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Fostex Mods for T20/40/50/(60) RP series Mk3

  1. Light - Man
    Let us collectively help each other by posting our DIY Mods that we have tried and like or even dislike.

    Also any interesting ideas that you plan to try in the future.

    Photos are always welcome.

    You can also copy and paste previous posts that you made on other threads or even post the links here (whatever you prefer).

    I have no experience with the previous older models or any of the well known mod packages, so feel free to mention and explain them here so that others will be informed of their options.

    New members are always welcome and don't worry about making a mess of your first post! Remember that you can always edit your post at any time.

    Perhaps we should try to concentrate on the Mk3 series because they all share the same driver and baffle plate across the T20/40/50 and even the new T60RP model.

    But if you think that you have something to offer us from your experience with older models then please feel free to post here.
    Last edited: Aug 12, 2018
    Artyouth likes this.
  2. rendyG
    OK, lemme start with a summary I wrote some time ago... Since then I made a lot more mods, mainly printing Alpha Dog cups and now I´m waiting for ZMF Oval Cowhide pads, coz I don´t feel I´m done with the mods yet :p

    Finally! After opening my cups many times I think I can say my modded t50rp sounds fantastic and I want to share my variation with you guys :)

    I will start with pads. After researching I chose HM5 Hybrids, excellent comfort, imho no better option for this price. They increase the highs (even the 12kHz+ which stock is somewhat missing) and make nice big soundstage.
    I also use 2-3 layers of really breathable thin foam on the ear side to reduce highs as I am treble sensitive. Some people use toilet paper - more drastic approach.
    Today I made a foam inserts to make the pads angled. Worked really nice as you can see in the second picture - brings the stage more in front of you.
    angledfoam.jpg angled.jpg

    Next one is comfort strap, you can buy it or you can simply do it yourself. I used some black elastic material, others usually use leather.

    If you are afraid to open the cups, I would recommend you to apply BMF dots / Mrspeakers Doggie Treats which in this configuration reduces imho very noticeable 9kHz peak and even adds more air!
    Then there are 8 baffle vents. By closing them you can increase the bass significantly. I have 4 vents closed, but without the inner dampening this can be too much.
    Mid bass can be reduced by closing external cup vents, you can basically transfer t50rp to t40rp if you close all four completely.. I closed three of them.

    Combination of the mods above can be enough to mod these headphones to your liking and they are all reversible.
    But if you want more, lets open the cups..
    Baffle: well known mass loading which tightens the bass, but adds weight, you have to decide.
    Driver: usually you will use stiffened craft felt, but I used thin soft black felt (secured with double sided tape) in combination with acoustic polyfill (not on pictures), you can also use wool, cotton.. By both of these you are controlling bass and increasing desirable sub bass extension.

    Lastly we have cup which I dampened with acoustic foam and then added ladder rungs.
    Previously I had this whole cup dampened with acoustic foam, but I think it was overdampened.. so I removed the foam from the middle column and instead of it used just stiff felt. I have also read that covering the pivot makes the highs less natural or something, so I left it uncovered. This smooths things a lot, removes most of the reflections and reduces the mid bass hump.
    Note I have no picture with cup filled with polyfill as mentioned above, this is the trickiest part. There are many options when choosing the material (polyfill, cotton, wool, fiberglass, rockwool, open cell foam..) if you want to experiment :)
    You have to use the right ammount and balance the sides. If you do it right, you will get nice, sweet, extended bass :p

    Thanks BMF, Mrspeakers, Mayflower and many of you guys on the forums. You all inspired me and I learned a lot by moding. I´m glad I have these awesome headphones which now sounds waaay above its price point. Wish I could A/B them against stock mk3 and other t50rp mods :p

    I hope this post will be helpful to some of you! :wink:
    Feel free to correct me, ask me or share your experience with this mod.
    Like appreciated :p

    EDIT: adding a FR from my cheap diy rig, the right driver has been replaced by a new one (stripped the threads). That could be the reason for the dips in midrange, also I haven´t tightened up the new driver, so that is another possibility.
    mk3 measurement.jpg
    vs HD580 coin mod, regrilled
    HD580 vs mk3.jpg

    vs T-X0 stock
    mk3 vs T-X0.jpg
    Last edited: Aug 10, 2018
    kintsaki, volly, trellus and 2 others like this.
  3. Artyouth
    Yes I just had T60 and Mk2 (and also an Open Alpha). I didn't have Mk3.
    However if I want a Mk3 I can make one myself. Not necessary to buy.
    I can just replace my T20Mk2 baffle(1st gen without vents) to a T60 baffle(2nd gen with 8 vents). Then, it is identically a T20Mk3 !

