Sennheiser HD650/M Compendium

Discussion in 'Headphones' started by zonto, Nov 9, 2016.

  1. zonto

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    SENNHEISER HD650/M COMPENDIUM

    Given the recent influx of new members, we began to see a number of questions resurfacing that were previously covered in various threads. As such, the community has compiled information and resources about the Sennheiser HD650 (both stock, "HD650," and modded, colloquially referred to as "HD650M" for the traditional SBAF mods (much to @JoshMorr's chagrin) and "HD650K" for the newer KISS mods), to be supplemented as the community knowledge-base grows. Though the focus of this resource is on the HD650, due to many similarities within the HD6x0 family this should also be a helpful resource for Sennheiser HD600 ("HD600") owners.

    In November 2016, Massdrop released a customized version of the HD650 called the HD6XX. Other than a different paint job and a shorter cable the HD6XX appears to be identical to the HD650.

    To keep the S/N ratio high in this thread, please do not post here. Instead, please PM me if you have suggested revisions or are aware of other helpful resources.

    Note that though this Compendium is rather comprehensive, it is not totally so. If you cannot find an answer to a question here, please search the forum and/or the main HD650 threads linked to below before posting in the threads. Our discussions have been nuanced, but not exhaustive.

    Thanks to @Dino for his extensive usability testing.

    • 06/27/2017: Added link to HD580 thread.
    • 01/09/2017: Impulse/burst measurement thread and 10kHz and 100Hz measurements added.
    • 02/20/2017: Added link to @Rthomas' "expensive cables" thread discussing use of Cardas upgrade cables with HD650/HD600. See "FAQ–Cables–Third-party cable options" below.

    TABLE OF CONTENTS
    1. Quick References (this post)
    2. Measurements (this post)

    QUICK REFERENCES
    General

    • HD650 product page
    • HD650 Instruction Manual (revised November 2016)
        • Frequency response: 10–41,000 Hz
          • Nov. 2014 manual: 16–30,000 Hz (-3 dB); 10–39,500 Hz (-10 dB)
        • Transducer principle: dynamic, open
        • Frequency characteristic: diffuse field equalized
        • Nominal impedance: 300 ohms
        • Sound pressure level at 1 kHz: 103 dB (1 Vrms)
        • Long-term input power: max. 500 mW as per EN 60-268-7
        • THD: ≤ 0.05% (1 Khz, 100 dB)
        • Contact pressure: approx. 2.5 N
        • Ear coupling: circum-aural
        • Weight: approx. 260 g (without cable)
        • Connector: 1/4" (6.3 mm) stereo jack plug
        • Adapter: 1/4" (6.3 mm) stereo jack plug to 3.5 mm stereo jack plug
        • Connection cable: oxygen-free copper cable (OFC), 3 m
        • "With the HD 650, Sennheiser has followed the changes in listening habits of music lovers and the way in which they experience sound. In spite of all purism and the highest demands on precise sound reproduction, a slight change in listener behavior is detectable. Today many music lovers want to feel the sound more instead of plainly analyzing it. The HD 650 now captivates your senses where you used to be a mere observer. It allows total submersion into an ocean of music and lets you completely forget your surroundings." (HD650 Instruction Manual at 2)
        • "In their quest to develop even better dynamic headphones, Sennheiser consulted high-end specialists, sound engineers and trade journalists. They even consulted internet forums to complete the picture. This intensive research revealed an interesting fact: that listening habits have changed. Today, people prefer to 'feel' the music rather than to analyze it. The result was the HD 650 – headphones that captivate the listener with the ultimate in lifelike reproduction, while still maintaining absolute precision." (source)

          Note:
          We cannot locate the original HD 650 press release from which the above quote originates.
    • Solderdude's Sennheiser HD650 treatise ("Solderdude")
      • Note: Please download/retain a copy of this document. We reference it frequently below, always with the relevant page numbers (e.g., "Solderdude, X"), but the PDF is too large to upload as an attachment to this post.
    SBAF
    Inner|Fidelity
    Headfonia

    MEASUREMENTS
    SBAF

    @Marvey's HD650 measurements (source)
    [​IMG]


    @Marvey's HD650 measurements (source)
    [​IMG]
    [​IMG]


    @Marvey's Massdrop HD6XX measurements (source)
    [​IMG]


    @Marvey's HD650 (orange) vs. Massdrop HD6XX (yellow) (source)
    [​IMG]
    sonarworks' measurements of HD650 vs. HD600, shared by @Psalmanazar (source)
    [​IMG]


    @Bill-P's HD580 vs. HD600 vs. HD650 measurement (source)
    [​IMG]


    Old HeadRoom HD600 vs. HD650 vs. HD800 (vs. Denon AH-D2000... build-a-graph is down)
    [​IMG]


    @Marvey's HD650 (w/ Dynamat) (magenta) vs. HD600 (cyan), each in HD600 cup/screen (source)
    [​IMG]


    @Marvey's HD650 (w/ Dynamat) in HD600 cup/screen (magenta) vs. HD650 cup/screen (w/ coin mod and rear foam removal) (source)
    [​IMG]

    Note: "[ S ]ennheiser knew what they were doing and that the HD650 driver is best in an HD650 cup, and likewise HD600 driver is best in an HD600 cup." (source)

    @JK47's measurements of HD650M (coin mod and rear foam/spider removal, no damper) vs. HD600 (source)
    [​IMG]


    @Marvey's HD650 KISS vs. old HD600 measurements ("Take with grain of salt . . . .") (source)
    [​IMG]
    Note: See "Modifications" below for measurements of the effects of individual mods.

