Jupiter Audio Research "J-Mod" (HD650 mod)


1000+ Head-Fier
Pros: Increase in detail retrieval, tightening of the bass, no 'Sennheiser veil, attractive design
Cons: Some of the same HD650 complaints still apply. Headband clamp force, sub bass roll off

The Sennheiser HD650 has been a standard for audiophiles since its introduction 14 or 15 years ago. Because of its already stellar sound as well as being relatively easy to disassemble, the 650 has also been a staple for headphone DIYers everywhere. The JAR650 (JAR stands for Jupiter Audio Research) is one of the newest takes on a HD650 mod, but this one isn’t geared toward the DIY community so much as those looking to maximize the sound of their 650 or anyone looking to buy one of the best sounding headphones I’ve heard.

(Photo courtesy of Jupiter Audio Research)


Although Jupiter and I have been friendly over the past 1 ½ years or so, I have not (to my knowledge) let that friendship unduly influence my review. We are in negotiations for trading my HD600 for an older prototype of the current JAR650. I can honestly say that after hearing Jupiter’s end product, the review would have happened regardless, and I would have more than likely saved up for my own JAR creation.

Meet the maker

I met Jupiter (the brains behind the JAR650, AKA the J-Mod) online here on Head-Fi. He bought a couple of headphones from me back in November of 2016, and we have kept in touch ever since. When I first heard Jupiter talking about his modded 650, the passion he communicated with was readily evident. He was constantly working on it, tweaking it until the sound was just where he wanted it. Once I got to hear the end result, I finally understood.

I don’t know the whole story, but I do know that the creation of the JAR650 has been a long and arduous journey for Jupiter. He is an engineering student and like most of us here on Head-Fi he loves music. Unlike many he has had the good fortune of owning and enjoying several of the TOTL headphones on the market including Utopia, HD800, and Stax (007 &009). As much as he’s enjoyed them all he always found something to nitpick about and so started where many modders do: The HD650.

The HD650 as a standard

It’s time to give credit where credit is due. Jupiter was kind enough to lend me a stock HD650 for comparison, and I feel it’s safe to say that the HD650 is a fantastic headphone in its own right. There are multiple reasons that this headphone is a classic, and I am very glad I got to spend time with it.

This Senn may be the best known headphone to dance the line between smooth & resolving. A mid-bass bump, and gentle, perhaps slightly rolled off treble were more than likely keys in coining the term ‘Sennheiser veil’, but the details in the music are all there. It should be noted that a good amp is a requirement for getting maximum aural pleasure(which also holds true for the JAR650). Thankfully there is plenty of pleasure to be had with the stock 650.

-The midrange is absolute magic giving vocals and acoustic instruments life.

-The bass is definitely rolled off below 100 Hz or so, but the bass that is there is punchy without being overbearing.

-Soundstage or headstage is not considered to be a strong suit. It is considered more intimate in size, however imaging is quite good.

Either in spite of or because of all these traits, the 650 remains one of the most beloved headphones on the market today, and is a thoroughly enjoyable listening experience. Sennheiser definitely did a lot of things right with the driver and tuning of the HD650.


All listening was done from my JRiver Media Player on my HP all in one PC feeding a mix of high rez and MP3 files to a Schiit Gungnir D/S into either an ifi iCan Pro or a MCTH with the stock tube. Like the HD650, the J-Mod sounded great through both SS & my hybrid tube amp each bringing its own flavor to the already stellar sound.

The physical headphone

Like all 650 mods there are various parts removed from the stock configuration and dampening applied to key areas. What parts are removed as well as the location and material for dampening vary from mod to mod, but the basic idea is the same: make sure what you add doesn’t take away from the sound. Jupiter tried several of the various mods, but still walked away dissatisfied. Over a period of months, he used trial & error to zero in on the sound he wanted. He also developed a novel idea that I haven’t seen used before. He created 3D printed part for the back of the headphones. This has the dual purpose of further tailoring the sound as well as adding some rear protection. For me, it’s also an aesthetically appealing feature. It’s a shame he wasn’t able to address the clamp of the headband, but he could hardly be considered at fault for that. A new headband would also likely increase the price considerably.

The differences

Personally I have never attempted to mod a headphone beyond adding a filter (TP mod!) or pad rolling, so I don’t know how hard or easy it would be to mess up the venerated stock HD650 sound. I do know there are a variety of mods available, although I haven’t heard any of them up until now. If I had never heard the JAR650, I would be quite happy with a stock HD650 in my collection.

It seems to me that the object of modding any headphone is to tailor the sound to your tastes which is therefore a subjective affair. Obviously, what is a sonic step forward for me may very well be less enjoyable for you. That being said what Jupiter has done is take a classic headphone and worked on evolving the sound into something I find to be all together even more engaging than the original. I’ll do my best to describe the differences.

