Custom Cans HD600/HD650 mod: measurements and impressions

Discussion in 'Modifications and Tweaks' started by Biodegraded, Dec 26, 2021.

  1. Biodegraded

    Biodegraded Friend

    Friend
    Joined:
    May 28, 2017
    Likes Received:
    5,324
    Trophy Points:
    113
    Location:
    Vancouver BC
    Custom Cans HD600/650/6XX mod: measurements and impressions

    Edit: This post started out in the Sennheiser HD650 Love (Appreciation Thread), which explains some of the references below. Thanks to @Tekker , @Baten and others there for the good reports that encouraged me to try this kit.

    -----------------

    Maybe this is more appropriate for a mods thread - but there have been a few mentions of it in this one, so here it is. If staff want to move it, fine by me.

    Intrigued by positive mentions here and elsewhere, I ordered this kit direct from Custom Cans. Excluding VAT it was GDP 29.17 + GBP 9.60 postage to Canada. Sure, I could have just done the KISS mod, but I would have had to buy Dynamat and I didn't want to kill any spiders, so I thought I'd give this a try.

    The kit consists of a pair milled copper rings that fit over the spider, 4 different pairs of foam inserts to go in the magnet hole (the existing foam disc(s) under the outer spider should be removed), and 3 stick-on gaskets (a pair and a spare) that look like sections through a coronavirus to stick over spiders with legs that are too skinny to hold the rings on their own (varies between models or generations):

    [​IMG]

    Besides adding mass the weight is purported to smooth the airflow, the combination resulting in "more detailed bass and a little more sub-bass", which can then be tuned to taste with the different foam plugs. The foams on the left are drilled through with tapered bores; they're placed opposite ways up for the photo. The ones on the right are the least dense material and have the number 3 stamped out through them. Of the remaining pairs, the blue (3rd from left) are more dense and slightly longer than the yellow (2nd from left).

    Applying the mod to my 2017 (Ireland) HD6XX, TLDR is that I mostly concur with @Tekker 's description a page back in this thread:
    But I'm not sure about the decrease in upper bass - seemed to me to be more a change in emphasis.

    Measurements were made on a flat-plate coupler which unfortunately rolls off in the lower bass so doesn't show relative differences there very well. FR (no compensation) shows the tonality differences of the ring & various foams. Yellow is stock, purple (topmost) is with no foam, blue is the bored foam, green the no. 3 foam, orange the yellow foam and red (lowermost) the blue foam.

    [​IMG]

    SPL of the input signal was set at 90 dB @ 1 kHz for the stock configuration and was not changed for any of the others. You can see big differences in the bass, about 7 dB between no foam and blue (densest) foam around 100 Hz, and small differences in the opposite sense from 1.5 kHz ~ 4.5 kHz.

    Wondering what could explain the differences in bass & upper-mid/treble quality, I had a look at distortion measurements & CSDs. I didn't see anything obvious in the latter, but I'll put a subset here in case more experienced eyes than mine spot something. Stock, no foam, drilled foam, densest foam:

    Senn HD6XX L CSD stock.jpg Senn HD6XX L CSD Cu.jpg Senn HD6XX L CSD Cu 5.jpg Senn HD6XX L CSD Cu 1.jpg

    Distortion seemed more interesting. Care is needed in the interpretation because of the different SPLs in the bass, but comparing measurements it's possible to see changes particularly in how the 3rd harmonic behaves. Ignore the big spikes in the bass, they're because of electrical noise nearby in my building. Let your eye follow the baselines and note how with more foam H3 is higher in the bass & lower mids compared to the other harmonics:

    [​IMG]

    [​IMG]

    [​IMG]

    Now just comparing the 3rd harmonics of all measurements - same colour scheme as the FR graph:

    [​IMG]

    Notice between about 40 & 200 Hz how the tan, green and orange curves (stock, '3' foam, yellow foam, respectively) are about the same but purple and blue (no foam, bored foam) are lower; and how the red curve (blue, densest foam) is higher from the bass up to about 400 Hz despite being lowest in level through there on the sine sweep (FR graph). Notice also the higher and increasing level of the stock (tan) curve above ~500 Hz.

    These curves represent the levels of the 3rd harmonic at the excitation frequency, so would manifest at ~120~600 and >~1500 Hz, respectively. However, they're all below -50 dB down from the fundamental level, so it's hard to argue that a few dB of difference down there would be audible. But maybe they cause or correlate with some other effect to generate the perception of more textured, better quality bass (don't know about the blue foam - as the FR shows bass is kind of absent with that one) and smoother upper mids & treble.