    What my T20 less then the T60 is not the treble. The T60 metalic treble actually is what I don't like. I have to tame that metalic treble by mouse-pad rings.
    I can't mod my T20 to the T60 sound, mostly on the speed and bounce, fun factors side.

    I was thinking what makes the T60 sound so speedy and bouncy, maybe because the 2nd gen baffle used. Or the wooden cup.

    My Open Alpha have cleaner sub-bass and extension, bigger mid-bass body then the T60, but not speedy bouncy.
    I think the actual answer just can found by swap the wooden cup and 2nd gen baffle to my T20mk2.
    Last edited: Aug 15, 2018
    Light - Man likes this.
  4. volly
    @Light - Man - Subbed.

    @rendyG - I too, like the hybrid pads. Love the mods you've done there mate! I've recently modded my T-X0's. Just the basics for now but much needed. Cotton in the cups, closed off 99% off the ports and hybrid pads. Definitely brought out the mids and high's that bit more. Bass is more present but I haven't started tweaking that yet. To control the high's that sometimes get shrill, I'm taking the approach like what Dan Clarke has done with the Aeon's, where he has optional inserts to tailor the sound further. I got some material like foam that I've placed inside the hybrid ear pads. Amazingly, it didn't suppress the high's anything drastically, but I do detect a noticeable smoother top end. I'm gonna try a whole bunch of other material and see what works best.

    Running them off a Darkvoice at the moment, plenty of power!
    Last edited: Aug 11, 2018
    Light - Man likes this.
  5. rendyG
    I liked hybrids from the start, but the highs can be little problematic, especially with mk3 driver, T-X0 should be okay, they are calmer above 2kHz. I actually just ordered ZMF Oval Cowhide pads, they are a lot more expensive, but they should reduce the treble peaks even more as Zach told me (I don´t have basic t50 anymore, but Open Alpha project from Mrspeakers).
    I don´t recommend using more layers of front damping, as it will make the headphones sound kinda lifeless..
    You mentioned Dan Clark, I recommend watching this video, using these doggie treats will dampen only some of the treble peaks and keep the extension, which is what we usually want, as T50RP driver has this 9-10kHz peak or so.

    I´m using the configuration with one dot in the back corner and one in bottom corner (as seen in the picture I posted in the second post above), this targets the peak the best, but depends on particular driver and your ears, of course..
    Last edited: Aug 11, 2018
    kintsaki and Light - Man like this.
  6. Artyouth
    I have a new thought about the treble reflector.
    Instead of directly contact the driver back, maybe an angled reflector will do something different. Especially may affect the nature of soundstage.
    I was inspired by what I found on the M1060 here:
    Post #7313

    However I don't think a Tx0rp have enough cup volumn(there is a centre pole) to add an angled reflector. Maybe will try it on the Alpha cup.
    rendyG and Light - Man like this.
  7. Light - Man
    Guys, I have been meaning to post an update on my simple to do mods but - what had started as a glass of wine with lunch (with a few of my wife's friends) in the garden on Saturday afternoon has taken me a few days too many to recover from. :ksc75smile:

    I intend to keep my mods as simple and easy as possible, as I just want to tweak the sound. I like the sound on the stock pads and have experimented with deeper pads and I always prefer the the shallower option. There are a few easy ways to increase the depth of the stock pads by a few millimeters which I will mention when I explore a bit more.

    My preferred signature is for natural pure tones and timbre with good presence and intimacy particularly in female vocals and instrumental music.

    I have gone through a phase like most guys of looking for a wide soundstage at the expense of other more important aspects that make the music sound like a real live performance. I, like most people really like good tight sub bass but I really dislike mid bass bloat that can mess up female vocals and sometimes can even swamp out treble detail.

