[Bill-P]

Please go to post #6 if you are looking for a way to reduce the treble of the DT770 for good. May also apply to other headphones!
 
I'm getting really good results modding the DT770, and the sound that I'm hearing is pure bliss!
 
Plus quite a number of people were interested in knowing what I did to the W1000X, and also the ES10 to get them to sound that way...
 
So I have decided to keep a diary of what I did to the DT770, and also a list of changes to the sound (purely subjective, since I don't have any measurement device other than my ears). If you're raring to mod your DT770 and get some more bang for your bucks, I hope this will be of use for you.
 
Materials:
 
Dynamat Extreme or equivalent
Felt and foam pads (you can buy these at art and craft stores)
Microfiber clothes (the kind that you use to wipe your glasses), preferably thin ones so that you can control how much they dampen
Your patience (this goes without saying)
 
Process:
 
For starters, here's how to disassemble your DT770:
http://www.head-fi.org/t/645691/disassembly-how-2-on-beyerdynamic-dt-770-pro-80-ohm-with-photos
 
I followed the exact same steps, but please make sure to stop before you take apart the drivers! It's not easy to pry them out, unless you are handy with heat guns and soldering irons in order to do a clean job, and then you still need some glue.
 
You should have the bare driver enclosure out like this after you have finished disassembling your DT770:
 

 
From experimenting, I think that felt ring around the enclosure is there to control air flow into the chamber. The DT770 Pro's enclosure actually has a small port/opening right around the right-hand side of the ear cup that lets in some air. The air is not to make the sound "airy". Quite the contrary... it's there to make sure there is enough air for bass, because bass impact pushes a lot of air.
 
Anyway, TLDR: take off the felt ring if you want moar bass than the unholy amount that the DT770 already has.
 
I was going more for control, so I thought... how about dynamat on the back of the plastic enclosure to reduce excess vibration? Hmm..
 
So I cut a small piece of felt to approximate the size of each of the 4 slots in the back of the driver. Not sure what those slots are for... although I suspect that more elaborate "devices" can be put there should Beyer need to provide more dampers for their headphones.
 

 
Once I know the right size, I can now cut out pieces of dynamat that would approximate the size of the felt that I used to measure the slots...
 

 
And naturally, the dynamat will fit:
 

 
Cool, so that actually allowed for far cleaner and controlled bass without reducing the quantity. Also it helped cleaning up lower midrange frequencies to my ears.
 
But that's not all. I wanted far cleaner bass than that would give me, so... dynamat was also applied to the ear cup:
 

 

 

 
Last but not least, if you want to tame a bit of that treble but at the expense of airiness and clarity, then cut out a piece of felt that's about the same size as the felt pad that was on top of the driver.
 

 
And then lay it inside the ear cup like this:
 

 
More felt pads will dampen high frequencies a bit more, though there's not a lot that that will do to sibilance, which is resonance at around 8-9K.
 
The felt pads will also dampen bass slightly since there is less air inside the chamber.
 
That's purely for bass control. In the mean time, I have done more than that in order to bring out midrange. When I have more time, I'll post up what I did in order to get more and fuller midrange out of the 770 without sacrificing clarity.
 
To be continued...

 

[Bill-P]

Reserved for future use since I get the feeling I'll try a lot of things... 

 

[beedee]

Hey Bill, Did you ever finish?

 

[Bill-P]

Hey Bill, Did you ever finish?

Yeah, you bet!
 
Let me take some photos, and then I'll post some instructions, plus measurements (gotta be scientific, haha). I had CanJam to be my test bench, and everyone at CanJam, including DT770 owners, could notice the difference.

 

[beedee]

Thanks! I'm very interested in the measurements.

 

[Bill-P]

And... here's the moment you've been waiting for: a real way to noticeably reduce the treble of the DT770 (and may also apply to many other headphones).
 
What you'll need:
Bounty Paper Towel. Specifically, this kind:
http://www.amazon.com/Bounty-Paper-Towels-Prints-Count/dp/B00I4F1W78/ref=sr_1_2?ie=UTF8&qid=1428367432&sr=8-2&keywords=bounty+paper+towel
 
(note: it has to be exactly this kind. No other kind of napkin or tissue I have tried would work)
 
Felt: (any color is fine)
http://www.amazon.com/Darice-FLT-0499-Felties-Sticky-Primary/dp/B004N5L1ZQ/ref=sr_1_2?ie=UTF8&qid=1428367542&sr=8-2&keywords=felt
 
Shelf liner: (any color is fine)
http://www.amazon.com/Duck-1100731-Non-Adhesive-12-Inch-20-Feet/dp/B002AS9NAI/ref=sr_1_1?s=home-garden&ie=UTF8&qid=1428368182&sr=1-1&keywords=shelf+liner
 
All of those can be gotten for cheap, so I'd recommend group buy or something like that to reduce cost if you have to order from Amazon. Bounty is probably already in many American households.
 