    My favourite configuration: I go between the bored foam and the '3' foam; '3' seems tonally the most balanced but bored seems timbrally the most correct across the range (and sometimes I don't mind a bit of extra bass).
     

    Attached Files:

    • Epic Epic x 13
    • Like / Agree Like / Agree x 9
    • List
    Last edited: Dec 27, 2021
  2. purr1n

    purr1n Super Friend

    Staff Member Friend BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    75,431
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    Oh my, what I have done!

    Anyway, I'm glad people are making solutions. This deserves it own thread.
     
    • Like / Agree Like / Agree x 4
    • List
  3. Drakkard

    Drakkard Facebook Friend

    Joined:
    Nov 24, 2015
    Likes Received:
    124
    Trophy Points:
    33
    Location:
    Saint-Petersburg
    Looks cool, but I assume applying dynamat (not blu-tack! it is worse) to the same place will provide the same or even better result. I really like applying dynamat to the driver housing all around. Recently tuned several AKG K1000 with it (also some other stuff but does not matter here) - effects are the same as described here, somewhat
    Looks not that pretty however
     
    • Like / Agree Like / Agree x 1
    • List
  4. Biodegraded

    Biodegraded Friend

    Friend
    Joined:
    May 28, 2017
    Likes Received:
    5,324
    Trophy Points:
    113
    Location:
    Vancouver BC
    The copper ring effectively lengthens the bass port, which might have its own effect.

    On that topic, I forgot to mention I tried the bored foams in both directions - first with the wider diameter to the inside, which produces a bore that's more or less similar in diameter or maybe slightly reverse-horny, and second with the wider diameter to the outside, which gives an obviously flared bore. Measurements didn't seem significantly different (wide-end-in are the ones shown above), but I thought there might have been a bit more sub-bass with the wide ends outward.

    Also: on my HD6XX pair there was only one foam disc on each side under the spider. Other generations or models have 2 or 3. Is it known how models with different numbers/thicknesses/compositions of discs measure or sound relative to each other? Wouldn't be surprised if that made as much or more difference as the various screens are supposed to...

    Edit: Nope, actually mine had 2 discs each side - they were just well stuck together.
     
    • Like / Agree Like / Agree x 2
    • List
    Last edited: Dec 27, 2021
  5. purr1n

    purr1n Super Friend

    Staff Member Friend BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    75,431
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    If we significantly lengthen the port, we'll get a peakage at 3.5-4kHz. At least this is what I remember from my experiments. Looks like there is a small effect from the lengthening of the "port" from the copper ring.
     
    • Like / Agree Like / Agree x 1
    • List
  6. Armaegis

    Armaegis Friend

    Friend BWC
    Joined:
    Sep 27, 2015
    Likes Received:
    5,162
    Trophy Points:
    113
    Location:
    Winnipeg
    Request to rename the thread title part from HD6-- to HD600/HD650. Reading it right now looks like it says HD6 which is a very different headphone in the Sennheiser lineup.
     
    • Like / Agree Like / Agree x 4
    • List
  7. Martigane

    Martigane Rando

    Joined:
    Mar 5, 2019
    Likes Received:
    74
    Trophy Points:
    13
    Location:
    Belgium
    Constricting the airflow on the back of the magnet had similar effects on THD when I did it on HD58X, but there, the foam improved CSD and frequency response:
    https://www.head-fi.org/threads/mas...ew-measurements.867972/page-284#post-15305131

    I also see that the foam from this kit is quite thick. You could probably still rip the benefit of back damping with thinner foam, all the while having less attenuation below 50Hz (and lower THD). Something to try maybe :)

    It's interesting that they chose copper. Looking at the slightly lower THD at high frequencies, I wonder if this ring acts as a magnetic demodulation ring, as they do on speakers (it is quite far from the coil, and on the wrong side, but who knows)
     
    • Like / Agree Like / Agree x 4
    • List
  8. Biodegraded

    Biodegraded Friend

    Friend
    Joined:
    May 28, 2017
    Likes Received:
    5,324
    Trophy Points:
    113
    Location:
    Vancouver BC
    Here are CSDs for stock and foam 3 with floors now ~50 dB down from the fundamental through the mids & lower treble, and as unsmoothed as I can get them (any tips on settings gratefully received, btw):

    [​IMG]

    [​IMG]

    The stock configuration does show a ~5k ridge similar to your stock 58X measurement, and maybe a bit more relief in the foothills in the 7-10k area. As you said, though, it's very deep.
    The sub-bass rolloff in my measurements is mostly my equipment, not reality. But yeah, there's plenty of scope for playing with different foam plug densities and thicknesses. Interesting thought about the copper - I imagine if that had've been the intent they would've been quick to say so, but comparing a ring of similar weight made from non-conductive material could be fun.
     
