TH900 mod extravaganza (stream of consciousness)

Discussion in 'Modifications and Tweaks' started by E_Schaaf, Jun 16, 2020.

  1. E_Schaaf

    E_Schaaf MOT: Upscale Audio; recovering HFM addict

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    Figured it might be time to post about what I've been doing with the TH900. I've tried about a million things with these, and the pictures I'm going to post are pretty much the best I could get them before I decided to use wood glue to permanently screw the cups in place. Not because they're perfect, but because I had already crossed the line into insanity and needed to preserve my own mental health. The tuning I arrived at was as close to perfect as I could get for my tastes and given these headphone's strengths. No, they'll never have the imaging of some open headphones, and they'll never be dead flat. But for tactility and slam with a fun tuning that still reveals mixing choices and recording differences with ease, I haven't found better. Lets just say this is the headphone that is making my 3 pairs of HE6 sit and collect dust.

    When I first heard the stock 900s, I was mortified. Sharp lower and upper treble, fucked mids, bass completely separate from the rest of the response. Yuck. I had already heard the X00s and knew the 900s were built in almost the exact same way save for the pads, so I knew there was potential (turns out the X00s have ZERO cup damping stock, whereas the 900s are stuffed with some type of loose acoustic fluff).

    Anyway, I started my journey many months ago and am now fairly close to calling it quits - I'm just doing pad rolling for the most part now. Along the way I learned a lot of functional knowledge and have a feel for what little tweaks could be made to change things like the degree of the cup effect, the localization and amplitude of the bass boost, the general slope of the response, the degree of the BBC dip, things like that. This headphone is actually a great modding platform for experimentation - fairly easy to take apart (4-8 small screws per cup depending on what you're trying to do), and every change makes a measurable, perceptible difference.

    I've experimented with over 40 materials in every sensible arrangement - front of driver, magnet assembly, front and back of baffle, cup inside, cup outside, pad mounting ring, pads, headband, the list goes on and on. I've even experimented with some irreversible things too, like tearing off the paper damping on the rear of the driver. You'll see -

    Cups:

    Bottom layer -
    [​IMG]
    Dynamat-like goop around the outermost portion of the cup perimeter, covered by adhesive felt, rug liner in the deepest flat portion under the cup surrounded by small cuts of dense crafting foam with more adhesive felt. The felt covers around 60% of the bottom of the cup as you can see. This felt doesn't deaden the cup effect in the bass and lower mids, but it does eliminate internal treble reflections and helped to smoothen the treble quite a bit.

    Second layer -
    [​IMG]
    More adhesive felt around the top portion of the cup. Dense foam nubs around screwholes were later removed, but further experimentation here will be done. Circular covering of memory foam taken from the inside of a headphone pad and cut to shape (varies in thickness / sloped). The shallower parts of the foam were covered in fairly densely packed cotton, cut from dental gum swabs. I know this looks like an assload of damping, but the rear portion is still bare wood under the rug liner, and the memory foam actually breathes quite a bit. Basically the rear hole on the driver assembly is the only thing that fires through the whole cup depth, the secondary driver damping fires into the cotton/foam blend. This helps to lessen the degree of the BBC dip (though it's still definitely there), though not kill off too much of the cup effect. Took a LOT of experimentation to get here.

    Driver/Baffle Rear:
    [​IMG]
    Removed all paper damping on driver assembly (kept baffle paper). Micropore'd selectively for symmetrical half covering. Dynamat-like goop applied to top and sides of all non-obstructive parts of the assembly. Plugged baffle port with foam and micropore tape (this fixes the lower mid dip but also traps a lot of energy in the cups, was later removed when I settled on a pair of pads the alleviated the dip without this mod). I've tried stuffing all the driver holes with all sorts of materials but this option gives the most freedom of motion for the driver - once you do this, you have a lot more control over the dynamic presentation because whatever you do with the cups has a much greater effect. I did use foam to plug the open cavity where the cable ran through the baffle. On other pairs this is hot-glued shut at the factory. Even with all my cup damping, you can physically feel mechanical conduction in the cups as the music is playing with the reduced amount of driver damping. Addictive.

    Pad mounting ring:
    [​IMG]
    This ring actually sits in front of the outer portion of the front baffle, so damping here does make a difference. I added dynamat-like goop and also a layer of adhesive felt (not pictured). This covering made the pad mounting mechanism obsolete, so I now use double-stick tape for all of my pads.

