AKG K7xx modding

Discussion in 'Modifications and Tweaks' started by fishski13, Oct 13, 2015.

  1. Works 4 Me

    Works 4 Me Rando

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    I'm not sure if I'm going to join this thread , but I'll pass this info on about the different foam liners that have been pictured here. I've used both the small irregularly "bead" liner & the more uniform sized bead liner on both my HE6 & HD800.

    The smaller irregular sized liner is normally marketed as "shelf liner" really isn't that useful other than as an insert inside of an earpad as a replacement (or I additionally) for what is covering the driver . I used small circles from it inside of the K702 pads I used on my HFM HE6 for awhile , until I decided I prefered some speaker cloth material(similar to the Magnaplanar socks material)

    The other sized foam liner is usually called "rug liner" & I've come across that in 2 different sizes. I believe I found the pictured sized one at a nearby Lowes. This is the one I used inside my HD800 earcups. I'd found another liner that was a bit larger were the foam beads are a bit more elongated & bigger that didn't sit as well to the sides of the cups. (I think I ended up using that one under a small rug)
     

  2. spoony

    spoony Friend

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    So I tested the following materials:

    IMG_20151122_215045074.jpg

    Stock foam, thin rug liner, thicker checkered rug liner, fat anti-slip shower mat.

    Subjectively, the thinner one wasn't very effective. The thicker checkered one works a little better but it doesn't improve imaging in the same extent that the shower mat does for me. I was previously using the shower mat over the stock foam, which interestingly results in the smoothest treble along with a good +1.5 dB boost from 20-1500 Hz

    FR-wise the differences are not exactly dramatic:
    stock.png thin.png checkered.png shower.png foam+shower.png
     
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  3. spoony

    spoony Friend

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    However, the stock pair showed some considerable ringing around 900 Hz in my rig (there's even a dip), but it all became quite clear by means of the spectrogram display:

    stock.png thin.png checkered.png shower.png foam+shower.png

    As you can see, there's quite a bit of residual energy around 900 Hz, which may contribute to the perception of the hazy diffuse sound that I complained about earlier, all of the mats proved to be effective to different degrees. To my ears, the best results were produced by placing the fat shower mat over the stock foam. Some people would prefer the effects of the more popular checkered mat which doesn't impart the 1.5 dB boost to the bass/lower midrange or affect imaging as dramatically.
     
    Last edited: Nov 22, 2015
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  4. jayeshrc

    jayeshrc Resident Crash Test Dummy

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    i tried cutting a piece of cloth (as a ring with a hole in the middle) and added it with the stock foam and it seems to have cut the highs a little and vocals are a lot more level/closer. I need to listen more but so far it does sound a little nicer to my ears.

    EDIT: went back to stock, the soundstage was being sacrificed with the cloth so instead i figured out an EQ setting for the two songs i had the highs issue with
     
    Last edited: Nov 27, 2015
  5. jayeshrc

    jayeshrc Resident Crash Test Dummy

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    has anyone tried the bass port mod? is it reversible? I mean, its just a sticker that needs to go back on, but when you put it back, do you need to add some glue so it goes back with the same amount of stickyness/seal?
     
  6. Friday

    Friday Almost "Made"

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    Tried it, seems reversible and probably doesn't need more glue but I didn't bother trying to put it back on. That said, given the angles you are working with, it will be much harder to stick it back on than removing it without opening up the enclosure completely.
     
  7. Friday

    Friday Almost "Made"

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    I might have found the best dampener for the K7XX: the Valhalla 2. Not sure about output impedance being unsuitable at high gain, but that seems to sound more balanced(?) to me, whereas with low-gain the mids gain more emphasis. Only downside is that it costs 20-50 times more than most dampening materials in SGD. But damn is it smooth (to me at least); I could listen happily without anything in between the earpads and the driver enclosure. And I listen to lots of j-rock and j-pop.

    Note: All previous modding suggestions were based on the K7XX with the Magni.
     
    Last edited: Nov 29, 2015
  8. jayeshrc

    jayeshrc Resident Crash Test Dummy

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    well, if it means ill have more bass impact without really losing overall clarity i'll do it tomorrow. I just dont want something that ends up sounding muffled/veiled. just a bit more bass
     
  9. Friday

    Friday Almost "Made"

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    If that's what you're concerned about then no worries. At least for me, the bass didn't seem to affect clarity much if at all.
     
  10. take

    take Friend

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  11. spoony

    spoony Friend

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    I'd get the Anax 2.0-like rug and one of the thicker ones, so you have more to try. The ones sourced for the HD800 SBAF will probably work better, but they're on the expensive side.
     
  12. take

    take Friend

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    Oh this one, I'll definitely consider that. Thanks spoony!
     
  13. spoony

    spoony Friend

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    Good luck and please share your thoughts ;)
     
  14. Biodegraded

    Biodegraded Acquaintance

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    This thread should probably be allowed to die in peace, but…

    I bought a pair of Chinese-built K702s (SN 133976) about 6 months back for $US ~170. Since obtaining an amp to go with them (Magni 2U), I’ve been doing some listening, (yeah, they’re bright), some mods, and some measurements. I tried a few of the suggestions in this thread, and homed in on @spoony ’s shower mat (posts #62 & 63) and @Marvey ’s toilet paper (post #22).

    TL;DR: 1 Layer of Kleenex, stock foam ring, shower mat.

    Comparative measurements (setup described and compared here) are shown below. I think my rig underrepresents the 7-10 kHz region and overemphasizes the 3-3.5 kHz hole, which are exactly the problem areas with these phones and seem to be the main points of difference between older and newer 7xx models (or maybe individuals), so it’s hard for me to judge how this particular pair correspond to others measured and heard here and elsewhere. Stock, they seem to me obviously too high in the treble but without the artificially wide soundstage or odd effects on guitar distortion that have been ascribed to the 3k hole, which would make them more like 70x versions than 712/7XX - but I can’t claim a lot of experience as a critical listener. The mods, though, seem to do good things to this pair both subjectively (CDs via Magni 2U) and according to the measurements.

