ETA Genesis G Modding Guide

Discussion in 'Modifications and Tweaks' started by E_Schaaf, Aug 17, 2021.

  1. E_Schaaf

    E_Schaaf MOT: E.T.A Headphones

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    This thread is meant to be an exhaustive compendium for tuning your ETA Genesis Graphene v1.1 with the included tuning kit. I hope this post provides insight regarding how simple it is to tweak these headphones to a wide scope of tastes. I’ll be diving into this using pictures and frequency response measurements. I’ll make the broadest sonic strokes first and then narrow in on the more subtle tweaks.

    Note that several of the options I'll mention later do not make a difference in measured frequency response but still may have a significant subjective effect. I will leave the pad rolling to another post - every measurement here is taken with stock Gen 1.1 sheepskin pads. I am using MiniDSP EARS with an older SBAF comp curve (not sure where to find the latest). I'll post all measurements with 50dB of range on the y-axis so we can get a close look at what's going on.

    First a measurement of a stock GenG v1.1 (white line), overlaid with a stock HD650 for reference (red line below):

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    Next, we’ll start barebones - no front foam on the GenG and no cotton rolls on the back of the driver - just the stock felt patch over the driver’s magnet vent (I don’t suggest taking off unless you have your own felt to replace it). Pads still on.

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    This reflects the white line, vs stock in red.

    [​IMG]

    You’ll see that the bass rolls off quickly, which is indicative of the frontwave freely escaping the shell through the substantial degree of venting surrounding the front of the driver area. This is the first thing to fix.

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    Pick your poison, blue foam (red line below) or white foam (white line below). White foam has a higher acoustic impedance, hence it traps more pressure in the ear cavity thus producing a greater amount of bass. Blue foam provides the minimum amount of acoustic impedance required to get satisfactory extension in the bottom end for my target. The orange line below indicates what is added when switching from blue foam to white. There are still no cotton rolls in the back:

    [​IMG]

    Despite a somewhat reasonable/listenable tone, with completely open venting on the rear of the driver the imaging can become a bit blurry and the decay can become indistinct and/or glaring. A very large portion of dynamic drivers on the market ship with the edge vents 82-100% covered, generally with paper-like materials of high acoustic impedance.

    ((Sidenote: if you’ve ever mic’d a guitar/bass amp, you likely know the trick about how if you point your mic closer to the edge of the speaker cone, you’ll pick up more 'presence' and 'crunch'. Similar principles apply here - reinforcing the rear edges of the driver pushes more of that energy forward towards the ear instead of allowing it to escape out of the back of the shell.))
     
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  2. E_Schaaf

    E_Schaaf MOT: E.T.A Headphones

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    ((Sidenote: the cotton rolls are a temporary compromise for blockage material because they are easy to cut and shape with a good range of coverage. They impede about as much airflow as the paper materials used in many stock dynamic drivers without exciting any resonances or reflections inside the driver frame. A more semi-permanent and decent-looking solution is black micropore tape. Our longer term plan is to start printing permanent fixtures inside the shells themselves that will render most of this thread redundant while also allowing the same type of control during production, without the need for the 'soft materials'.))

    Let's see how blocking off some of the vents using the cotton rolls can work with blue and white foam:

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    Blue foam - white line is 1 roll used (8 vents open); red line is all vents open, orange is the difference when adding the roll(s):

    [​IMG]

    Blue foam - white line is 2 rolls used (3 vents open), red line is all vents open, orange is the difference when adding the roll(s):

    [​IMG]

    (^^^this is what you'd get if you swapped white foam for blue while changing nothing else about the stock headphone)

    Blue foam - white line is 3 rolls used (0 vents open), red line is all vents open, orange is the difference when adding the roll(s):

    [​IMG]

    White foam - white line is 1 roll used (8 vents open), red line is all vents open, orange is the difference when adding the roll(s):

    [​IMG]

    White foam - white line is 2 rolls used (3 vents open like stock), red line is all vents open, orange is the difference when adding the roll(s):

    [​IMG]

    White foam - white line is 3 rolls used (0 vents open), red line is all vents open, orange is the difference when adding the roll(s):

    [​IMG]

    For me, the sweet spot here is 2-4 vents open with the white/yellow foam, or 4-7 open with blue foam. Stock is 3 open with white foam. I don't feel that these measurements are perfectly indicative of the sound that you get because ear placement is quite important with asymmetrical driver treatments like this - especially in the 2khz-4khz area. There's an element of frequency-variable diffusion at play that is hard to visualize with EARS FR alone. Keep in mind it's possible to achieve an 'in between' response by cutting the cotton rolls in half for half coverage.

    Once you’ve settled on how many driver vents are open, the next consideration is which vents are open. This is where we step into subjectivity and user variation with diminishing returns in frequency response measurements. I find it helpful to think of the vent placement as a type of imaging and transient control, and imagine how the vents line up to the anatomy and placement of your pinnae within the earpads.

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    To me, I have a subjective sense that my ear ‘catches’ the most LF sustain closest to the concha, with the cymba (the upper part of the concha that doesn't directly feed into the ear canal) and scapha being more sensitive to higher frequencies and sharpness of transients. Thus, I leave the topmost vent open and at least one vent open closest to the bottom of the driver by the solder pads. For me, this provides the most balanced sense of bass reinforcement and imaging clarity without aggravating any sense of transient overshoot or bloat - the middle path. If you want more sustain in the lows, leave the bottom-most vents open. If you want more sharpness, cover them up. The vents about halfway up make a more subtle difference than the ones closest to top and bottom. YMMV.
     
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  3. E_Schaaf

    E_Schaaf MOT: E.T.A Headphones

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    Shell vent plugs offer another tweak that doesn’t make much difference to measured FR unless you go totally wild with them (as in, plugging the majority of the vents on the outside of the shell). The vent plugs are somewhat like the baffle foam in that they control how much pressure is trapped on the front side of the driver. However, it is more subtle in this case - the plugs are more of a decay adjustment than a tonal adjustment. Most of the effect will be perceived in the upper-bass / lower midrange; the more plugs, the more bloom and decay you’ll get. The plugs that will make the most difference are directly at the top and bottom of the shells, but in this case that’s most likely because those vents are the ones that have the most direct pathway to the ear given the shape of the earpad cavity.

    With the white foam, most listeners so far have preferred 0 plugs, with a few listeners preferring 3-4. With the blue foam the range of preference is a bit wider, with some using as many as 11 plugs per shell.

    The last subtle tweak is to adjust how the pads are angled on the headphone - thick side up or thick side down.

    [​IMG]

    Thick side up positions the bottom portion of the driver closer to the ear and mimics how most people's pinnae are slightly more protruding towards the top than the bottom. This positions the driver in an uptilt towards your ears, more direclty on-axis with the plane of the pinna itself. For me, it presents a clearer, more cohesive midrange. Thick side down can give a little bit more kick in the bass and give images a bit more depth. Be mindful not to break foam seal when rotating pads or you'll lose all your bass.

    That's all I've got for now! Feel free to ask 'what happens if'-type questions, I can replicate and measure anything requested. Pad rolling is next.

    Thanks for reading and happy modding :)
     
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