SBAF HD800 Mod Impressions and Permutations

Discussion in 'Modifications and Tweaks' started by OJneg, Jan 17, 2016.

  1. OJneg

    OJneg The Most Insufferable

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    All art, instructions, material selections and information in this post and following posts (collectively the "SuperBAF HD800 Community mods") are covered by the Creative Commons Attribution-Sharealike 4.0 international license. Any derivative work may be sold as long as instructions and art are distributed freely and correct attribution (mention of the name of the mods, SuperBAF, and a link to this thread) is maintained.

    So I got my HD800 back yesterday with the SBAF mod outlined here. As is, it is an excellent improvement over the current swath of mods and I find myself able to listen to the HD800 with ease. It is very much comparable to the Anax 3.0 mod, and I find the new organic material that @zerodeefex picked out to be better at doing its job. I do plan on attempting to add/change a few areas based on what I've played with in the past and what others (who have not published their mods) have suggested. This will be a more methodical approach (both by measurement and by ear) to headphone modifications that seeks to isolate each specific tweak and quantify its effect, and ultimately find a combination that gives the best result. I expect this will be an ongoing process.

    Coming from dead stock let's list and review all the things we can change:
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    Dust cover: Take it out. It sounds worse
    ---
    Absorber: We first saw people using the shelf liner in the Anax 2.0 mod in an attempt to cure the extra reflections that would be bouncing around the silver screen that makes up the HD800's large enclosure. The silver screen is necessary to maintain our bass response, but it creates the diffuse treble effect. At this point, the thicker absorber shown in the SBAF mod v1 is an excellent choice. Its effect is seen as reducing the 1k-4k depression which makes this overall sound more even. It does not, however, do much to counter the 6k peak, although it might play a part in reducing treble energy above that region.
    ---
    Resonator: This refers to any sort of tubing you might choose to place inside center of the HD800's driver. As of now, there is the z28 Resonator and Dupont Resonator that aim replicate the same HD800S design trait. As we learn more about what the HD800S is actually doing, we can try different materials and geometries in this position. The resonator mod directly effects the 6k peak and might be our strongest tool to combat it
    ---
    Ring: This refers to the metal ring that sits around the HD800 driver. The original HD800 mods aimed to place damping material here. Now that we (presumably) have a larger "absorber" that overlaps the metal ring region, any additional damping on the ring might have questionable effect. I will attempt to unravel if there needs to be a material here
    ---
    Trapezoid: This refers to the black plastic region that lies over what is the connector housing inside the cup. The question here is similar to the ring one in that now we have an absorber covering it, it is of questionable effect.
     
    Last edited: Feb 1, 2016

  2. OJneg

    OJneg The Most Insufferable

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    Note on HD800 measurements:

    The HD800 can be difficult to measure because of the positioning with respect to the mic and the fact that the response will change drastically based on what material you are coupling it to. We could delve into which measurement technique delivers the most accurate representation of reality, but that's best left for another thread. The bottom line is I find a lossy coupler (open cell foam) to be the most revealing of modifications taking place, and the most indicative of what I hear when I put the thing on my head. Mic here is a WM61A with a phantom power cascode preamp, although I get very much the same results with a omni wand mic that many others use. Open cell foam also means that the bass response below 500Hz or so will roll-off so you I can't really judge any changes there. To my ear, none of HD800 modifications really change the bass response although they can alter apparent midrange warmth.

    The Cork Mod:

    corkmod.jpg

    Inspired by both @Besnia and @SKiring I've added a new modding material to my arsenal, pressed cork rolls. I got a large roll from BedBathandBeyond for a good price. It has an adhesive backing which makes installing easy. Removing is also non-destructive so long as you're careful to peel off the adhesive backing. The cork does have a tendency to flake off if you try to fold it hard. The geometry is the same as the original HD800 mods (I used Tyll's cutout) with both the ring and the trapezoid. So far I've tested both independently and the effect of both elements is solid.

    The SBAF Absorber in Effect:

    Here's a look at the HD800 with and without the SBAF absorber in place. In this case, the cork mod (ring + trap) was applied to both:

    With and without SBAF absorber.png
    And that's pretty much how I hear it. I did try a listening session with the Cork Mod alone and it's just over the edge in terms of treble bite.

    Note how I said before that the absorber does not affect the 6k peak. Strickly speaking it doesn't but rather brings up the upper mids and smoothes out the 4-6k slope. It only looks like it does here because I've matched the plots at 1k. Either way, the sum of the effect is what we want to see.

    So now that we've verified that our new absorber is quite effective, this is what we're going to play off going forward.

    sbaf+cork.jpg

    With the absorber firmly in place, we need to know if the ring and trap mods are worth bothering with. The absorber covers both parts of the headphone so you might presume that damping is not needed. Not the case though, as both trapezoid and ring seem to still make a difference to my ear. The ring making the largest (and most measurable difference) to my ear:

    SBAF Absrbr + foamtrap with_without cork ring.png
    Extra damping around the ring does bring down the treble enough to make a difference (note scale). In addition to the treble reduction, I also feel the ring adds a certain warmth to the mids. The foam ring seemed to add too much warmth with the absorber mod, so I always took that out. But with this new cork ring, I feel it's doing just enough work here.