    @Marvey's HD650 vs. HD650M (community mods: coin mod, rear foam / spider removal, damper) vs. HD650 KISS (source); see also @Yeskey's HD650 KISS vs. HD650M measurements
    [​IMG]


    @ultrabike's HD650 vs. @Ryu's HD650M (source) Note: different coupling.
    [​IMG]


    @Marvey's HD650M (blue) vs. Focal Elear (yellow) vs. Ether Open (purple) (source)
    [​IMG]


    @Marvey's HD650M (yellow) vs. Focal Utopia (purple) (source)
    [​IMG]

    See
    burst/impulse measurements of HD650K: 10kHz, 100Hz.

    Inner|Fidelity

    Solderdude
    • HD650 (Solderdude, 3)
    • HD600 silver screen vs. HD650 black screen (Ibid., 6)
    • Distortion (Ibid., 7)
    • Square-wave and needle pulse response (Ibid., 8–11)
     
    Last edited: Sep 5, 2017
  2. zonto

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    FREQUENTLY ASKED QUESTIONS

    General
    Pros
    • Extremely resolving
    • Scales well with better electronics
    • Balanced frequency response (see "Measurements" above)
    • Modular construction: all parts user-replaceable
    • Smooth treble
    • Liquid, cohesive midrange. Great vocals.
    • All of the above for a low price = great value
    Cons
    • Lack of clarity and transient response compared with some headphones
    • Sennheiser "veil" (see "Has the HD650 changed over time? Black vs. silver screens" below)
    • Lack of subbass (see "Measurements" above)
    • Some find clamping force uncomfortable (see "Headband / Clamping Force" below)
    • Cheap finish (in some ways) (source)
    • Slight ~5kHz glare/ringing. See (source); (source); (source); (source). Mods and proper amplification likely alleviate this. (source)
    Weighing all of these factors, the HD6x0 was awarded a 2015 Golden Schlong Award (NSFW)

    • HD600 product page
    • HD600 Instruction Manual (revised November 2016)
        • Frequency response: 12–40,500 Hz
          • Nov. 2014 manual: 16–30,000 Hz (-3 dB); 12–38,000 Hz (-10 dB)
        • Transducer principle: dynamic, open
        • Frequency characteristic: diffuse field equalized
        • Nominal impedance: 300 ohms
        • Sound pressure level at 1 kHz: 97 dB (1 Vrms)
        • Long-term input power: 0.2 W as per DIN 45580
        • THD: ≤ 0.1 % as per DIN 45500
        • Contact pressure: approx. 2.5 N
        • Ear coupling: circum-aural
        • Weight: approx. 260 g (without cable)
        • Connector: 1/4" (6.3 mm) stereo jack plug
        • Adapter: 1/4" (6.3 mm) stereo jack plug to 3.5 mm stereo jack plug
        • Connection cable: oxygen-free copper cable (OFC), 3 m
          • Note: After the Nov. 2016 HD600 manual revision, the "Connector," "Adapter," and "Connection cable" entries in this table are now identical to the corresponding entries in the HD650 manual. Thus, it is unclear whether this means new-production HD600s are now shipping with the HD650 cable or whether they will continue to use the old HD600 cable.
    • See "Measurements" above.
    "Sennheiser has actually used a tougher metal mesh for the earcups that shouldn’t dent as easily as the old stuff. (I welcomed this news — my 600s, which have traveled to many a recording session, are quite banged up.) The whole structure of the HD 650 seems far more solid and less resonant than that of its predecessors, possibly as a result of a stronger spring in the headband. Sennheiser states that it has beefed up the 650’s 'baffling damper' — a membrane that controls the chamber resonances of and within the earcups themselves — for 'tighter acoustic control.' If that means the headphones feel dead-quiet and free from any structural vibration, then: mission accomplished.

    "But the biggest changes in the HD 650 are the aluminum voice-coils, the new diaphragm material, and a Kevlar-shielded OFC cable that sports a dedicated 1/4″ phono plug (a phono-to-miniplug 'cable reducer' is also provided). In addition to being made of a different material, the 650’s diaphragms are constructed differently — it’s a membrane of variable thickness that has been tuned by ear. Not only by ear — Sennheiser has comprehensive test and measurement facilities — but engineer Axel Grell found that when the ‘phones measured flat, they sounded harsh. So he very carefully tuned the response to have notches at 5kHz and 16kHz. These notches, speculates headphone maker-designer [ @Tyll Hertsens ], of HeadRoom, mimic the ridge notches of the concha — the largest and deepest concavity of the external ear, or pinna — which help you determine the azimuth and elevation of sounds." (source)
    • The HD600 is more neutral, the HD650 more colored.
    • The HD600 is more forward, the HD650 is more laid back.
    • The HD650 is darker, while the HD600 has more lower treble and upper midrange presence.
    • The HD600 has a more balanced frequency response (one of the best, in fact), the HD650 is more low-end heavy.
    • The HD600 can maintain a faster pace, the HD650 is generally slower.
    (source)
    Additional @Psalmanazar impressions

    Additional @Hands HD600 impressions


    Other Impressions
    Upon its release in 2003, Sennheiser utilized black silk acoustic screens around the HD650 driver. At some point, Sennheiser swapped this black silk to a silver metal mesh, per the below:

    [​IMG]

    Some argue that it was the black acoustic silk that led early HD650 listeners to coin the infamous term: "Sennheiser veil." See (source) ("There is some anecdotal evidence that the latest HD650 that come with the silver screens aren't as veiled as the old ones with the black screens."); (source) ("The silver screen material is more rigid, which leads me to believe that it isn't too resonant at lower frequencies, and that may be why the HD650 is less veiled."); (source).

