[ortho transplant] Fostex T50rp drivers into a Beyerdynamic Custom One Pro

[Armaegis]

They say idle hands are the devil's playthings...
 
 
Look what arrived the other day. Feature of note: variable bass vents! This should be interesting. 
 

 
Why yes, I think I will...

 
blah blah blah, I didn't actually read any of it

 
hello my pretty, I will be gutting you soon

 
a small screwdriver is all you need to pop the retaining ring off

 
this fuzzy disk is actually important to prevent the baffle/driver from vibrating against the retaining ring and mounting tabs underneath

 
oh she's naked now!

 
naked from the backside, you naughty thing

 
the jack actually plugs into a "hole" in the bottom of the cup, and is held in place with a single screw

 
it comes out quite easily

 
For those curious in how to remove the T50rp drivers, see my earlier transplant here: http://www.head-fi.org/t/648893/ortho-transplant-t50rp-drivers-into-v-moda-crossfade-lots-of-pictures
 
Now let's check for fit/clearance... eek that's going to be tight

 
wow, not much depth clearance either (the baffle sits on top of the ring of ridges)

 
In an effort to keep things as non-destructive as possible, I needed some new baffles. Big thanks to Jason from http://www.customcans.co.uk/ who cut these out for me

 
I mentioned this was a tight fit right?

 
a lot of fiddling and twisting is required to actually get the thing to fit
(that's what she said)

 
Hmm, while we're at it...

 
Let's add a hole on the backside (after taking out the shield of course). Maybe it'll add more base, maybe not, but if it doesn't work we'll just cover it back up.

 
Standard stuff, put some acoustic foam in the cup. Some more pieces were fit in there to cover up the gaps. Twaron angel hair (acoustic filler) in varying amounts was later stuffed in. 

That post in the middle actually presses against the stock driver for stability. For that reason I did not remove it, as I am trying to keep everything reversible. 
 
 
I do have a 4-pin mini xlr jack... not going to install that at the moment... maybe later

 
 
it looks like it'll just barely fit, but I don't want to damage the bass vent slider either

 
This is the left side, which was considerably harder to get to fit properly because the jack eats up a lot of valuable space inside. Those arrows indicate the *only* orientation that I could find where the baffle and driver actually fit into the cup

 
Put it back together with the fuzzy disk, and a piece of soft felt on top of that

 
Boom. None the wiser. 

 

[Armaegis]

reserved for other notes, experiments on damping, changing pads, and the effects of the bass vent slider...
 
 
 
 
needs that foam disk in front to prevent driver rattle
 
just bare transplant
- argh treble spikes
 
added acoustic foam and angel hair
- phew
 
double the angel hair
- treble down a bit more, but starting to feel a bit stuffy
- will have to come back to this, maybe do 3/4 the amount
 
drilled hole
- slightly more bass
 
put some velour into the hole
- oops treble spike came back up and lost a bit of sub-bass
- removed the velour
 
pads
- stock: holy balls treble from 2-3kHz
- J$ Beyers: better bass, slightly wobblier treble
- J$ Denons: more bass and better extension, more mids, narrower spike at 2.5k
- Shure 840: haven't tried yet
- HiFiMAN velour: haven't tried yet
- HiFiMAN pleather: haven't tried yet
 
felt in front of driver
- reduce & broaden the 2.5k spike
 
bass vents slider
- more like an attenuator rather than a boost at this point
 
close the baffle hole
- better bass extension
 
output impedance
- high: more bass rumble and feels like it extends lower, but seems like treble spikes more too and rings?
- low: flatter, less oomph, but less aggressive highs too
 

 

[Armaegis]

reserved because I feel like it

 

[kramer5150]

Holy moly!... nice job.
 
Curious how well do those drivers do in an open earcup?.. does the bass and lower midrange warmth disappear without a closed earcup behind it?
 
thanks

 

[nick n]

What is the orientation of the Fuzz?  It is facing the earside is it?
 
Can you post pics of the front view facing the earsides when you get to it, sometime, whenever sort of thing. 
 