    [​IMG]

    All measurements were taken at the same SPL (90 dB, subject to the dubious accuracy of my calibration, at 1 kHZ). With the foam pads removed they measure very close to stock, the main difference being a ~1 dB elevation above ~1.2 kHz. The left-channel hole at 600-800 Hz in the ‘naked’ measurement is I think a positioning artifact, it shows up intermittently. The channel imbalances in the bass and at the 3.5 kHz trough, however, do seem to be real: they persist across all mods and don’t show up on other headphones. Note though that bass response is very position sensitive with these phones on this rig; even leaving them set up for a while changes it, I assume as the pads compress. All these measurements were taken after about the same length of time on the rig, but I didn’t quantify this carefully.

    The toilet paper mod is a single ply of fairly thick (1-ply) paper covering the whole driver, including the centre dome, inserted beneath the stock foam ring as in Marv’s picture. I tried 4 different papers (all underneath the foam): this one, 2 thinner ones from different 2-ply rolls, and Kleenex (thinnest). On listening, all certainly calm the mid & upper treble and don’t seem to do anything untoward to speed or imaging. I could distinguish between the thickest and thinnest but not from one to the next going down the scale. Measured differences between thickest and thinnest – I didn’t measure the intermediates – are 2-3 dB (see screenshots below).

    [​IMG]

    The measurements above suggest they impart a downward tilt to the midrange such that the 2.5 kHz peak is dropped relative to the rest, but that wasn’t obvious to me on listening. Given comments about shower mats and similar items, I wondered if that would warm things up a bit. The mat I used is this one, which I think is identical to spoony’s except in colour; it’s flat on one side and ‘bumpy’ on the other, and I almost wonder if the manufacturer has been reading this thread because the corner radius and the suction-cup centres are perfect fits.

    Using the shower mat over the stock foam reduced the treble, subjectively not as much as the TP, and gave a warmer midrange; and again, technicalities seemed not to suffer. The measurements suggest it reduces mid-treble more than the thick paper but is less effective on the upper treble, doing almost nothing to the big 16 k spike; and that it changes the shape of the upper midrange from concave-up to convex-up, reducing the 2.5k peak and the relief across the 3.5 k hole. It’s interesting to compare with the papers; they give the midrange a tilt, whereas the mat really changes its shape, particularly above 1k.

    [​IMG]

    Lastly I tried combinations: mat with thick paper and with Kleenex (again including the foam ring). The Kleenex was the subjective winner, preserving air and sparkly detail while removing harshness, whereas the thicker paper seemed to muffle things too much.

    [​IMG]

    Notice the effect vs shower mat alone on the 16 k spike. I know I can’t hear that high, but it rings like hell and maybe it was reinforcing a peak/ringing around 8 k (which I think is underrepresented in my measurements)...?

    [​IMG]

    [​IMG]

    Anyway, now I’m very happy with the sound. The combination of the shower mat’s downward curl of the upper midrange, the reduction in the mid-treble from the mat + tissue, and the tissue’s reduction of the upper treble peak seems to work really nicely with these phones.

    Now will get away from REW and back to listening. Thanks to everyone for this thread.
     
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  15. spoony

    spoony Friend

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    Good job! I found the mat helped the most with imaging, and the paper / felts with brightness. I listened to pairs with and without the shower mat and there was a discernible difference in precision.
     
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  16. naughtilus

    naughtilus Rando

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    Examining the Yamaha NS-10M “Tissue Paper Phenomenon”
    An Analysis of the Industry-Wide Practice of Using a
    Tissue-Paper Layer to Reduce High-Frequency Output

    Recording Engineer/Producer Magazine, February 1986 – by Bob Hodas

    I thought you guys might find interesting the conclusion in this article.
     
  17. naughtilus

    naughtilus Rando

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    Considering the effect from the tissue paper is comb filtering, that may explain why the checkered shower mat has such good results in measurements. I think trying out grids and rings, don't have to be necessarily foam, would bring more interesting results.

    IME with my K702s, everytime I solve the presence region nasties, something is wrong with the LF or the HF, or just the imaging and finer details get lost. So far I still haven't beaten the simple tissue paper behind stock foam ring mod by Purrin. After reading the article by Bob Hodas I tried different type of paper, napkins, toilet paper, regular kleenex stuff etc. I'll buy some wet wipes next, since they have different, more fibrous structure.
     
  18. Biodegraded

    Biodegraded Acquaintance

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    There seems to be more going on with the shower mat than is revealed in the measurements. @spoony detected improved imaging - not sure I noticed that myself but it certainly didn't get any worse - and it actually boosts the midrange slightly relative to the treble; I had to turn the volume down a bit to get 1 kHz back to 90 dB. If you can find something similar locally, combining it with tissue might give you a pleasing result.

    I like your hat.
     
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  19. ipm

    ipm Rando

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    Try a music store that sells microphones, amps, and similar gear. Such stores often carry AKG and other brands that people talk about on this site and they do provide parts and act a getaway for service if needed. I got genuine AKG pads for my K712 at a place in Toronto with no real hassles at all. They did all the hunting down of part numbers, found a source, and brought them in. It took about a three days to obtain them. I got HD650 pads at a music store in Burlington, Ontario in a similar way. My experience is that music stores often offer a better price than audiophile stores do.
     
    Last edited: Aug 20, 2017 at 12:02 PM
  20. spoony

    spoony Friend

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    I no longer own a K700 variant but thanks for the tip!
     

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