    I think that the Fostex Mk3 series is surprisingly good at any price (especially for the money!!!) and I now understand why it has so many fans. Nothing that I have tried so far sounds so natural and uncluttered. I reckon that Tyll was mistaken when he said that he did not understand the fuss and extent that people went to, in order to mod them (even though I agree with most of what he has said on other gear that I have tried).

    I am a relative newcomer to the Fostex RP Mk3 series and I need more time to assemble my thoughts on any mods that I have tried and would recommend.
    Last edited: Aug 15, 2018
    kintsaki and Artyouth like this.
  8. Artyouth
    We have very similar personal preference such as shallower pads, intimated vocal, dislike mid bass bloat, don't look too serious on tight bass and soundstage but more on timbre etc.
    And I also believe less daming to achieve my prefered sounding is the key. Too much moddings will have too many compenstations on here and there.

    Hope will see your version on mod. I think I will get big benefit from you becasue of our same taste.
    kintsaki and Light - Man like this.
  9. kintsaki
    ----*--- T50 RP MK III Mayflower V3 Heavy Bass model -----*----

    I would like to start following this thread.

    I agree with most of the Artyouth's and Light-Man's opinions and tastes as expressed in their postings on other threads.

    I appreciate their efforts (including those of rendyG) and sharing of their findings while here at Head-fi while experimenting with various mods.

    I would like to point out that the Mark II's are acoustic suspension type ear speakers while Mark III's are transmission line types.
    Size of the enclosure and material filling the empty space are the key factors on Mk II's whereas size, length and material filling the path of the
    back wave signal as it travels from the back of the driver to the front to reach the front wave and combine favorably with it are the most important
    factors for the Mk III's.

    I have 2 Mk II's namely my ring modified (enlarged enclosure all wood including baffle) Smeggy Thunderpants and ZMF Blackwood special edition.

    I also have 4 Mk III's namely T20 (1 year old ), T20 ( with new T60 driver), T60, and my just acquired T50 MK III Mayflower V3 heavy bass model.

    I will report on the Mayflower Heavy Bass mod as soon as I have taken it around on all my test drives. For now lets just say that it is a phenomenal
    mod that can be tuned by a regular user with no technical shills or special tools to achieve a number of things not possible with any other mods.

    I use ZMF pads on all my RP's but I have the original pads and some Shure and HM5 ones.

    Some people reported some problems with the T60's (metallic highs, hot highs etc.) which I have been able to duplicate but I must tell you
    that these are caused by the source and or the amp further up the chain.

    If you are using a USB DAC without a full fledged purification system such as the ifi USB 3.0 Nano

    and or a headphone amp instead of a speaker amp you are not anywhere near the potential of the RP's.

    the ifi Micro DSD black edition with its built in purifier despite its "huge" power output and its
    purification circuitry will generate metallic highs, hot treble etc. on the T60.

    My rig is

    Intel i7, Nvidia 1060-->ifi USB 3.0 Nano--->Sony pha-3----->ifi Micro DSD black----->LH 055 step up adapter ----->Crown 10020II XTi 2------->Headphones
    RP headphones are compared to my dynamic Alessandro MS Pro, Focal Elear, and Fostex TH-900 and to my Orthodynamic Mr Speakers Ether C Flow,
    Hifiman He-6 and Edition X V2. I used to own Audeze LCD 2 , Monolith M1060 and Stax Omega 2 (all of which I gladly got rid off while owning the RP's).

    I have a systems approach so I would appreciate it if you take a minute to state your source, usb purification if any and amplifier so I can visualize your
    rig and integrate it to your comments.
    Light - Man and Artyouth like this.
  10. Artyouth
    Glad to see the Tx0rp modding game keep alive.

    About the differences between mk2/3 baffle. "the path of the back wave signal as it travels from the back of the driver to the front to reach the front wave and combine favorably with it"
    This part made me confuse. Because I didn't see any path from the driver back(cup side) to the baffle front. The only way let the backwave travels to front are the driver film I think.
    I always misunderstand that the purpose of the mk3 baffle vents is release the pressure of the driver(front pressure).
    Could you please explain this further?

