|
Post by ihack13 on Dec 15, 2018 13:58:54 GMT
About modding the HD688. Cant I just make an external circuit?
I have female and male audio jack connectors and the electrical components for the HD 681 circuit. But they seem to deviate as it seems. the inductor is 0.47mH and the capactiors are 47uF
edit: ok nvm
"The filter modification below only replaces the single toilet-paper ply shown above. It is not an additional modification. All the other mods described on the previous and following pages still need to be done."
|
|
|
Post by miiksu on Dec 15, 2018 19:46:17 GMT
I still can't get off the annoying dips around 2650 Hz and 4500 Hz. Real leather measures nicely up to 2 kHz and after that it got that big 16 dB dip. Velours it have only 6 dB dip. That kinesio tape helped slightly on the upper frequencies and some cotton added to edges but I the dip got worse.
|
|
solderdude
Administrator
measureutternutter
Posts: 4,881
|
Post by solderdude on Dec 15, 2018 23:11:18 GMT
Pad swapping has a tendency to change one aspect positively and others negatively. The driver output of the HD688 is recessed but can be lifted a few dB with EQ without too much negative effects.
|
|
|
Post by miiksu on Dec 16, 2018 11:49:02 GMT
Pad swapping has a tendency to change one aspect positively and others negatively. The driver output of the HD688 is recessed but can be lifted a few dB with EQ without too much negative effects. Interesting. I got it now better with ur advice. It's only now +6 and -12 dB. Let see if I can make it more smoother. Upper frequencies are now almot smooth but elevated. Very easy to lower and fix. But the dip need to be lower. I love the sheep skin pads. They don't make my ears hot and better attenuation for output noise. Edit. I'm getting closer. +6, -9 dB. Used three layers of felt sheets. Thickness approx 2 mm. Cutted to 100mm circles.
|
|
|
Post by miiksu on Jan 13, 2019 15:49:39 GMT
New pads and new mods. I got it to approx +6 / -6 dB. I need to test more but it's quite OK atm. From 4 kHz to 10 kHz could be lower otherwise quite nice. Of course after EQ it's much more pleasant and very flat. No felt is used with this modification wink My materials; a soft clay, a toilet paper, a cotton pad, a kinesio tape, a adhesive foam sheet. Cheap materials that can be finded everywhere. No irreversible modifications.
Cumulative spectrum delays as well. Got it quite clean. The driver behaves different after EQ. 2-8 kHz cleaner but then very small delays happening 9 kHz and around 18 kHz. May me possible to remove those but not sure if it's worth the time. This does not tell the impact on sound but it has damn good bass, clean middle to upper frequencies. And my mods. I filled the cups with 50 grams of soft clay and covered the rest with cotton that is splitted to half and trimmed to size in the photo. Both sides are covered with cotton. The size is not too crucial on the back side just try to mimick best as you can. If you look more closely. Also some kinesio tape or pharmacy fabric tape to the middle. It's black on my pictures. 3mm adhesive foam ring is covering the driver outlet hole, just for the edges. It slighly helped to get better bass response. So I keeped it. The toilet paper is 3-layer with three invidual layers. Thee circles 74 mm, two of them has 30 mm holes and one has 8 mm a hole. Also a cotton pad splitted to half and the hole need to be 8 mm as well but in my picture it's something like 9-10mm. A bit of error Also 3x3mm adhesive foam to cover the grill on the front, foam wall added to make more space and kinesio tape to block the hole on the front. I bought from this seller these quality pads: www.ebay.com/itm/For-AKG-K240-S-K241-K242-K270-K-Series-Headphones-Ear-Pads-Seals-Velour-thicker/122893437911?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649I recommend these new 110mm velour pads: www.ebay.com/itm/Velour-ear-pads-seals-pillow-foam-cover-Cushion-for-headphones-Full-size-for-all/323353580025?ssPageName=STRK%3AMEBIDX%3AIT&var=512414971937&_trksid=p2057872.m2749.l2649Measures slightly better and gives more volume and impact. Also better comfort because it's bigger also.
|
|
|
Post by miiksu on Jan 31, 2019 19:53:36 GMT
Sorry again I'm only one here but here is my latest modification. My intentions was to make pads more deeper then again somehow I got 2.5 kHz area better. I'm just lucky with HD688. It did not work with the HD687. I lost few desibels with the HD687 and did not measure any better or even slightly worse and did not sound any better. I noticed that new mod with HD688 sound was more dynamic. The bass was same, maybe because upper middle was more there and treble a bit softer. I did not do anything super analytical. Added second foam wall to the front and coated shiny plastic area with kinesio tape. See the picture. My measurements. 30Hz - 3.5kHz +-3.5 dB. Still hot treble but slightly more listenable on some hot treble songs. Edit. Then again you can add small amout cotton to the middle between foam pads and the grill on the front and get rid of the hot treble but then again you get very deep dip around 3900 Hz. If you don't planning EQ and using only phone then this may be the best choice for you.
Edit. Pictures how much the cotton and where to apply. I must say I enjoyed it a lot. The sound was very balanced and good sounding. Maybe a bit thinner to compared without the cotton at middle and after EQ it's just flat as possible. I prefer EQ but if u don't wanna do it, then do something else I need to try Frans filter circuit mod when I get the parts. It may make it even better without using EQ or the cotton at middle.
|
|