    • Like / Agree Like / Agree x 1
    • List
  9. purr1n

    purr1n Super Friend

    Staff Member Friend BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    75,431
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    done
     
    • Like / Agree Like / Agree x 2
    • List
  10. Tekker

    Tekker Acquaintance

    Joined:
    Aug 1, 2020
    Likes Received:
    57
    Trophy Points:
    28
    Location:
    Netherlands
    I forgot to say: I kept the stock foam on my HD650 when I inserted the copper ring, so I don’t know how they sound with the foam removed or the included white foams.
     
  11. econaut

    econaut Facebook Friend

    Contributor
    Joined:
    Feb 5, 2017
    Likes Received:
    213
    Trophy Points:
    43
    Location:
    EU
    LOL I just did this copper mod a moment ago with my 650s and wanted to check SBAF for the views on this mod that I had read here before ordering. And now this thread with the measurements. Great timing :)

    I took the stock foam out, because I had the feeling that the copper ring would not stay in place if I had left the foam there.

    I just quickly checked the Custom Cans foam inserts, but prefer the sound without any foam because it gives the most bass.

    In total I think there is some added clarity which makes them sound a little more forward. Initially I preferred the more laid back stock sound, but I am getting used to the new sound signature right now.
     

    Attached Files:

    • Like / Agree Like / Agree x 1
    • List
  12. Biodegraded

    Biodegraded Friend

    Friend
    Joined:
    May 28, 2017
    Likes Received:
    5,324
    Trophy Points:
    113
    Location:
    Vancouver BC
    Maybe that accounts for our different perceptions of the upper bass. If you want to try the full meal, the stock foam will come out in one piece if you start by pushing it in between the legs of the spider and then pulling it gently out through the centre hole (use tweezers). I think reversing the process would get it back in ok too, but I haven't tried that.
     
  13. wormcycle

    wormcycle Friend

    Friend
    Joined:
    Aug 13, 2016
    Likes Received:
    1,404
    Trophy Points:
    113
    Location:
    Toronto, ON, Canada
    I was just watching the Custom Cans video and about 1 min into it it is said that removing the foam behind the driver is "very difficult to reverse". Does it make sense to make the copper mode without removing the original foam?
     
  14. Biodegraded

    Biodegraded Friend

    Friend
    Joined:
    May 28, 2017
    Likes Received:
    5,324
    Trophy Points:
    113
    Location:
    Vancouver BC
    I saw that video only after ordering the kit, and it did give me pause because I was hoping for a fully reversible mod. However, I've just tried it on one side and with gentle persuasion with a toothpick it's possible to get the foams (plural - turns out mine did have two discs per side, but they were stuck together so well by their shared life that they came out as one) back in. You do have to work at it carefully under the legs of the spider until it stops looking like a cartoon sun or amputee octopus...

    You could put on the copper over the original foam, and @Tekker reported a good result by doing that, but because of the underlying discs the copper rings would stand a bit more proud of the magnets and you wouldn't be able to experiment with the different plugs, so all things considered I'd remove them.
     
    • Like / Agree Like / Agree x 3
    • List
  15. econaut

    econaut Facebook Friend

    Contributor
    Joined:
    Feb 5, 2017
    Likes Received:
    213
    Trophy Points:
    43
    Location:
    EU
    I guess the most important thing is to get out the stock foam(s) intact and not to rip it/them apart. Then the mod is reversible - in theory. Or even practically as @Biodegraded has shown in the above post.

    If one is careful, not ripping the foam apart is not too hard. I had to watch the video many times until I understood what he was doing there exactly.

    But actually the way shown in the video did not work for me. I was not able to push the foam at the spider legs as shown in the video. I had to push the foam between the spider legs. This way I managed to push it to the middle in order to pull it out afterwards.

    Soundwise it's not too important to have it easily reversible IMHO. After removing the stock foam you have five different tuning possibilities with the copper ring in place (4x foam plus 1x no foam) and will probably find a tuning to your liking.

    EDIT: In my case the copper ring would not hold on to the spider cage with the stock foam in place. That was the reason I pulled it out.
     
    • Like / Agree Like / Agree x 2
    • List
    Last edited: Dec 28, 2021
  16. Biodegraded

    Biodegraded Friend

    Friend
    Joined:
    May 28, 2017
    Likes Received:
    5,324
    Trophy Points:
    113
    Location:
    Vancouver BC
    More measurebation to better illustrate distortion differences in the bass...