Starting down low, the bass seems tighter to my ears, but no less impactful. The stock 650 has a loose quality to the bass. Although the Stock bass is punchy, I do hear a smear to the sound of an upright bass, maybe a touch too long in the decay of notes. The JAR has a bit more snap in the bass. The punch is still there but it’s quicker. The bass is still rolled off so there’s no miracle here but as with the stock 650, I didn’t miss it at all for most of my listening.

Thank goodness the mids still sound magical to me. If anything they are even clearer, without edging anywhere close to shouty or strident. If I was to guess I would say it’s because the bass is tighter, making the information in the mids and treble easier to discern. Whatever the reason vocals, strings et al sound phenomenal through the JAR650.

As I hinted at, I found that the treble was more resolving as well with no audible peaks, spikes or valleys. I was treated to what is, for my tastes, one of the best treble presentations that I have ever heard. While still leaning toward a relaxed presentation, resolution was increased to my ears without introducing harshness. The sound was not aggressive, but still detailed. Cowbells, triangles cymbals all sounded crisper, more of the overtones were easily heard, but the tonality remained true. I couldn’t detect the infamous Sennheiser veil at all.

Soundstage seemed relatively unchanged to me, that is to say relatively narrow. Imaging as well sounded on par if not a little better, but I’m not particularly skilled with observing that. When I put it all together though, I find myself struggling not to dip into the big book of audio clichés. This headphone absolutely drew me into the music like few headphones can. That is what I’m looking for in a headphone. That is what I’m listening to music for.


To be fair, there may be those out there that prefer the more laid back stock 650. That headphone is smoother overall, very easy on the ears and the design has stood the test of time (albeit with some silent revisions over the years). The JAR650 on the other hand is more energetic and lively. The difference is not stark but incremental; however the contrast is there nonetheless. For my tastes, if you can add resolution without harshness and increase my desire to keep listening to the music you’ve definitely done something right. I don’t want to sound too effusive, and it’s been a struggle not to in this review. With that being said if your goal is to better a classic headphone and you achieve that goal, it’s hard not to seem overzealous. IMHO Jupiter has achieved that goal admirably.

The JAR650 is available for $390 (USD, plus shipping)*, and the mod can be purchased for any existing stock HD650 for $100 (USD, plus shipping).

(For further information about the JAR650 contact @ext1 on Head-Fi)

*Edit: Price quoted was at the time of writing, apparently current retail will vary.
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Just an update for people interested: I was looking into the Jar600 for existing stock, and was quoted a price of $550 for modding my existing hd600. As the price has changed since the posts I thought it would be good to put the update.


Headphoneus Supremus
Pros: The higher-resolution, dynamic, tonally accurate upgrade to that great HD650 sound
Cons: Not a single thing
Over the past year or so, I heard 3 iterations of extensive HD650 mods from Jupiter Audio Research (the "JAR-650," aka "J-Mod"). A month ago I received the finalized J-Mod that is the subject of this review, plus a stock HD650 for comparison.

I'm late getting to the Sennheiser HD650 party. It's easy to see why so many love this headphone. Had I not heard the J-Mod, I could happily live with the stock headphone. It's voiced perfectly for my tastes and scales up readily with better sources. And as my review of the J-Mod will show, it has considerable potential for even better sonics.

Regarding mods: Modding HD650s is a major indoor sport in the headphone community. I'm not very familiar with any of those mods: I haven't heard any, also haven't done any myself. I do know certain elements of known HD650 mods are used in the J-Mod—ie, removing the inside foam layer covering the driver; removing the dome covering the driver's outside center. Nevertheless, the J-Mod is more extensive and ambitious than any discreet mods I've heard of:
  • The stock grill is replaced with a proprietary, 3D-printed, custom-damped, dimensional screen
  • Internal damping is added and some stock materials selectively removed from each earcup
  • Each physical element of the J-Mod has been rigorously/repeatedly auditioned & adjusted for best sound (over a period of several years)
The J-Mod represents a true evolution of the HD650--a complete re-imagining & re-voicing of the stock headphone.

Disclosure: I paid market rate for my J-Mod & have no business relationship w/Jupiter Audio Research or this mod.

Jupiter Audio Research has agreed to a loaner program for the J-Mod: the pair I purchased and reviewed will be available for loan to other reviewers. That pair is already with one reviewer; as soon as it's returned, it will be available for review by any Head-Fi members in good standing & who are interested in the next step in the evolution of HD650 sound.

Please PM me for details (@Pharmaboy).

Note: My J-Mod is now with a 2nd reviewer; and a third reviewer will get the loaner as soon it's back with me.