    Exterior:
    [​IMG]
    Dense foam applied with about 70% covering. This has MUCH less effect than the same amount of foam applied to the inside, since you're not affecting cup dimensions. But it does help to tighten things up a bit. Could go without this with a different internal scheme. Notice the foam that couples the top of the cup to the headband - this makes it possible to adjust the degree of the cups relative to the ears in a fixed way, which is helpful to maintain a perfect seal and comfort when on the head. It also helps conduct some of the cup resonance to the headband (I can feel the headband gently vibrating with my finger as music is playing) - jury's still out on whether or not this is a perceptible or important difference, but to me, it adds tactility in the bass while also reducing boom.

    Final FR with zero front damping (aside from stock foam that sits around the driver on the front of the baffle) and AP2000Ti pads (my favorite on these, really a random find, and honestly they are a little too small). I stretched them a bit to fit onto some plastic rings and taped them down, but there's still about 1-2mm of extra space around the pads. Doesn't bother me - looks a little jank, but IDGAF when they sound right to me. EARS and SBAF comp curve - modeled after Marv's -

    [​IMG]

    Don't mind the bumps in the bass - just my noisy AC unit. Haven't changed my comp since all the measurements on this thread ( https://www.superbestaudiofriends.o...easurement-dump-zmf-focal-audeze-extras.8087/ ) so you can use that for reference. This graph's got 5dB scales though, hopefully that's easier to read. Happy to post measurements with different scales or pads or damping or whatever. 10dB dip at 3k looks like a lot, I know, but considering the general slope it's probably closer to 3-4dB below what I'd consider my target. Some pads help with this, but bring other issues. I've tried about 20 pairs. If only I could open them up one last time... but I won't go there. EARS isn't great with CSDs or I'd post those too. Need to figure out how to do accurate distortion measurements...

    EDIT - A couple runner-up pad combos (both with 2-ply TP front filter, which isn't needed with the AP2kTi pads, and treble-tolerant people like @brencho could probably do without TP on these too). I'm super sensitive to any amount of treble accentuation, which is why I never let the FR in the highs supersede amplitude at 1k. Same comp as above, but different dB scales on the Y-axis. Can fix this later.

    Stock TH900 pads -
    [​IMG]

    Brainwavz XL Lambskin -
    [​IMG]

    Modded HD6XX (posted about in the 650 thread - kind of like KISS mod)
    [​IMG]

    Going forward, I have a pair of X00's I'm going to keep messing with indefinitely. Feel free to ask questions like 'what happens if...' - chances are I've already tried it, or if not, I'll do it and provide measurements here. There are at least a few dozen things I've tried that I haven't mentioned above. This is the best I've been able to do so far. Hopefully I can get some more impressions soon!
     
    Last edited: Jun 16, 2020
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  2. Armaegis

    Armaegis Friend

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    Something I've always wanted to try... affix a right and left hand threaded rod with a coupling nut inside the cup, so you can adjust the tension/compression in the cup and see how that affects resonance.
     
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  3. Serious

    Serious Inquisitive Frequency Response Plot

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    Looks like a ton of experimentation. Impressive how you can get the treble so linear. I'm sure the complex back damping has a lot to do with that, doesn't it? Does the orientation of your second layer make a noticeable difference? Also which types of felt did you try for back damping? Looks like polyester felt to me, but I could be wrong.
     
  4. spoony

    spoony Spooky

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    Somewhere in Japan there is a lacquer craftsman contemplating seppuku.
     
  5. Grattle

    Grattle Friend

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    Makes me cry a little to see that. Those poor TH900's. Reminds me of this:

    upload_2020-6-17_10-52-46.jpeg
     
  6. E_Schaaf

    E_Schaaf MOT: Upscale Audio; recovering HFM addict

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    Alright, I'll admit I show no regard for the cosmetics of my own gear when I'm deep into tweaking. Of course if anyone wants me to mod their pair, they'll get a cleaner result since I'll just go in and apply everything correctly the first time (and I can find a workaround for all the exterior tweaks). I do cut everything by hand though - takes a long ass time and will never quite be perfect.