    "Apparently sometime ago Sennheiser quietly changed the drivers on the HD650, HD600, and HD580 models. While the old ones have black screen, the new ones are white. The material of these screens were changed as well. They may have changed other things inside the drivers as well, but we can’t tell for sure.

    "What we do know, is that now these new Sennheisers have lost their dark and veiled sound. Instead, they are sounding very neutral, nice and detailed, while still retaining their laid-back presentation. No more muddyness, no more veil. It’s interesting because this driver change may have happened as early as 2007 . . . ."

    (source; see also user comments)

    @stratocaster's measurement of HD650 behind both the black and silver screen (source)
    [​IMG]

    But see @stratocaster's measurement of an HD600 in its silver screen capsule and an older HD580 capsule (source)
    [​IMG]

    Thus, some ambiguity remains. Either way, Sennheiser probably changed from silk to metal mesh for long-term durability so the latter is worth it just for that. Purchasers have received the "silver screen" version in both the older, silver packaging and the newer, black packaging. (source)

    Occasionally, we are asked about a "white screen" HD650. This is misinformation and should be disregarded. See (source); (source); (source).
    Note: Prices below are in U.S. dollars.

    The MSRP for the HD650 is the same it's always been at $499.95. Street prices are lower of course.

    HD6XX
    The market changed in November 2016 with Massdrop's release of the HD6XX at $200. Demand was so high for the initial drop of 5,000 units that Massdrop sold out in about an hour, servers crashed, orders couldn't be completed, and blood ran through the streets (source). We're optimistic there will be future drops.
    • Note: The HD6XX stock cable is 6ft long. The HD650 stock cable is 3m (~10ft) long. Need for a longer cable undercuts the value proposition of the HD6XX. See "Cables" below.
    Back in the real world:

    New
    • $300 shipped is a reasonable target price for a new pair of HD650 in the United States.
    • Prices on Amazon.com have dropped as low as $287 (source); (source).
    • @zonto has purchased two pairs from Sonic Electronix (authorized retailer) for $300 and $295 shipped. (source)
    • Try Amazon.co.uk too. During summer/fall 2016, the price, converted to U.S. dollars, for the HD650 shipped to the United States hovered around $290. (source; see also posts that follow)
    • Monitor The Deals Thread for deals and set up a SlickDeals Deal Alert for "Sennheiser."
    Used
    • Monitor the Used Deals Thread and the For Sale forum for deals.
    • Check hifishark.com to ensure the price is reasonable ("hd650" search).
    • Sennheiser headphones hold their value, so don't expect firesale prices on used pairs.
    • Remember that a used pair may have a stretched metal headband and will probably require new pads. See "Pads" below. The latter point drastically undercuts the value proposition on used pairs, so tread carefully.
    See this post and the responses that follow. Potential candidates include HD650 with wood cups, JVC DX1000, Enigmatic Audio (LFF) Slant, Fostex T50RP, and ZMF headphones (see ZMF EIKON & ZMF ATTICUS thread).

    Pads
    Solderdude
    • As the pads become older/softer, because "the softer pads move the driver closer to the ear the bass portion is relatively louder." (Solderdude, 4 (showing measurements of new vs. old pads)). Thus the sound with old pads is "warmer." (Ibid. ("When the pads become softer /more compressible over time, the bass increases relatively and the headphone becomes more 'mellow' and less 'trebly'."))
    • "[T]he treble part with new pads is relatively higher and thus sounds slightly 'clearer' than when using the old pads." (Ibid., 5–6 (displaying more pad measurements and discussing sound quality differences/preferences)).
    • "Both the frequency response, distortion plots and above all square-wave and impulse response plots show how 'warm', bassy and 'slow' the HD650 with older pads is." (Ibid., 13–14 (displaying aforementioned plots)).
    SBAF
    • @sorrodje: "With new pads, the HD650 is definitely another beast. much more open & precise , less mushy and more balanced." (source)
    • @Psalmanazar: "[The new, stiffer pads] reduce the mid-bass and lower-midrange hump of every can in the line." (source)
    • @Hands: "Worn out pads are usually bassier and more rolled up top, though on occasion and depending on various factors can cause some spots in the treble to sound a bit more strained or grainy. Stage is usually smaller too." (source)
    "The original Sennheiser pads appear to be the best choice. I haven't measured cheap (often Chinese) nonoriginal 'replacement' pads but my guess is that original pads are the ONLY recommended ones." (Solderdude, 15) After measuring stock pads, Brainwavz HM5 pleather and HM5 velour, and Shure SRH940 third-party pads, Solderdude concluded the "plots show the superiority of the original pads." (Ibid., 15–18 ("My advise [sic] .... stick to the original pads if you want the most realistic/neutral sound.")).


    Additional Resources

    HM5 Pads
    Brainwavz Pads
     
    Last edited: Dec 13, 2016
  3. zonto

    zonto Friend

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    FREQUENTLY ASKED QUESTIONS, cont.

