"Open Alpha" DIY project from MrSpeakers

Discussion in 'Headphones' started by Pyruvate, Nov 18, 2016.

  1. Baten

    Baten Friend

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    That capture looks really nice spoony. Good work :O
     
    • Agreed, ditto, +1 Agreed, ditto, +1 x 2
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  2. spoony

    spoony Spooky

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    Thanks! There's still a few things I'd like to improve upon but time has been scarce:
    • Better sub-bass extension
    • Remove a bit of glare that remains at ~6-8 KHz
    • Midrange distortion (maybe this is driver-specific and there's better samples out there)
    Things I'm not sure can be fixed here:
    • Slight macrodynamic compression
    • Slight lack of microdynamic nuance (plankton)
    That said, there's still a bunch of things I very much enjoy about this headphone:
    • Deep 'blackground'
    • Clean decay and fast midrange transients
    • Images come from everywhere and 'float around' in a way I enjoy
    • Decent clarity
    Hope some of this will be useful to people messing with these cans, they're a lot of fun.
     
    Last edited: Jan 25, 2023
  3. Biodegraded

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    What amp(s) are you using with them? Recent experience has me thinking the Tx0RPs are significantly harder to drive than their specs would suggest, perhaps more so than other planars with impedances in the same order. @purr1n has mentioned this elsewhere too.
     
    Last edited: Jan 25, 2023
  4. spoony

    spoony Spooky

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    Jot2 @ high gain, single ended. Previously Vali 2 @ high gain. They 'woke up' with the extra juice when I first got the Jot2, I've still to be arsed to convert them to balanced to get more juice out of the amp. This is a relative measure to the high-efficiency dynamic drivers I got installed in my other headphones, perhaps an unfair comparison.
     
  5. Philimon

    Philimon Friend

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    T20RP driver baffle and stock under pad vent foam, stock flat pads.
    Im no expert obviously so cant make any inferences about cup or driver resonances or quality of measurements. fwiw:
    [​IMG]

    [​IMG]

    T20RP micropore VS T20RP butt naked.jpg
    T20RP driver CSD.jpg
    T20RP driver micropore CSD.jpg
    T20RP paper removed CSD.jpg
     
  6. BearFacts

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    The issue that I am struggling with on my open alphas is they sound very dark and seem to lack clarity, even compared with my T50RPs that include a mayflower-like mod (similar mod using materials that I had on hand). I currently have the cups lined with paxmate, two layers of loose wool roving, paper still on the back of the driver but with a 12 mm X 10 mm patch of stiff felt stuck on. Using 1 mm wool felt on the ear side of the baffle. The patch of stiff felt brought more sparkle, but still pretty veiled sounding headphones. All holes are open....closed 2 or 3 but didn't seem to make much difference. Baffle sealed to the cups with caulking and pads are alpha dogs.
     
  7. spoony

    spoony Spooky

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    I've had mixed results using ear-side filters, most of the time I get agreeable treble level but blunted transients and indistinct imaging, that's why I favor pad rolling before ear side damping. As an exercise, try removing any front damping from all your pairs and A / B, plus points if you can switch the pads between them too. General darkness could be due to a scooped presence region which is fixed with direct damping of the driver's back side, that's why I use the cosmetic pads, they raise 2-5 KHz.
     
  8. spoony

    spoony Spooky

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    This is great, shows that the scooped presence region is not the result of a destructive interaction with closed cups, and probably has more to do with diaphragm damping, as shown: more damping = less scoop. The trick lies then in achieving a good FR balance without killing dynamics or producing other undesirable effects.

    BTW: I also found that achieving a flat or level-measuring presence region in a flat-plate coupler led to kinda hot upper mids with this driver to my ears, I balance that region by ear and using other headphones as reference.
     
  9. Philimon

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    And that’s where it gets tricky. I like modding headphones because theyre like a puzzle game. But I get impatient and stumped pretty easily so Im ready for the solution now. Ill try my best to copy you (and company from mk3 thread), thanks. I should probably start by getting new pads.
     
  10. BearFacts

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    Thanks. I probably wasn't clear - I have a square cut in the wool felt the same size as the driver, so the wool felt on the ear side isn't filtering. In any case, I'll do a bit of pad rolling to see how that works out....have some shallow pleather and thick velour pads that I can try.
     
  11. spoony

    spoony Spooky

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    Most of the fun is in the journey ;)
    FWIW: Not claiming that my mod is better than anyone's, it's worked for me and it's probably worth a try to see if any of the tricks I used are down your alley (preferences and all), but it's likely you'll arrive at a different place when you are happy with the results.

    I'd remove anything that covers the front when making judgement calls about clarity or doing A/B comparisons. I used to have one or more 'doggie treats' installed with certain deep pads, but then found out that a pair I had just started modding sounded clearer than my extensively modded pair and it was down to the front obstructions, when I removed the dots the clarity was leveled but of course I now had hot, spiky treble due to the pad choice.
     
