What happens when you put a T50RP driver into a pair of DT990's...

Yes, I really did that, and this is the .REW measurement of it:
https://www.dropbox.com/s/c3c6uodq0tfdzwv/MK990.mdat?dl=0

picture of the measurement:


I would have hoped to get a bunch more sub bass out of these, but I think that will require some quite extreme measures to pull off, and some very specific materials and stuff. It's also still an open headphone, so unless I get wooden covers made to replace the grilles, it won't get much better than this.

To get it to look this nice, I had to do some modding to the driver, and I had to get the right balance of dampening materials in front of and behind the driver. Also, I stuffed the HM5 pads with Sennheiser replacement pads. Yes, seriously. It actually did a lot to smoothen things out and firm up the pads!

With more clamp, these could potentially be a LOT more bassy if my measurements are any indication. That could just be the result of me cupping my hands over the grilles too though, who knows.

Anyway, this was quite an adventure to work out, and I'm glad It sounds good right now. Nice deep punchy bass, good detail across the spectrum

 

Just slap some DT770 pads on.
They look the same but aren't and have a LOT more lows

 

I have hm5 angled pleathers on actually. dt770 pads didn't work out too well.

 

Why do you feel subbass extension isn't that great ?
5Hz at the same level as 1kHz seems enough extension to me.
20Hz is already +8dB.
Do you want even more boost there ?
EQ may be your best bet ?

 

Hey neat! This was my Beyer transplant a couple years ago: http://www.head-fi.org/t/656644/ort...rp-drivers-into-a-beyerdynamic-custom-one-pro

Looks like you did a pretty good job tamping down the Beyer treble issues. The COP cups are a bit shallower (and have that funny peg in the middle) so there's less room for stuffing in there.

Did you make your own baffle to mount the T50rp driver?

 

Basically, I had a friend of mine CNC some baffles for them. Your transplant informed my own!

tip: stuff TONS of cotton into the cups, and use really thick layers of felt stuffed onto the rear of the driver. Also, cut out the paper from the middle square on the rear of the driver (don't do this without dampening in the cups). That'll allow the driver to move a lot more, and then the cotton will dampen the mid-bass bump that it wants to make when that happens.

I take no responsibility if you mess it up

 

Hah, cool cool. Glad you took some inspiration from it.

At this point I'm not so inclined to open them up anymore. Because I didn't offset the driver on mine, the fit is *very* tight and is already compressing the wires a bit so I'm uncomfortable putting any more strain on them than is necessary. At the moment there's acoustic foam and filler (twaron angel hair; fantastic stuff) in the cups. I have soft felt and the stock foam disk in front of the drivers.

 

Sub extension is fine, mid bass level is not. I want more sub bass relative to the mid bass, but so far the challenge has actually been to reduce the mid bass. So either I get more sub bass, or I get less mid bass, whichever does what I want

 

I wonder if you could close some of the exterior vents and then open small holes to tune the mid/sub-bass to your desired balance sort of like subwoofer porting? I know that BMF's measurement megathread seems to imply that this is possible if you look at the results he observed in this process with the t50 housing.

 

I fully encourage any and all wacky experiments

 

20Hz is at nearly the same level as 100Hz. I can't imagine it can get much better than this from headphones. How much actual music has stuff going on below even 40Hz? Not a lot.

 

Actually I find that most of my music pushes down to 30 or even 20Hz just from instruments bleeding downwards (verified using spectrogram). By artificially boosting the sub-bass below 50Hz, I feel like music feels more full-bodied. This is especially true of the t50mk3 at stock in my opinion, most of my modding experiments have been directed at addressing the thin and somewhat sibilant sound that these headphones have once you use deeper pads.