    Headband / Clamping Force
    • @thegunner100 "For those looking to reduce the clamp on their senns, extend the cups all the way down and bend ONLY the metal part with equal force on both sides. Do not bend the plastic headband." (source)
    • @Dino's helpful post on removing the metal ear cup to aid in metal headband stretching
    Never fear if you were overzealous and did something like this:
    [​IMG]

    @TRex's profile post re: snapping the headband. Helpful options discussed include:

    Cables
    As discussed above, the stock HD650 cable is a "Kevlar-shielded OFC cable that sports a dedicated 1/4″ phono plug." It is thicker gauge and more robust than the HD600 cable, in addition to making a better connection to the headphones. (source)
    Note: Unlike the HD650 cable, the HD600 cable comes terminated with a 3.5mm plug and is converted to 1/4" with a plug/sheath.
    The general consensus is that your money is better spent elsewhere if you're looking for sound quality differences.
    • Over time, we have seen recommendations of silver cable upgrades to attempt to cut through the "Sennheiser veil." There does not appear to be an objective basis to do so. (Solderdude, 14 (displaying copper vs. silver cable measurement plots from 10Hz to 30kHz)). "Feel free to draw your own conclusions whether or not the HD650 became brighter or more detailed, tightened the bass and improved the sound-stage, air etc. Other measurements all showed NO differences." (Ibid.)
    • "Personally I would only change the cables for either aesthetic reasons (colour or looks), when it is broken or the wire has an inconvenient length." (Ibid.); see "What if I need a balanced (XLR) cable connection?" below.
    • SBAF thread: Expensive Headphone Cables - A personal investigation (discussing upgrade from stock HD650 cable to Cardas Cross). See also "Third-party cable options" below.
    If you need a balanced cable, the general consensus is that the best value is to re-terminate the stock HD650 cable with XLR connectors.

    Re: the above quote:

    SBAF DIY Resources
    See "Third-party cable options" below if you prefer to purchase a pre-terminated XLR cable.
    If you do not wish to re-terminate the stock cable to XLR or simply wish to upgrade your stock cable, below are recommendations/resources to look into. Plenty of us believe in subjective differences between cables, but there has not been much discussion on SBAF with respect to sound quality of HD650 upgrade cables.

    SBAF Recommendations
    Other Resources
    Cardas Audio
    The classic Sennheiser HD6x0 upgrade cable is the Cardas Audio Cross.
    Cardas has since developed the Clear Light and Clear lines. Some New England meet impressions of HD650 Cardas cables are available on HF starting here (ViperGeek and skullguise posts, continuing to page 2 of the thread).

    Miscellaneous
     
    Last edited: Jun 13, 2017
  4. zonto

    zonto Friend

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    FREQUENTLY ASKED QUESTIONS, cont.

    Amplification

    Yes. Setting aside the fact that you need an amplifier to listen to any headphone, the HD6x0 deserve proper amplification due to their electrical characteristics and supreme scalability. A few considerations:


    Note:
    The above discussion does not revolve around getting enough volume out of the HD650. As Solderdude states:
    "To drive the HD650 to comfortably loud levels you only need around 1.7VRMS = 10mW into 300 [ohms] though." (Ibid., 55) "The HD 650 has a high impedance (300 ohms) and needs more voltage than most portable devices and PC headphone outputs can provide. Generally you need about 2 volts RMS (5.7 volts peak-to-peak) for wide dynamic range music at realistic levels." (source)

    Proper amplification, however, involves more than obtaining enough volume. See (source, and posts that follow).
    Output Impedance
    "The sonic signature of the HD650 is also dependent of the output resistance of the used amplifier." (Solderdude, 13 (displaying HD650 frequency response measurements with both 10-ohm and 120-ohm output resistance) and (concluding that "[if] you want slightly (about 1dB) more bass/warmth in the HD650 use it from a high output R amplifier")). The higher the output impedance, the larger the bump in bass response.

    Voltage Output vs. Current Output Amplifiers
    Solderdude discusses the differences between voltage output amplifiers and current output amplifiers. (Solderdude, 52) In the HD650's case, he concludes that a current output amplifier "would be great for increasing the speed of the driver, but the substantial rise in the impedance in the 100Hz area will also be 'lifted' in amplitude. (Ibid., (displaying HD650 impedance plot)); see "Measurements—Inner|Fidelity" above. "The impedance rises about 60% so the bass will be lifted about 4dB. The impedance rise above 7kHz is caused by the voice-coil inductance. At 20kHz the impedance is just 12% higher so just +1dB." (Solderdude, 52 (concluding that "[a] current drive amplifier thus is not well suited for the HD650 unless you want the headphone to become much more bassy")); see ibid., 12–13 (discussing current source amplification)).

    "The reality is you just need enough VOLTAGE when you want to drive the HD650 loud and nice." Id. at 16.

    Apogee Groove
    On April 5, 2016, Sennheiser announced its "perfect partnership" with Apogee and the release of a new bundle of the HD650 with the Apogee Groove USB DAC/amp which uses Contant Current Drive™ technology (press release). I have posted about my skepticism of this "perfect" pairing on Head-Fi. It is a decent option for a dongle, but the headphones deserve better.