    Here are frequency response curves for different configurations taken with SPL 96 dB @ 100 Hz. The colour scheme is the same as in the first post, tan = stock, purple = no foam, red = densest (blue) foam:
    [​IMG]

    Now dumping all distortion measurements for the same readings - first stock again, for reference:
    [​IMG]

    Copper ring only, no foam:
    [​IMG]

    Bored foam:
    [​IMG]

    '3' foam:
    [​IMG]

    Yellow foam:
    [​IMG]

    Blue foam:
    [​IMG]

    Overlaying all the third harmonics, you can see how they vary in the bass when SPL is similar there - lowest with the least foam (purple, blue), foam 3 (green) pretty similar to stock, higher with denser foam (orange, red):
    [​IMG]

    In combination with the overlay in the first post: if these measurements reflect reality (have to admit they're pretty noisy), they indicate that adding the copper ring slightly reduces 3rd harmonic distortion in the upper mids & treble and that more/denser foam plugs markedly increase it in the bass.
     
    • Like / Agree Like / Agree x 6
    • List
  17. jfunk

    jfunk Rando

    Joined:
    May 28, 2020
    Likes Received:
    22
    Trophy Points:
    3
    Location:
    cheltenmham
    Howdy... I originally designed this kit so thought I would give a little background.
    Originally we were modding HD600s by adding lead weights behind the driver but we were individually shaping the weights and it was not something we could sell as a DIY kit which is why I started developing this one with the aim of it being easy for anyone to fit.
    Copper was chosen for a few reasons, it is quite dense, CNC machinable and it looks quite nice ;) It does also have diamagnetic properties but that is not something we tested properly.
    We started off by trying lots of different profiles and heights by 3D printing them and weighting the 3Dprints with lead. Once we found a good balance we got the 1st batch CNC machined.
    Unfortunately our 3Dprints had a bit more flex than the copper one and when they arrived they did not fit and we had to widen all the grooves in them by hand which sucked a lot.... But we learnt a lot and on the second batch the grooves had a slight draught angle so they would fit tightly but would also be removable.
    We did a little more testing and some people did not like the extra bass levels which is when we came up with the idea of the foam inserts. Again we tried loads of different densities and thicknesses to see how they affected the sound. Originally there were two that looked the same so I decided to engrave a 3 on one to make it easier to tell them apart but we had the laser power set too high and it cut a 3 all the way through.... turned out that made it sound just right so we kept doing that for the final Kit.
    So... I would like to say that I scienced the sh*t out of it but it was mostly a bit of intuition and a lot of trial and error.
    We have just about sold enough of these to break even now and may be doing a version painted black for a stealthier look soon
     
    • Like / Agree Like / Agree x 19
    • Epic Epic x 1
    • List
    Last edited: Dec 30, 2021
  18. Biodegraded

    Biodegraded Friend

    Friend
    Joined:
    May 28, 2017
    Likes Received:
    5,324
    Trophy Points:
    113
    Location:
    Vancouver BC
    Thanks for the history! Personally I like the look of the copper so would go for that even if black was available - but if you can provide a choice, great.

    Edit: @jfunk good to have you here and if you're planning on being around regularly, you might want to ask the mods for a 'MOT - Custom Cans' or similar tag.
     
    • Like / Agree Like / Agree x 4
    • List
    Last edited: Dec 30, 2021
  19. Baten

    Baten Friend

    Friend
    Joined:
    Mar 18, 2018
    Likes Received:
    950
    Trophy Points:
    93
    Location:
    EU
    Short note. Compared HD600 custom cans copper ring mod vs HD650 kiss mod. Oh wow, after so long of using the first; the modded 600, it just sounds simply more extended in both ends... the 650 sounds dark and veiled(sorry) in comparison, but the bass is also noticeably better defined on the copper modded HD600.

    I'm enlarging the differences to be clear, it's still obviously the same headphone family. But I don't think I can get into the 650 anymore unless for some extreme laid-back sessions, having both on hand :)
     
    • Like / Agree Like / Agree x 3
    • List
    Last edited: Jan 9, 2022
  20. neogeosnk

    neogeosnk Friend

    Friend
    Joined:
    Sep 28, 2015
    Likes Received:
    1,620
    Trophy Points:
    93
    Location:
    Los Angeles, CA
    Can this be used on already Kiss modded headphone? Meaning since some of the spider cage was cut will the copper ring stay in place?
     

Share This Page