Are the pads dreamy?
 
I don't need to say excellent job, so i won't

 
here's hoping the fine tuning is easy, and that the variable bass vent is effective

 

[Armaegis]

Quote:

Holy moly!... nice job.
 
Curious how well do those drivers do in an open earcup?.. does the bass and lower midrange warmth disappear without a closed earcup behind it?
 
thanks

 
Thanks. I've been pondering the open concept as well. I've asked a couple other guys who've tried variations on that theme and they did not report much success. When I get my Crossfade transplant back I'm going to try making it open backed. If that doesn't work, I'll just put the shield back on.
 
On the COP, opening the slider does result in more bass, but the effect isn't quite as drastic as with the stock drivers. 
 
 
Quote:

What is the orientation of the Fuzz?  It is facing the earside is it?
 
Can you post pics of the front view facing the earsides when you get to it, sometime, whenever sort of thing. 
 
Are the pads dreamy?
 
I don't need to say excellent job, so i won't

 
here's hoping the fine tuning is easy, and that the variable bass vent is effective

 
Front view? Like on a dummy head or something? (I think I have one of those somewhere)
 
So far I'm liking the J$ Denon pads on them. Haven't had too much time listening yet though. 

 

[nick n]

Front view as in earside baffle face with pads goodness view..

 

[jfunk]

Nice work Glad to see the baffles arrived and looks like the fit ok as well.

 

[Armaegis]

Yeah, thanks a million. The wooden ones unfortunately did not survive the trip, but the poly ones work just fine. I had to breath a sigh of relief that I actually got the left side to fit. I should have realized that I would need to offset just slightly to account for that 3.5mm jack, but luck (and a little bit of grunt) was with me. 

 

[dBel84]

Great work ! The effort looks well worth it thus far ..dB

 

[Armaegis]

Quote:

Great work ! The effort looks well worth it thus far ..dB

 
Gracias! I haven't played around with them too much, but even with the initial setup I'm liking the results so far. Just gotta eek out a little more subbass response.
 
Quote:

Front view as in earside baffle face with pads goodness view..

 

 

The J$ Denons installed. J$ Beyers below left, stock pads to the right.

 

[Armaegis]

Interesting note: there's a peg in the centre of the cup. With the stock drivers they actually rest on top of that peg, compressed onto it with some dynamat like material. I imagine this provides a lot of stability for the entire driver/baffle assembly. Because of this, I did not remove it in case I want to return to stock. It did make me wonder how it would affect sound however. Would it be like a funnel? Would it amplify anything? I also punched a hole into it... 
 
So anyhow, I stuck a small piece of fuzzy breathable velour into it thinking if there were any sort of funny business happening in there, the velour would damp it out. Boy was I wrong. Stuffing the hole (heh) decreased bass extension (which I expected), but actually increased the treble as well. Now the bass part I can understand as that's essentially increasing the overall bass venting. The treble part... I guess having a hole behind the driver just lets out all that energy. Anything behind it, even the breathable stuff, winds up reflecting. 

 

[Armaegis]

I was also surprised to hear a difference between output impedances. 

 

[roma101]

Amazing work Nathan and great photos!! Looking forward to more of your impressions as you tune that beast.

 

[Armaegis]

Thanks. I'm actually pretty happy with the current config: acoustic foam in cup, some twaron on top, nothing else in the cup. All holes on the baffle are sealed (I had 4 holes drilled in matching the holes on the driver). In front of the driver is the stock foam disk, a piece of soft felt, and the mesh on the J$ Denon pad. 
 
With the bass ports fully open, the sound is overall bass sloped. Not crazy bassy; just enough to feel well extended. Midrange dips down a little bit like an Audeze. There's a lower treble spike but that's tamed down by the felt. Maybe lacking a bit in air, which is again possibly due to the felt. I'm a bit of a treble hater at times, so that reflects in my usual damping schemes. Soundstaging is decent, and I'd say slightly above average for a closed can. Isolation is very very good.