    Inner|Fidelity
    SBAF
    • Anyone heard the Apogee Groove? and Suggestions thread
    • Apogee Groove with Apple Iphone 6+ working well. thread
    • @Psalmanazar quoting a HF review ("OVER THE TOP!")
    SBAF typically recommends a good tube amp for everything the HD650/M.
    More from @Hands: one / two


    Tube Amplifiers for HD650
    A good place to start your research is the SuperBAF Cheap Tube Amp Guide ~$1200 or less thread. It compares the following tube amps:

    The Glenn Studio OTL was omitted from the <$1200 list in the aforementioned thread, but only "because they are custom builds." (source)

    Tube amps worthy of consideration that cost more than $1,200 include:

    Solid State Amplifiers for HD650
    The general consensus for the best value solid state amplifier for the HD650 is the Schiit Jotunheim.


    Some other solid state amplifiers worthy of consideration for the HD650 include:

    Additional HD650 Amplification Resources
    We intentionally did not add a separate section about sources/DACs to the FAQ section of this Compendium. This is because:

    For more information on sources/DACs, please see these threads:
     
    Last edited: Jun 13, 2017
  5. zonto

    zonto Friend

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    MODIFICATIONS

    Shoutout to @k4rstar who prepared the very helpful HD650 mod index post and saved me lots of work. Significant portions of that post were integrated into this and the following post(s) re: modifications. Reference is also made to @philipmorgan's preliminary index.

    Overview
    As described by @Marvey here, the most often recommended HD650 modifications include:
    1. Coin mod,
    2. Rear foam and/or spider cage removal, and
    3. Damper application.
    Note that the first two mods have been around for years (source), whereas the damper mod was "inspired by @Bill-P" from the Changstar days (source).

    On December 6, 2016, @Marvey unveiled his HD650 Keep It Simple Stupid (KISS) mod guide. This mod was developed to address a few perceived shortcomings in the trifecta of mods described above, but both will coexist given different preferences and equipment chains. See (source) ("I also DO NOT perform the quarter mod as I did not find it necessary running this out of the Jotunheim.")

    Each mod is discussed in more detail below.

    Coin Mod
    This mod involves cutting a coin-sized hole in the flat foam pad that covers the portion of the HD650 driver that faces your ears. Traditionally, this was called the "quarter mod" due to the use of a U.S. quarter coin as a model for the cutout. (Solderdude, 23–24 (discussing the "well known 'quarter mod' where a hole is cut in the front foam the size of the open dome (about the size of a quarter) in the baffle")). Some of us prefer to use a smaller coin, hence the rename of the mod.

    @Marvey's coin mod (source)
    [​IMG]

    @zonto's coin mod (source)
    [​IMG]
    Objective
    "In the higher frequency plots, [the coin mod measurements] show that the treble response above 5Khz is up to 2dB higher in amplitude." (Solderdude, 23–24 (displaying measurements of stock foam vs. quarter mod including logarithmic and linear scale frequency response, square-wave response, and impulse response)) "The difference between normal foam and foam-with-hole shows somewhat in impulse response. Also there is slightly more 18kHz 'ringing' when the foam has a hole in it (the third 'wiggle' after the falling edge)." (Ibid.)

    See Solderdude, page 31 for measurements and discussion of both the rear foam removal and coin mod, as shared by @jowls here.

    @dllmsch measured the stock Sennheiser and AKG K240 foam pads, each with and without coin mods, on an HD650 with plastic spider cage removed and Dynamat added, as shown below (source).
    [​IMG]

    Subjective
    Think of this as removing a speaker grill. "A bit more clarity is the result." (Solderdude, 23)
    "A possible disadvantage of this mod is the exposed driver dome. Protection against dust, hair or other objects for instance is absent. The 'gain' in clarity may be worth the risk though." (Solderdude, 23) If you need to remove hair, etc. from the driver, blowing or using compressed air may cause driver to crinkle, but this can be likely be fixed by blowing from the back. (source)

    This mod is easily reversible, however, as one may simply replace the front foam pads if results are undesirable. See "Frequently Asked Questions—Pads—Purchasing: How much do stock pads cost? Where do I buy them?"
    The traditional recommendation was a U.S. quarter. Most of us used a U.S. nickel or New Zealand 10 cent coin.
    Solderdude measured the HD650 without the front foam pad and described the changes on pages 19–20 of his treatise:
    • "[ S ]omewhat less damping in the 2Khz range and 13kHz area."
    • "The frequency response between 13Khz and 20Khz is lifted by about 2dB."
    • "The resonance behind the pulse is slightly less damped (lingers on slightly longer) and shows more high frequency ringing (18kHz)."
    • "The trade-off is slightly more high frequency response versus slightly less damping."
    Complete removal of the front foam is not popular here.

    Rear Foam Removal
    This mod involves removal of the foam discs directly behind the driver that damp the driver. There are usually two or three foam discs held in place by the plastic "spider." "The stock HD650 has three foam discs sandwiched together very tightly. Too much damping for my preferences." (source)

    @Marvey's rear foam removal (source)
    [​IMG]
    Objective
    Solderdude measured the HD650 without the rear foam discs and found that "[a]bove 500Hz nothing much seems to change." (Solderdude, 29–30 (displaying such measurements, which showed "[n]o differences in the CSD from 500Hz to 22kHz" and slight changes to the CSD "from 20Hz to 1Khz")). "The removal of the foam affects the frequency range between 40Hz and 400Hz only. You gain a good 1dB of extra bass. Subbass is not extended though. The CSD shows just a slight change in damping not much to worry about. The harmonic distortion differs slightly when the foam is removed. The square-wave response shows a slight tilt to the warmer side of things." (Ibid., 46)

    See Solderdude at 31 for measurements and discussion of both the rear foam removal and coin mod, as shared by @jowls here.