  12. BearFacts

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    Good call on ear side materials impacting clarity. I removed the 1mm wool felt with the driver size hole cut in it and clarity improved immensely. With just the plastic surface of the baffle, there was too much sibilance/sparkle, so I just put some card stock with a hole cut out for the driver in there and that tamed things quite a bit. I wouldn't have thought that a gram of 1mm thick felt around the driver would impact things as much as it did.

    I also tried velour pads and some shallow pads. Although I'm not a basshead, the velour killed the bass a bit too much, and the shallow pads did not sound as full as the deeper, angled alpha dog pads, so I'll stick with this configuration for now.

    Thanks again for the good advice.
     
  13. Philimon

    Philimon Friend

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    Flipping between denser Dekoni Blue foam and T20RP foam, I keep coming to the same conclusion that I prefer the lighter density under pad vent foam. Removes overdone* bass bloom. Drawback is bass roll off.

    Not sure the common use of bass "bloom", but I use it to refer to a feeling of pressurization (literal physical pressure upon ear drums which results in fatigue) and slow bass release. *I think bloom can be used in moderation to compensate for limp sounding bass.

    Going on a tangent, but I think (guessing) bass reverb from pads can be used to effect as well. For example, velour pads and perforated pads can be of seemingly equivalent acoustic impedance value but cause different perceptions on bass. ime Velour pads tend to sound less impactful vs their leather perforated versions despite frequency response measurements being very similar. I think open back vs closed back (headphone cups) have similar effects on bass perception due to reverb as well.
     
  14. Philimon

    Philimon Friend

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    I plan to attempt sbaf mk3 thread driver damping mods (e.g. @spoony) and will update with results later. I also want to try a couple new pads. One such pad being the ZMF Oval pad designed for T50RP. But as I added the pads and a new headband to my cart I realized that the upcoming ZMF woody T50RP might already come with those extras so I sent an email to ask to save myself from duplicate orders. Will update with response unless @zach915m wants to post himself.
    [​IMG]

    edit: ZMF said they plan to release woody T50 kit in Spring. No other details.
     
    Last edited: Feb 6, 2023
  15. Philimon

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    Returning to original full-version Open Alpha for one last experiment to prove that back of driver damping helps with flattening frequency response. What I did was place micropore tape on back of driver.:
    Open Alpha full version mod2.jpg
    ^ EARS
    Like @spoony mentioned earlier, shallower pads would help with reducing highs @ 8kHz. I am using Dekoni leathers which are not angled and on the thicker side. "mod2" improved overall on tone but a bit sibilant due to 8kHz. I'd have to listen side by side with my hybrid version to make any confident judgements on technical abilities.

    Last experiment on full-version because Im deconstructing to turn this OA into another hybrid as I prefer the mk3 baffle venting system...
     
  16. Philimon

    Philimon Friend

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    [​IMG]
    I think I had accidentally switched to Dekoni Blue pad vent foam for prior T20RP measurements (sans damping). Will modify effected post(s). Will buy another T20RP to verify.
     
    Last edited: Feb 12, 2023
  17. Philimon

    Philimon Friend

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    Bass BLOOM: overly long release of bass that is usually caused by lack of venting and often causes headaches or ear fatigue.

    - T20RP under pad vent foam is light density and allows air pressure to escape easily.
    - Dekoni Blue under pad vent foam is high density and doesnt allow air pressure to escape easily.

    FPC and dekoni leather pads:
    T20RP dekoni blue foam VS T20RP stock t20rp foam.jpg

    T2ORP t20rp foam CSD.jpg

    T20RP dekoni blue foam CSD.jpg

    I think these CSDs are showing the difference bass bloom that I hear.

    The Open Alpha mod doesn't have any front-side venting which is why I chose to go hybrid by combining with mk3 driver baffles that use under pad venting.
     
  18. JK47

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  19. Philimon

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    For comparison, Open Alpha (full-kit version) CSD:
    Open Alpha CSD.jpg
    ^ this is using the same pads as last post (Dekoni leather) measurements of OA-h and T20RP.
     
  20. Philimon

    Philimon Friend

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    T20RP (dekoni blue foam aka dbf) versus T20RP (dbf) but with most of the back-side cup vents sealed:
    T20RP (dbf) VS T20RP (dbf) most cup vents sealed.jpg

    Now compare T20RP with most cup vents sealed against OA-h (dbf):
    T20RP (dbf) most cup vents sealed VS OA-h (dbf).jpg

    Open Alpha 3DP cups vents are optimized for linear bass-mids response when using zero front-side venting per design as seen here. In hybrid configuration I bet if I drilled an extra hole or two into cups I'd get more bass (like stock T20RP cups).

    edit: A thing I forgot to mention about venting (front or back). The higher acoustic impedance the higher the driver control which results in improved microdynamics, distortion, and CSD in some ways. However, transient behavior is not always all improved. If driver is put on too much of a leash you lose on bass macrodynamics, and may blunt or round note decay unnaturally. *in my limited experience
     
    Last edited: Feb 20, 2023

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