Instructions:
Open your DT770 up and remove the retaining thing, then remove the foam piece covering the driver to reveal this papery surface:


Cut out some circular pads of the Bounty paper towels, then lay them over the driver like this: (my DT770 needed 3 layers, but yours may need less)

 
Then put one layer of felt on top:

 
And finally, put one layer of the shelf-liner I mentioned:

 
Then... close the headphone up and enjoy!
 
Measurement of frequency response before and after:


Notice how treble from 6KHz and above dropped almost 10dB. This made the DT770 much more linear to me. Bass also seems to have increased slightly.

 

[beedee]

Thanks Bill!  Never would have thought about trying shelf liner, cool.  Did you do measurements after adding each layer of material?  Just curious about the process.  Also curious if:
 
1 - you ever removed the black circular comb and white felt around the driver and did measurements.
 
2 - removed the white cap over the back of the driver and did measurements.
 
I have the 32 ohm LE version and it doesn't have the comb or the felt around the driver, just the white cap.
 
Nice work!

 

[UmustBKidn]

I was one of those who got to hear Bill's mods at CanJam. I can attest to the fact that this does indeed make this headphone less strident and smoother sounding.
 
(When I walked into the Member area, Bill said "Finally, someone wearing DT770's" lol).
 
I own the 250 ohm version, so I don't know if that would make a difference or not. Anyhow, the cable on my set is getting a bit worn from movement, so I may combine cable replacement with this mod at some point in the future...

 

[c61746961]

Bill, have you played with medium density foam inside the cups to see if it helps with the midbass dip?, I have had some success with it.

 

[Bill-P]

Yeah, I have tried a lot of things to see if I could remove that dip. I think it's an effect of the enclosure being closed back, and that right there is the frequency at which the reflecting backwave from the driver cancels out a part of the wave in front. Acoustic foam helps move the dip up or down, but that also drops bass because the driver isn't getting pressurized in the back, and the front is more pressurized, impeaching diaphragm excursion.
 
A new semi-open enclosure may help after all, but that would be quite a project to undertake. I do have something like that planned, though, so... please stay tuned. For now, this is the easiest way to drop treble noticeably with the DT770/880/990 headphones.

 

[Armaegis]

Maybe we need some diagonal baffling in the cup to offset those reflections.

 

[ManicMaurice]

Sorry to resurrect an older thread, but I'm intrigued by this mod. I had already added the paper towels on my own before I ever found this thread, but I keep vacillating back and forth between 1 layer and 2 layers, instead of the recommend 3 layers. I did find that 3 layers does make the high-end much more balanced with the mid-range, but I don't really want to lose the fun V character of the 770s entirely. Different strokes for different folks.
 
What I'm really interested in here is the theory behind the materials used in this mod. What are you trying to achieve with each of the separate layers - paper towel, 1mm felt, and shelf liner? And did you reinstall the stock black center foam or did you leave it out after completing your mod?

 

[Bill-P]

Hey, Manic.
 
Sorry, I've been busy, so I didn't update this guide. I've arrived at a better solution than this (with measurements, too), so I'll find the time to write that up.
 
And the initial theory for the layers of different material is that... they each have different attenuation properties that work best at some specific frequencies, but not at others. Since headphones, even in the same family/model/line have some variations in their high frequency response, it's best to try different things and taylor the tuning to your own needs. Basically like EQing, but more on the acoustic side.
 
An EQ can be applied to achieve pretty much the same effect, I think, but an acoustic modification would always allow for more versatility because you're not imposing a software limit on the signal, and you're not limiting your headphone listening to just a system where you can apply that EQ, so... say, this will work equally well when you go to watch Youtube, and not just when you use EQ to listen to music in Foobar, for instance.

 

[ManicMaurice]

Originally Posted by Bill-P /img/forum/go_quote.gif
 
Sorry, I've been busy, so I didn't update this guide. I've arrived at a better solution than this (with measurements, too), so I'll find the time to write that up.

 
No worries. Thanks for getting back to me. I anxiously await your new findings.

 

[Z3ph3r]

  Hey, Manic.
 
Sorry, I've been busy, so I didn't update this guide. I've arrived at a better solution than this (with measurements, too), so I'll find the time to write that up.
 
And the initial theory for the layers of different material is that... they each have different attenuation properties that work best at some specific frequencies, but not at others. Since headphones, even in the same family/model/line have some variations in their high-frequency response, it's best to try different things and tailor the tuning to your own needs. Basically like EQing, but more on the acoustic side.
 
An EQ can be applied to achieve pretty much the same effect, I think, but an acoustic modification would always allow for more versatility because you're not imposing a software limit on the signal, and you're not limiting your headphone listening to just a system where you can apply that EQ, so... say, this will work equally well when you go to watch Youtube, and not just when you use EQ to listen to music in Foobar, for instance.

I am thinking about getting a premium 32ohm version on eBay, but I am very sensitive to treble. Have you tried any mods on that model?