Jupiter Lee of Jupiter Audio Research is an electrical engineering student whose experience with high-end headphone audio goes far and deep. His listening journey began with IEMs, then a succession of closed-backs, then the HD650, LCD-3, Atticus/Eikon, Utopia, and 007/009 electrostatics. He was impressed from the start with the stock sound (and modding potential) of the HD650, and so began a long development process to re-voice its sound, resulting in the current J-Mod. Jupiter employed the Hugo TT and Violectric V281 in balanced mod for the J-Mod development, an empirical process that took several years and involved countless design iterations, as well as many listening & soundcheck sessions.

I'll get right to the point: the J-Mod sounds amazing. I was unprepared for how compelling the J-Mod is. My usual J-Mod experience went like this: put them on, get lost in the sound--then have trouble taking them off.

The J-Mod changes the stock headphone's sound for the better in multiple ways, all positive (details below). I can't hear any downside to the J-Mod. The stock HD650 already has impressive sonics, and the J-Mod takes it across the finish line into near-endgame territory (surely as close as one could hope at this price). I definitely prefer the J-Mod over stock.

The J-Mod is strongly recommended. Choosing the J-Mod over stock is a true no-brainer IMHO.

Figure 1: J-Mod

Black mod NEW-1 (resize + GAMMA adj).png

Figure 2: Stock (left) vs J-Mod (right) – inside view
cup vs cup (inside RESIZE).jpg

Figure 3: Stock (left) vs J-Mod (right) – outside view

cup vs cup (outside BEST).JPG

Figure 4: Stock (front) vs J-Mod (back) – Side View

cup vs cup (side view - 200% + GAMMA corrected).png

As many of you already know, the stock HD650 is a somewhat bassy, warm, yet relatively articulate & resolving design. There's little or no sub-bass. The midbass has a "hump" and bleeds into the mids somewhat. The midrange is the star here, carrying most of the information (in a musical fashion). Then comes the well-known "Sennheiser veil" in the upper mids/lower treble, and to my ears, a drop-off in the treble (which sounds pleasing, but really isn't the main action).

What does the J-Mod do differently vs stock?

1 – Better damping: The single biggest difference I hear between the J-Mod and stock is the near-complete elimination of reverberation, note-blurring, and other time domain sonic anomalies. As pleasing as the stock headphone sounds overall, after hearing the J-Mod I realized stock is somewhat under-damped and reverberant.

2 – Resolution & clarity: Considerably better in the J-Mod, in part because of better damping. Notes stop and start quickly & with authority, almost as planar drivers do. On the J-Mod I can more easily/clearly hear subtle spatial/ambience cues, reverb "tails" & sounds buried in the mix. I wouldn't hesitate to recommend the J-Mod for studio monitoring (not something I'd recommend for stock).

3 – Dynamics/"jump factor": With reverberation under control in the J-Mod, dynamics take a leap forward. This is lively, exciting headphone audio, far more so than stock. The J-Mod really nails dense/multi-tracked music such as well-recorded studio rock/pop, hip-hop, reggae, Afropop, Latin jazz, R&B. And with those old sonic standbys for the stock headphone, acoustic music and classical, improved dynamics produce a seemingly uncompressed, life-like representation of the original venue.
  • I have some smokin' hot Latin jazz tracks w/brisk tempi, dense rhythms & multiple/layered percussion parts. Those tracks are killer on the J-Mod: instruments seem to pop out of nowhere, and percussion surrounds my head in a precise, well-spaced array (see "Soundstaging" below). Sometimes it's hard to sit still when listening the J-Mod, not something I can say about stock.
4 – Soundstaging: The strong basic capability of the HD650 driver is the key here. Both stock & J-Mod have soundstaging of the "intimate/defined" variety (vs huge & spacious). But with the J-Mod's flatter, less reverberant sound, soundstaging is even more precise & exact (ie, this instrument is right there & that one is right here). The soundstage is close to my head, but it's so precise that, especially with multi-track recordings, there's quite a lot of side-to-side soundstage movement. IMO soundstaging is a strength of the stock HD650, and the J-Mod makes it even better.

5 – Tonality: The stock HD650 sounds to me like a gentle, upside down "U"-shaped curve, with falloff at either end and slight elevations in the midbass & midrange. By contrast, the J-Mod sounds level: the mids are excellent, yet there's more/better performance in the bass and treble. Thus the J-Mod sounds flatter, more precise & controlled--yet not hyped or tiring. Instrumental and vocal timbre really comes through on the J-Mod--again, aided by its reduction in resonance and resultant colorations.