    Subjective
    "[ S ]lightly elevated bass response." (Ibid., 30) "It's a bit like turning up the bass about 1 notch or driving the HD650 via a 120 [ohm] amplifier (compare to the plots on page 12). Not a dramatic change[,] but noticeable none the less and does not seem to degrade the sound. . . . When you want a tiny bit more bass, (more fun sounding, less analytical) removing the foamy will do just that. More accurate/linear it is not. Pick your poison." (Ibid., 46)

    "Removing the foam also exposes the hole towards the business end of the driver. Dust can get in a lot easier when the foam is removed." (Solderdude, 46) "From an amp with low source impedance / lower power, bass control will also be diminished. Can we say blub blub blub?" (source)

    "This mod should be reversible if you are careful." (source) Note this is easier said than done as one would need to carefully "thread" the foam discs back in and pull them evenly with tweezers to fit within the plastic spider.

    See "Spider Cage Removal" and "Damper Application" below for more information on options for retaining damping and adding damper to the magnet. See also "Alternative Rear Damping Strategies" below.

    Spider Cage Removal
    Concurrently with the rear foam removal, many SBAFers also remove the plastic spider cage. The spider cage's function appears to be limited solely to holding the rear foam discs, and to a certain extent the magnet, in place. See "What are the disadvantages? Is this reversible?" below.


    See also
    (source); (source); (source).

    @zonto's rear foam and spider cage removal (source)
    [​IMG]
    Some are of the opinion that removing the plastic spider cage reduces unwanted reflections of the unimpeded rear wave that were causing some harshness and/or fatigue with only the rear foam discs removed.

    See also
    (source); @TRex's spider cage removal impressions.

    Removing the plastic spider cage also allows one to damp the entire magnet. See "Damper Application" below.
    One disadvantage is that "once the spider is removed, there is no place to secure damping material." (source) "It turns out that depending upon temperature or related atmospheric conditions, the magnet can actually fall out of the housing." (source)

    This may be remedied by "us[ing] double sided Dynamat like material cut into a donut and affix[ing] felt on the outer side." (Ibid.) One may also secure damping on top of the magnet or damper placed thereon by using blu tack or little pieces of damper material rolled up.

    Spider cage removal is irreversible, unless you get creative and hack it by supergluing the tiny ends of the plastic spider "legs" that used to connect the cage to the plastic ring surrounding the magnet.

    Damper Application
    This mod involves applying strips of a damper like Dynamat Extreme or Second Skin Damplifier Pro to targeted locations on the HD650 housing and/or magnet.

    Chronological Evolution of @Marvey's Damper Placement

    @Marvey's initial Dynamat mod (source)
    [​IMG]


    @Marvey's subsequent Dynamat mod (source)
    [​IMG]


    KISS mod damper placement (green is recommended, red is unnecessary or has minimal effect) (source)
    [​IMG]

    Miscellaneous
    Community standard damper application, as performed by @zonto (source)
    [​IMG]
    [​IMG]
    Objective
    Damper application results in a measured reduction of bass distortion. See HD650 Dynamat Mods - Proof That It's Not BS.

    Subjective
    See @bixby's impressions here (too long to quote)
    With damper applied, the headphones will be slightly heavier. Damper strips are easily removed (they are like pieces of tape); however, due to the sticky nature of the butyl or similar material, some black residue may remain or transfer to surrounding areas of the headphones, particularly in warmer climates and dwellings. (source)
    Dynamat Extreme
    The most common product used is Dynamat Xtreme. Only a few square inches of product (see source, last image) are necessary to perform the damper mod, so a small amount like the speaker kit (see also UK version) or license plate kit will suffice. Note the difference between regular Dynamat and the thicker "Xtreme" variant. The latter is a more effective damper. Local car audio shops may have scraps they will sell you for cheap.

    Second Skin Damplifier Pro
    Second Skin's Damplifer Pro is a more effective damper and mass loader than Dynamat Xtreme. See (source); (source). Additionally, it is uniformly black (as compared to Dynamat's gawdy silver text). Second Skin sells a U.S. sampler pack and an international sampler pack, as well as "CLD Small Project Computer or Headphone Mod 3" x 5" Sheets." The 3" x 5" sheets were likely added to the storefront due the influx of sampler pack orders for headphone modding. @zonto has personally spoken to Second Skin on the phone about ordering Damplifier Pro specifically for headphone mods. @James Whiting directly compared Dynamat Xtreme and Damplifier Pro and subjectively preferred the latter. (source)

    Miscellaneous
    In addition to the images in "What does damper application entail?" above:
    • These posts show you where to place damping materials with the spider cage intact --1 / 2 / 3 / 4
    • These posts show possible damper placements with the spider cage off -- 1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10 / 11 / 12

    Covering Holes with Damper

    More @Hands impressions here


    Distance of Damper from Rear Vent

    There has been some discussion of whether there should be a gap of a few millimeters between the edge of the driver's rear vent and where the damper donut begins. See discussion in this thread ("I think there is a difference, mainly from there being more material on the magnet damping the driver more." (source)).

