aizura]

I'm probably the only headfier that found the MS1i to be brighter than the SR60i (and I've heard 3 different SR60i).
Maybe I had a late friday pair of MS1i.
I was like: this is balanced? It had like NO bass. Less than K701 bass. Mids were definitely further in the back than on SR60i, but that only makes them more harsh to me

 

[squallkiercosa]

There's a guy who put some resistors inside a akg 550 to tame the treble. Have a look

 

[fjhuerta]

  I'm probably the only headfier that found the MS1i to be brighter than the SR60i (and I've heard 3 different SR60i).
Maybe I had a late friday pair of MS1i.
I was like: this is balanced? It had like NO bass. Less than K701 bass. Mids were definitely further in the back than on SR60i, but that only makes them more harsh to me

Yep. I had a set of 501s and they had more bass than my MS-1s. And were far better balanced. Listening to my MH-1s after the Grados feels incredible... so smooth.
 
The only thing I changed that could have affected the sound badly are the bowl cups I got. I used to have the original pads.  I wonder if that's the issue. Or if there's some leakage between the driver and the cup, and I'm killing the bass.
 
Either way I'm going to make my Grados sound as much as I can like my Sennheisers. Weird, huh? But hey, I'm not willing to sell my headphones now. They are too nice looking. 

 

[brhfl]

I'm on board with this crazy plan... I've never been one for the Grado sound, but I like that they're made domestically, and I like how modular they are, the wealth of cups available, etc. Will be watching this space...

 

[fjhuerta]

I wouldn't be surprised anyone thought I had forgotten about this, but I had quite a bit of work to do.
 
I'll post the way I arrived at this solution, but suffice to say, given the interest on Sean Olive's reference headphone curves, this could be an approach to get them (on some headphones).
 
Anyway, here's the final FR trace. I had to build a jig to measure the headphones, took every measurement myself, including impedance, and got this. I ordered the parts I need to build the circuit, so I'll keep updating this thread when I finally do it. Although, I already simulated the transfer function via software, and I'm very, very impressed at how good the headphones now sound.
 
Blue trace is the original measurement of the Grados, red trace is the one with the filters applied, black trace are my trusty Sennheiser HD-580s I used as a reference.
 

 
This is the preliminary circuit. I need to spend a couple of hours on Digi or Mouser and find what kind of values I can get for the parts, so consider this as an alpha version of the solution.