Bass: I like the stock bass, but the J-Mod's bass is definitely better. It seems to hit a little harder and go a bit lower; pitch definition & resolution are notably better. The J-Mod more accurately tracks the bottom registers of every kind of music I played on it. In line with the relatively flat & honest voicing of the J-Mod, there is no apparent bass bleed into the midrange. The J-Mod's bass was a pleasant surprise for me. Except for sub-bass, I find it to be competitive in nearly every way with more expensive designs.

As with the stock headphone, the mids are the star in the J-Mod, but with improved clarity, resolution, and dynamics. Unlike stock, there's little or no bass intrusion into the mids. On the J-Mod, the mids are detailed, rich, and musically satisfying.

The J-Mod's treble is just about the best I've yet heard from a headphone. It's incisive and detailed--yet not bright or fatiguing (a neat trick). When listening to large scale orchestral music, for example, it's easy to hear the violins soaring high above the cello and brass sections. This is an open, clear treble. I have no way to measure the J-Mod, but I'd surprised if the treble wasn't a relatively straight shot w/no significant up or down spikes. This excellent, involving treble perfectly balances the slightly warm bass & midrange.​

All these positive changes work together to make the J-Mod a very compelling headphone. As much as any headphone I've heard (at any price), it sounds like real music.

  • Burn-in: The J-Mod definitely benefits from burn-in. I burned it in for ~80 hours, and during that time, the bass and lower midrange deepened and became more present—a perfect match for the incisive, high-flying treble. The resulting tonal balance is just about perfect IMO.
  • Amping: I listened to the J-Mod on 4 solid state amps (V281; LC v2; Lake People G109-A; M Stage Matrix HPA-1); and an OTL tube amp, the Woo WA3. The surprise was that I preferred solid state amps by a large margin. Not sure why, but the J-Mod is amp-agnostic and can sound very good with less-than stellar sources (it sounded fantastic on the HPA-1, my cheapest & least powerful amp). I heard the expected differences between these familiar SS amps, but those differences were not spotlighted by the J-Mod. Balanced cable & amp sounded better than SE, but again, margins were not large.
How does the J-Mod measure up to other open-backs? I wasn't able to compare it to high-end flagships like the HD800, Focal Utopia, ZMF Auteur, or Stax SR009. Those comparisons would be fascinating; the J-Mod may well give these far more expensive TOTL designs a run for their money.

The J-Mod is clearly on a higher level than another open-back dynamic, the slightly less expensive Fidelio X2, which is lots of fun, but less resolving & with more diffuse/imprecise soundstaging than the J-Mod. I also find the J-Mod sounds better in every way than the Onkyo 800A (comparably priced).

At or just below the $1K price-point, though, things get very interesting:
  • I heard the Hifiman Sundara and Beyerdynamic Amiron Home at CanJam (both ~twice the price of the J-Mod). I believe the J-Mod handily outperforms both
  • I also heard the MrSpeakers Aeon Flow Open (a planar that's ~2X the cost of the J-Mod), and believe it's nose-to-nose sonically with the J-Mod (differences being relatively minor)
  • A headphone that begs comparison with the J-Mod, based on similar voicing, is my LCD-2.1, a pre-fazor open-back planar with terrific sound. The two headphones compare quite well in overall tonality, soundstaging, and resolution. The LCD-2.1 has the sub-bass both the stock HD650 & J-Mod lack, and is just a bit better in other ways. Still, differences are rather small; the J-Mod matches very well with this legendary Audeze design
So the J-Mod is comparable to (or better) than headphones costing up to 3X its price. The J-Mod impresses me as a sonic over-achiever that pushes the limits of mid-fi, even getting into high-end sound.

Pricing/Contact Info
J-Mod is the brainchild of Jupiter Lee at Jupiter Audio Research (@ext1 on Head-Fi). Please contact him for quotations and additional information.

The price of a new J-Mod/HD650 is $390 USD (not incl. shipping). Jupiter will mod currently owned HD650s for $100 (not incl. shipping) upon request.

Takeaway: At these prices, there's no good reason to choose the stock HD650 over the J-Mod. Sonically, the J-Mod is a must-have headphone.
Sorry, as of now I have no such plans. I'd have to modify each pair myself because I have to do driver matching.
Very interesting. I assume this mod must be complicated if the HD650 has to be shipped to Jupiter allowing them to do the mod. In other words it's not as simple as removing the screen cover and plunking in this Jupiter insert and then snapping the screen cover back on?
The J-Mod is definitely more complicated than just the things you mention--more comprehensive than any single mods, such as the KISS mod, mentioned here or elsewhere. The J-Mod has also been modified recently beyond the level of the J-Mod I own (based on high-level reviewer feedback). My J-Mod was subsequently updated by Jupiter Lee & still sounds rather amazing to me.