    Recent Damper Placement Discussion

    The community continues to refine the mods and has been discussing very precise damper placement questions, sparked by a question from @songmic here. See responses here by @Dino and here by @joeq70 (arguing that an alternate damper placement performed by @SoupRKnowva here sounded best). @songmic response.

    Some discussion of doubling-up damper here.
     
    Last edited: Jun 13, 2017
  6. zonto

    zonto Friend

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    MODIFICATIONS, cont.

    Selected SBAF Subjective HD650M Impressions


    Additional Impressions
    (in alphabetical order by username)

    Modification Tutorials

    Additional Modifications
    In addition to the main community mods, below are resources about additional HD650 modifications.

    Some, like @Hands, prefer to replace the entire front foam disc with the AKG K240 foam disc which is thicker and has a fabric backing. Most perform the coin mod to the K240 pads, as shown in @zonto's image below (source).

    [​IMG]

    Objective
    Solderdude measured the HD650 with AKG K240 foam pads. (Solderdude, 25–26) "Interestingly in impulse response and square-wave response the K240 foam seems to perform slightly better than stock foam . . . and also shows a small increase in speed and upper frequency response while proving even better 'protection' than the original foam." (Ibid.) But see @dllmsch's measurements of the AKG K240 foam which show less treble response.

    Our collective experience seems to favor @dllmsch's measurements vs. Solderdude's. (source); see subjective impressions below. But see @GettingBuckets claiming K240 pads made his HD650 leaner.

    Subjective
    Solderdude
    Solderdude experimented with alternative rear damping materials, including (with page numbers):
    • AKG K240 foam (40),
    • 2mm felt (41),
    • densely packed fiberfill (42),
    • densely packed cotton (43),
    • glass-wool (44), and
    • double the amount of stock Sennheiser foam (45).
    Solderdude summarized his rear damping findings on pages 47–48 of his treatise.

    KISS Mod
    See the HD650 KISS mod thread for discussion re: using Sennheiser stock rear foam discs to damp the driver differently by slightly depressing a crescent fold of such foam into the vent.

    Arctic Cotton

    Our own @gurubhai has experimented, including on @Koth Ganesh's pair, with a product called Arctic Cotton, as recommended for modding other headphones by Head-Fier "nick n." @gurubhai used one (Indian) quarter-sized disc of single layer Arctic Cotton, just "enough so that it fits inside the spider on its own." (source) See more explanation from @gurubhai in the KISS mod thread.

    @Koth Ganesh's picture of the mod (source)
    [​IMG]


    @Yeskey compared bamboo/polyester Arctic Cotton to the KISS mod with measurements here. They did not like the effect of the crescent fold of Arctic Cotton and reverted to a modified KISS mod. (source; see posts that follow for explanation of mods and links to additional images)

    Miscellaneous
    Championed by @Garns, particularly on "the outer rim around the back of both drivers (leaving the silver screen and magnet uncovered). See (source); (round two). Garns used Second Skin's Luxury Liner product, which is a 1/8" massloaded vinyl that comes in the U.S. and international sampler packs discussed in the "Damper Application—Which damper product should I use?" section above.
    Some users like to place a cutout of drawer liner underneath the front foam for additional damping, per @FlySweep's image (source)
    [​IMG]


    Impressions

    We use this drawer liner, available on amazon.com. Credit: @philipmorgan
    Solderdude measured the HD650 with and without grills, but measurements were inconclusive. (Solderdude, 38–39 ("Of course, reflections from the rear will not easily be seen on any plot . . . ."))

    This mod is not recommended due to lack of meaningful sound quality improvement and loss of protection.

    Miscellaneous
     
    Last edited: Dec 29, 2016
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  7. zonto

    zonto Friend

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    [reserved]
     
  8. zonto

    zonto Friend

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    Note: The remainder of the thread from this post onward contains preliminary feedback discussion from when this Compendium was in its draft stages in the Club Room subforum. Trying to get it cleaned up, so please disregard for now.

    Friends,

    I'd like to open this up for responses / feedback now. This is not in "final" state as I need to conform formatting and do clean-up. I feel comfortable with this as an initial draft for community review though.

    FYI: My plan would be to transfer only the relevant compendium posts to a separate, pinned thread in the Headphone subforum once the community is signed off. As such, our posts from this post onward will either be deleted or remain in this work-in-progress thread.

    Potential topics for discussion:
    • Do we want to add a poll? (HD650 vs. HD650M; HD650 vs. HD600; probably too nuanced to get into specific mods). Would it work to bifurcate if we did a two-vote option or would people just abuse it? May be unnecessary for a Compendium.
    • Anything I missed? My goal was to be comprehensive enough that a user could use this as their sole resource and not muddy up threads unless the question wasn't answered here.
    • Is this usable from both established members' and guests' perspectives?
    For those that don't know me, my background is in technical writing so you won't hurt my feelings by giving constructive feedback here. Feel free to PM me if you're not comfortable posting here.

    Thanks,
    -zonto
     
    Last edited: Dec 13, 2016
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  9. Ryu

    Ryu Friend

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    I would like to take credit for the HD650M title. I've been following this for a while now and I think this is probably the best write-up I've seen. The only suggestion I can think of is maybe adding a section for amp and DAC parings?
     
  10. zonto

    zonto Friend

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    Shoot me a credible source and your wish may granted if the timeline checks out.