    @Serious it is polyester felt. Cotton or wool would likely be better but I ran out of those doing other mods. There's enough stuff layered on top that it probably would be a minor difference, though using a different felt may alleviate the temptation to use TP with the more open pads. The orientation of the second layer does make a bit of a difference - they're mirror images between cups - and I align the cotton with the baffle port so that it chokes that flow just a little bit (helps with the lower mid dip).

    @Armaegis I've been thinking about that too, I feel like it'd make the biggest difference to be able to adjust tension of the cups against the baffle itself assuming you could do some kind of coupled bracing. I tried using foam nubs around the cup screwholes to effectively soften the coupling when screwed down, but my foam was a bit too thick so I gave up on that idea after it wouldn't fit. Tightening would probably yield a more interesting result than softening (might kinda just be like changing wood hardness on the cups), but that's more mechanically complex than I can accomplish with a pair of scissors and a circular stencil, which is all I really have to work with at home.
     
    Last edited: Jun 17, 2020
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  7. Armaegis

    Armaegis Friend

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    Ah I finally remembered the name... a turnbuckle!
    https://en.wikipedia.org/wiki/Turnbuckle
    or something like the turning bit of a drawing compass

    So if you could get something like that into the cup, possible anchoring two thin threaded rods into the cup itself, then you could adjust by turning the frame or coupler in between them. Hmm this sort of thing would probably be easier to test out on a speaker box first, though I imagine something similar must have been done before.
     
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  8. E_Schaaf

    E_Schaaf MOT: Upscale Audio; recovering HFM addict

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    Very pleased to report that modding the X00 in an identical way yields a very similar result to the 900 in terms of FR (I mean.. it should, the only difference is the magnet) -

    [​IMG]

    Subjectively speaking, the X00 isn't quite as slamming and articulate anywhere in the FR. The highs feel a bit rough despite FR being very similar. Just a bit more... papery? Dry? 1 or 2 ply TP could probably do the trick (no damping with the weird AP2000Ti pads here, just like on the first 900 measurement in this thread above). Then again, I'm kind of like Hands when it comes to treble. I'm just intolerant. This could be fine for most. Quite crisp, especially when compared to a Senn.
     
    Last edited: Jun 17, 2020
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  9. Grattle

    Grattle Friend

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    Reading this makes me regret selling my TH900. I always always regret selling audio gear. Having different things to switch in and out of the chain is half the fun.
     
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  10. spoony

    spoony Spooky

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    That FR profile looks very yummy.
     
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  11. E_Schaaf

    E_Schaaf MOT: Upscale Audio; recovering HFM addict

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    Check this out! X00 with the same mods as the 900, but with a custom triple-layer neoprene front foam (I have a thicker foam on the way so I don't need multiple layers), 2-ply of the lightest TP I have on hand, plus some no-name super plush pads (like seriously these things are thiccccc). I fucking love these pads, they are incredibly soft and lightweight, and because of their dimensions and the way they compress against the head, they seem to help quite a bit with the 3k dip. Pics below. Same pads on the modded ADX5000 I brought to the meet at @ChaChaRealSmooth 's place a while back. @captkirk has those now and doesn't want to give them back, even though I bet I could make them sound better than they do in their present state...

    Here's the FR on the X00 as-is today (matched at 200hz with most of the other graphs above)

    [​IMG]

    Stock X00 for reference -
    [​IMG]

    Not as dramatic a change in FR as with the 900 stock vs modded, but the more open pads help a lot with the sense of space and comfort, the highs are smoother, the mids are fuller, an improved sense of dynamic control, and the whole presentation is generally more cohesive and less W. I'll see what I can do about that 9k dip.

    Pics or it didn't happen -

    This is what my custom neoprene front foam is replacing (stock foam below just for the sake of clarity) -
    [​IMG]

    Front face -
    [​IMG]

    Once the thicker neoprene gets here I'll be able to get that TP more taught against the front of the driver, which should help.

    Pads and foam headband mod (seriously though I like this mod a lot) -
    [​IMG]
     
    Last edited: Jun 18, 2020
  12. spoony

    spoony Spooky

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    Nice work! Do you have a link for the aforementioned pads?
     
  13. E_Schaaf

    E_Schaaf MOT: Upscale Audio; recovering HFM addict

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    Once the thick neoprene gets here I'll do a custom front foam on the 900 and see what that does for the 3k dip there too. I keep going back and forth whether I prefer the dip or not.