    With regard to the trapezoid, I feel that the difference between the foam and cork is neglible once you have the absorber installed. But the trapezoid still makes a difference here, and all I can say is that I prefer the cork trapezoid. There is no measurable difference I'm seeing however, so I'm going to test a few other trapezoid materials and maybe try some CSDs to see what they reveal.
     
    Last edited: Jan 21, 2016
  3. OJneg

    OJneg The Most Insufferable

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    Reserved
     
  4. zerodeefex

    zerodeefex Unpaid LH Labs volunteer - Admin

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    Strongly suspect the final mods will be:

    Absorber
    Resonator
    Optional trapezoid for especially treble sensitive folks

    Very excited by what you're doing here.
     
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  5. OJneg

    OJneg The Most Insufferable

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    Mind reader :confused:
     
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  6. EraserXIV

    EraserXIV Friend

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    Hm...

    I think what's most fascinating about this approach is you start with a "clean slate" and can adjust it to you own tastes with the mods (and to varying degrees within each mod)..

    Whereas the HD800S already has something done that can't be undone (well I guess you could undo the resonator but that defeats the whole point)
     
    Last edited: Jan 22, 2016
  7. OJneg

    OJneg The Most Insufferable

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    2nd post updated.
     
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  8. zerodeefex

    zerodeefex Unpaid LH Labs volunteer - Admin

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    THANK YOU! This is awesome to see what's happening with the different mods.
     
  9. evanft

    evanft Acquaintance

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  10. OJneg

    OJneg The Most Insufferable

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  11. thebigbug

    thebigbug Rando

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    Have you made any changes to your mod setup in the past few months? Or do you think you're going to stick with what you've shown in the 2nd post?
     
  12. Besnia

    Besnia Acquaintance

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    @OJneg , I see your enthusiasm has waned, so I feel obliged to reinvigorate it :)

    Here's some food for thought for the daring folks... get rid of the protector in front of the driver. Cover half of the driver ring with something rigid, like a plastic sheet or a very stiff cardboard. The idea behind this is that the driver is too close to the ear and waves don't have time/space to integrate like on a speaker (cancel, amplify or anything in between). Since the HD800 driver doesn't have a dome, which is very good, you don't have to cover exactly 50% of the surface. Start with 30% and go to 70% to see how the sound changes. Don't go too far though, the more you cover of the fold (where the coil is attached to the membrane), the less treble you'll have. Also, the sheet doesn't necessarily have to be rigid. If it's rigid, you won't be losing energy, but if the mids and lower treble come out too much, slap something gummy (like dynamat) on the inner face of the sheet, facing the driver. It will absorb a lot of energy, will sound more transparent, but the sound signature may become more distant, so to speak.

    Enjoy!
     
    Last edited: Nov 15, 2016
  13. Priidik

    Priidik Friend

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    Interesting idea.
    Although I have understood that such approach manipulates acoustic impedance wrt wavelength. Giving easier time for bass vs highs in this case.
     
  14. Besnia

    Besnia Acquaintance

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    Yep. It's essentially a front loaded enclosure. Basically you'll have a semi-open enclosure within the enclosure, the cup. However, the vent is too large relative to the volume of air between the sheet and the cone, so it will have no detrimental effect on sound, other than a slight lift in mid to low frequencies. And this can be corrected (if necessary at all) by applying some absorption right in front of the covered part of the driver cone. There are various ways in which you can adjust tonal balance, and the guys on this forum have done tremendous job with mods. The goal with the suggestions I propsed is to reduce the effective area of the transducer.
     
  15. Priidik

    Priidik Friend

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    Ok I tried cork as cover. Didn't work as intended for me. This does not automatically discard the potential ofc.
    When I covered the whole driver the cork seems to have rather unique absorbing characteristics, it does let bass through.., and highs at some bands. [​IMG] [​IMG]
     
    Last edited: Nov 15, 2016
  16. Besnia

    Besnia Acquaintance

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    Cork didn't work for me either, regardless of the thickness. It makes the frequency response weird and the overall sound unfocused. Cork absorbs to some extent mids and highs, but it's also porous and acts as a diffusor. I love using it to tackle baffle diffraction, but it doesn't work well in this application. I've also tried rubberized cork (rubber + cork mixture) and it's better. I'm using some compressed cardboard sheet that's soaked in bakelite resin. It's almost as rigid as plastic, but easier to cut. Also, the sheet needs to be as close to the driver membrane as possible. I sold the HD800 quite some time ago, but I'll take a photo of my HD650 later to show you what I've done.
     
  17. Besnia

    Besnia Acquaintance

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    Take a look at this. The sheet covers exactly 50% of the driver area.

    [​IMG]
     

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