    For amps, see the last FAQ post: http://www.superbestaudiofriends.or...ennheiser-hd650-m-compendium.3188/#post-94646

    DACs could be an oversight on my part. I tend to think of them as something you buy the best you can afford and shoot for relatively neutrality, whereas I think of the headphone and amp as a unique pairing. Thoughts for resources other than the DAC chart if we add a DAC FAQ? (Don't have the energy to cull the main threads again for DAC nuggets.)
     
    Last edited: Dec 13, 2016
  11. Dino

    Dino Friend

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    @zonto - If we see something that might require your attention, would you prefer we post them here as we discover something or would you prefer we post after we have gone through the entire compendium?

    For example, this link seems to have changed:
    HD600 Instructions for Use

    https://en-us.sennheiser.com/global-downloads/file/4640/HD600_560026_1114_EN.pdf

    404 Error
    The requested page could not be found

    This seems to be the link now:
    https://en-us.sennheiser.com/global-downloads/file/4640/HD600_Manual_11_2016.pdf


    I'm just getting started and ran across this. I could keep all for one post or post as I find something.

    Great job, btw!
    ____________________________________________________________________________________________
    12-5-2016
    Under - "Spoiler: New vs. old pads?"

    See Solderdude at 4 (showing measurements of new vs. old pads). - Wondering if there was supposed to be a link here.
    ____________________________________________________________________________________________
    "Both the frequency response, distortion plots and above all square-wave and impulse response plots show how 'warm', bassy and 'slow' the HD650 with older pads is." Id. at 13–14 (displaying aforementioned plots).

    The link "at 13–14" is getting an error.
    ____________________________________________________________________________________________
    Under -
    "Spoiler: Stock or third-party pads?"

    Solderdude at 15. - Wondering if there was supposed to be a link here. Maybe the "Solderdude at #" are place holders of maybe something that I don't understand.
    ____________________________________________________________________________________________
    Id.
    at 15–18

    The link "at 15–18" is getting an error. Wondering if the "Id. at #-#" is a place holder.
    ____________________________________________________________________________________________

    Okay. I am getting it now. The Solderdude at #. it is the page number(s) of his pdf.
    http://www.mediafire.com/view/d9kb768up61eh3b/HD650_modifications.pdf


    So it is only those two links: "at 13–14" and "at 15–18".
    ____________________________________________________________________________________________

    Left off on:
    MODIFICATIONS
    Spoiler: What about removing the entire front foam pad?

    I'll check some more tomorrow.
    ____________________________________________________________________________________________
    12/7/2016

    MODIFICATIONS, cont.
    Selected SBAF Subjective HD650M Impressions
    Spoiler
    Additional Impressions

    @James Whiting (search results for his username in the main thread; his chronicle is too long to link directly)

    Clicking "search results" returns "The requested search could not be found."

    This link works: http://www.superbestaudiofriends.org/index.php?search/3172959/
    ____________________________________________________________________________________________

    Spoiler: Drawer Liner
    Some users like to place a cutout of drawer liner underneath the front foam for additional damping, per @FlySweep's image (source)

    There is no link for "source".
    ____________________________________________________________________________________________

    Done.
    ____________________________________________________________________________________________

    The quantity and quality of your work on this -
    I don't know how to describe how impressive that was, @zonto .
     
    Last edited: Dec 7, 2016
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  12. zonto

    zonto Friend

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    Thanks for the kind words and your help!

    Whatever is easiest for you. Hyperlinks and hosted images will probably have those issues often. Noticed one today myself...

    Maybe keep a running list in your post above and let me know when you've made an initial pass through? I can then update links, etc. in one pass.
     
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  13. Dino

    Dino Friend

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    Sounds like a plan.
     
  14. zonto

    zonto Friend

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    Your comments above are implemented.

    Good catch on the manuals. Sennheiser updated both the HD600 and HD650 manuals in November 2016, replacing the November 2014 versions I had previously cited/referenced. Notably, they changed the specified frequency response for both headphones, so I left the old ranges in a subbullet in the relevant Specifications spoilers above.

    Interestingly, the HD600 manual entries for Connector, Adapter, and Connection cable are now identical to the corresponding HD650 manual entries. If this was intentional, there is a possibility that new-production HD600s could ship with the HD650 cable and 1/4" to 3.5mm adapter.
     
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  15. zonto

    zonto Friend

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    Thanks for your help! All your edits are implemented. The James Whiting search results link changes every time, so I just posted instructions to search instead of linking. Also added a new "Note re: Sources" spoiler at the end of the Amplification section based on @Ryu's comment above. That and the System Synergy thread linked should be sufficient for our needs here.

    All, any other feedback, particularly on the three questions asked above, or is this ready to go (once I add the KISS thread in)?
     
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  16. Dino

    Dino Friend

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    Looks good to go, as far as I can see.

    Thanks for putting a (very) few things to catch. Otherwise, it would have been boring. :)
     
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  17. purr1n

    purr1n Finding his inner redneck

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    Thanks for the effort. There is also the KISS mod now, which is what I use.
     
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  18. aufmerksam

    aufmerksam Friend

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    Holy shit dude, this looks awesome. Are you home with a babby by any chance?
     
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  19. zonto

    zonto Friend

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    Thanks! And yep. Naps are the only reason I had the time to work on it so much recently. :) Go back next week.
     
  20. Dino

    Dino Friend

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    If you guys think it looks impressive, wait until you go through it - wow!
     

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