    I'm thinking about handing off the X00s to anyone who may be interested in commissioning my mods (of course you can do them yourself given the pics are here, but it does take quite a few hours of labor and you will have to find all the particular materials). I think most would be super happy with the modded X00 as a companion phone to most open backs, or for the slam sluts like myself, the 900. The magnet does make a huge difference. I would send off my 900s, but honestly I don't want to let them go.

    I also have access to a few different types of wood cups without marked branding for those who may want to throw in a bit of extra cash for something really personalized.

    Edit - none of this is through Upscale, by the way. Just a personal passion project :)
     
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  14. OldDude04

    OldDude04 Friend

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    I second that @E_Schaaf, I'd like to snag a pair of those. They look insanely comfortable. Ever so slightly reminds me of the crazy Sony MDR-XB1000 pads.

    HTB1iTsedyjQBKNjSZFnq6y_DpXal.jpg_q50.jpg
     
  15. spoony

    spoony Spooky

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    Cool! However, I don't even own a TH variant, I was mainly interested in the very plush pads you got there for testing with my current mods.

    Edit: Found 'em.
     
    Last edited: Jun 20, 2020
  16. Vordhosbn

    Vordhosbn Acquaintance

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    My TH900's are one of my longest tenured headphones. I pretty much only use them for Electronic and Hip Hop music though. Just have a couple of mods, mostly to tighten up the bass and tame the treble some. I run ZMF Universe sheepskin pads with mine.
     
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  17. Superexchanger

    Superexchanger Friend

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    Any reason to expect this not to work on a Denon D7000? I have a pair I'd be open to have modded. Any ideas on cost for your services?
     
  18. E_Schaaf

    E_Schaaf MOT: Upscale Audio; recovering HFM addict

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    @Superexchanger I see no reason it wouldn't work. Happen to know which Fostex variant the driver for those is equivalent to? Just curious if it's the magnet more like the 900 or the X00. I could probably dig up that info too

    Send me a PM about what kind of tweaks you might want (or just the same as above) with some reference tracks and we can talk about cost. You pretty much have this many options in terms of how you want to balance the FR -

    [​IMG]
     
    Last edited: Jun 22, 2020
  19. tommytakis

    tommytakis Gear Cycler SoCal Edition

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    @E_Schaaf how much are we losing in terms of overall resolve and slam if we choose to use one with weaker magnets compared to the TH900? Do the TH-X00 variants still scale with better source gear?
     
  20. E_Schaaf

    E_Schaaf MOT: Upscale Audio; recovering HFM addict

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    Going from the X00 to the 900 modded in the same exact way, I would say (unfortunately) it's an immediately obvious difference in terms of the dynamic response. I really wanted to believe the X00s could get 99% of the way there (I like cheap), but the stronger magnets do make a really big difference especially when most of the rear driver paper is removed. Very little damping means you need great driver control to get a tight and dynamic sound (ie, strong magnet).

    Given I have a serial number for the 900s, I could probably buy a few pairs of TH900 drivers and do a transplant, but I know Fostex is super tight-fisted with these parts and I want to be sure they won't choke any quantities I may need. Those drivers would cost me about $250 a pair, so it wouldn't be cheap once you add pads and labor and alternative wood cups if you wanted something like that. Might be a lead time too.

    With the X00 modded, I'd confidently say the dynamics are slightly but not radically improved vs stock. Kind of like the difference between a stock Senn and JAR modded Senn. Still a slamming can, and the bass boost helps with macrodynamics, but it probably won't blow your mind dynamics-wise coming from a nice JAR650/Borealis chain. The TH900 might though... ask @brencho (he's got JAR600 and Auteur at home and borrowed my Fostex's over the weekend). The 900 is dramatically more slamming and resolving than the X00 even from low powered devices like the ZX2 or Shanling M0, and scales farther too. The 900 has more gains in dynamic control with the damping removal than the X00 - it likes to breathe a bit.

    I don't want to talk my shit up too much and end up sounding like another modder who does SuperUltimateBestNexxxtGen mystery mod stuff. I just need to get more ears and impressions on these. At the end of the day I tweaked these first and foremost to please myself and satisfy my own tastes - if I didn't think there were worthwhile improvements, none of these posts would have made it to SBAF and I wouldn't have wasted hundreds of hours in R&D.
     
    Last edited: Jun 22, 2020
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