    Yes the hot high on T60 maybe the chain thing. But how comes my chain just produces this hot on T60, but not my other T20 (stock or mods also not hot at all)?
    And there are quite a number of members here also get this hot on T60. I'm more believe this's caused by Fostex want to push the clarity of this can.

    I always want to put POWER on these cans as your repeated advise. Shame that I can't get that secondhand XLi1500(too late to press the button).
    I really want to see the real face of these rp driver. However I can't convince myself to buy a new amp without knowing the exact result. And my only one speaker amp just give me massive noise floor from his speaker out...

    kintsaki can you give me advise how to try this POWER on my limited gears? Or more accuracy to say, how to get POWER without noise. Thank you.
    Windows7 foobar2000(wasapi) > Topping DX7(coax in) > creek4140se(rca in)

    Thanks god I finally figured out how to upload pic.

    Last edited: Aug 18, 2018
    Light - Man likes this.
  11. Artyouth
    Just tried an angled reflector last night.
    Yes it really did somethings that I expected, but it also show me how limited I can get from this idea.

    It looks like a wave guide but it actually works mainly on reflection.


    - It doesn't contact the driver directly but it still works as a traditional treble reflector. You'll get high, you'll lost bass, you'll lost soundstage etc. Same as you directly put felt, dot, card on the driver.
    - You can tune the reflection factor more easier then the traditional reflector. By adjust the jalousie angle.
    - It will shift the position of soundstage dramatically! It depends on the angle and direction of the jalousie.

    - Lost bass and soundstage more then the traditional reflector.
    - If you adjust the angle try to get back soundstage and bass, for example 80 degree horizontally. You will lost the reflection factor rapidly. But yes you still have the effect of soundstage position shift.
    - Very weird separation and positioning on my ears, not totally bad. Vocal on my face, some instrument next after, or far away, far behind, or anywhere...It's a mixture of very close and very far. It sounds quite fun and special. If other material was used and have a fine tune, this may becomes a positive effect.

    Because the special nature of this reflector, especially it decrease and sharpen the bass seriously. I can't accept to apply this on my BASS+WIDE cans(Open Alpha).
    If I have another stock Fostex on the future, I may use this reflector to mod a Meditation/New Age/Trippy cans.
    Last edited: Aug 21, 2018
    Light - Man and rendyG like this.
  12. Light - Man
    @Artyouth Interesting stuff!

    I suppose a lot will depend on what material you use. I would imagine that a hard plastic card or metal would reflect the sound differently. I think that it could be a bit of a mine field as the material and design will have different characteristics of reflection and absorption and will also vary at different frequencies.

    Do you know where we can get the longer screws needed for the comfort straps?

    Can you buy Mk3 baffle plates and pads for your Mk2?

    I would imagine that it might be easier for you to buy a new Mk3 headphone because I reckon that you will save a load of time and effort modding the Mk3, which I am enjoying more that the Fostex T60.

    I am beginning to get places with my easy to do mods and I will post them within the next week or so.
    Last edited: Aug 26, 2018
  13. Artyouth
    I'm now working on a fully open(without cup) experiment. This angled reflector may apply on it let see.

    Sorry I was just found some similar size screws in my tools box. As I know the plastic parts of the join is quite soft and will not split easy. Use a little thicker and longer screws also ok.

    Can't wait to see your easy mods.
    Light - Man likes this.
  14. Light - Man
    Thanks anyway, I will have a look around to see if I can find some suitable screws. Like you say, the plastic pieces with the threads are fairly flimsy and could be easily broken or cracked, so we need to be careful.

    I reckon that you will be disappointed with my mods as they will just apply to the Mk3 baffle plate (and pads), which you do not have. :smile_phones:
    Last edited: Aug 26, 2018
  15. Artyouth
    They will not crack easy believe me. My first try used a quite thick and too long screw, it almost come through the cap surface to creat a “bulge“ then I noted that's too long. It's not a brittle kind of plastic (Mk2).

    Actually I have a semi-Mk3 baffle. Which is an Open Alpha baffle with pad ring. And I modify it to have 3 baffle vents(2cm width).
    Last edited: Aug 26, 2018
    Light - Man likes this.

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