Today marks a week of enjoyment I've had listening to the 616 as well as revisiting some of my old Fostex Favorites
Foster's Biodyna models are storied and renowned in the hobby. The biocellulose driver used has its roots in a historic collaboration with Sony, the MDR-R10, which was the first headphone ever to feature such a driver. The Denon D2000/5000/7000 are classic Foster 1 Tesla OEM variants and were my own introduction to this headphone platform. Although Denon has replaced the design, you can still purchase very similar OEM variants from EMu and likely others.
Foster's in house brand, Fostex, has of course produced a number of their own variants of the 1 Tesla driver, and also some exclusive designs using a 1.5T TOTL version (900/909).
As a headphone/IEM collector, I suppose it makes sense that the best way that I come to understand a new pair is by comparison. Understanding what role the headphone was designed to play, ideally vs a range of its peers is an odd delight for me. With that in mind, as promised it's my pleasure to share some comparisons I made listening to the new TH 616 vs the "Massdrop" TRx Ebony and the TH909:
Left to right: TRx Ebony, TH616, TH909
12th Man, 1 Tesla Soundoff
First off, let’s compare the TH616 to my other 1 Tesla variant, the TRx Ebony. Ideally, I’d love to compare the 616 directly to its closed back sibling, the TH610, but unfortunately my Fostex collection leans quite heavily into the 1.5 T variants, and the Ebony is my only headphone with this driver (other than the new TH616 of course!)... I will admit I am severely tempted to fix this and pickup a matching 610. For science.
Anyway, for context, “Massdrop” (now Drop) collaborated with Fostex in the mid to late 2010s on a line of Fostex/Massdrop branded 1 Tesla variants initially called the “TH-x” that was available in Mahogany, Purple Heart and Ebony shelled variations. Later, in 2018 they released an updated version (similar to the 900 mk2 and 610) that featured a removable cable, called the TR-x (for removable). I was fortunate to get in on the first batch of TRx that got sent out by Massdrop back in the summer of 2018.
(image credit:
https://www.pinterest.com/pin/seattle-area-events--205054589257857450/)
As an aside, In American 11 person sports, particularly US Football, there is a concept of the “12th man” on the team… the fans. The local fandom here in Seattle seem to particularly embrace the concept, and the #12 is reserved for the fans. I may not be much of a Football fan, but I am a HUGE Fostex fan
It was a delight, then, to discover that not only did I get a nice low SN on my Ebony, but that it was fan’s 00012. By pure joyous coincidence, the TH616 I purchased from the first batch is also #12, a perfect match for my 1T Ebony.
The 12th man.
But enough autistic serial number gushing… how do they compare?
In terms of the physical product, there are a number of cost saving measures evident on the TRx model. The cable isn’t Rhodium plated and the hardware is less premium feeling. Although similar in form factor, the material for the headband and pads used in the 616 feels a bit nicer than the variation used on the TRx.
Walnut and Ebony
The tuning of the TRx was actually quite a departure for Fostex' house sound. Massdrop had them put a lot more lower mid emphasis than is typical. At the risk of generalizing, they are a European/American style tuning relative to most of Fostex’s models.
Compared to the 616 there are some dramatic differences. There is a lot more upper mid bass on the 616, although I would say they are similarly extended down low towards sub bass. The upper mids on the 616 seem a little scooped in comparison to the relatively forward and flat mids and treble on the Ebony.
Whereas the Ebony might be as close to a flat “reference” tuning that Fostex has made, the 616 brings a lot of warmth and slam for the extra mid bass emphasis. They are an absolute treat for drums (acoustic particularly, but electronic is good too).
That mid bass presence on the 616 does bleed into the mids a bit, and for lower register vocals it can get into honky territory. In contrast, the forward mids of the Ebony bring vocals forward in the mix, at the expense of some soundstage. In terms of detail, the Ebony’s tuning is more rolled off in the treble (tastefully so) but it can be a bit subdued for what I want from these Fostex. In contrast, the 616 loses some textural detail from the mid bass, which is compensated for a bit by the relatively higher upper mid frequency peak.
The tunings are different enough that I am hard pressed to say I really think one is better than the other, but my own preference for what I want from this driver definitely aligns more with the 616. Still, I am very keen to get some exposure to the 610 which I think would be a stronger comparison.
Open Season, 616 vs. 909 in The Palindome!
(photographers note: don’t have to worry about getting caught in the cup reflection nearly as much with these!)
Fostex began exploring open back designs with the TH909, released back in the summer of 2018 (it was an expensive year for me lol). They lopped off the beautiful top of the 900’s Urushi cup and replaced it with a dual layer arrangement of metal for “diversified resonance” - in addition to reducing cup resonance, the dual features on the layered grill allow the introduction of deliberate counter resonances for tuning purposes (think of it as the reverse of the helmholtz resonator Sennie uses).
The shared lineage with the 616 is visually evident. Fostex has used a similar layered grill approach here, although this time it is lovingly carved from walnut to match the housing. The new English pre-order copy words the approach quite nicely:
This precision-machined design not only upholds structural rigidity but also effectively eliminates the generation of modal vibrations. Each opening is meticulously sized to prevent resonance at particular frequencies.
Internally, the 909 uses the TOTL 1.5 Tesla Biodyna as the TH900, so some performance differences could be expected there.
The pronounced mid bass of the 616 is again a defining differentiator compared to the TH909. While I would say the 909 might come out ahead slightly in sub bass, there’s clearly more energy in the mid bass from the 616.
That mid bass energy is felt elsewhere in the tuning as well. Whereas the relatively scooped mids of the 909 highlight the rapid transient response and resulting decay texture, the initial impact slam dominates on the 616. Whereas the 616 sounds organic and warm, the 909’s detail and tight mid bass result in a thinner sound.
Perhaps the other biggest contributor to sonic differences between the 2 is the pads to be honest. The 616 has a much more ear covered pad, almost on-ear, whereas the 909 is more like the TH900 cups and creates a volume of air around the ear. Where this impacts most to my ear is in the sound stage size.
The 909 sounds much wider (similar to the 900), but some of that width can begin to get a bit sparse. The 616 (and TRx) are comparably more intimately staged, but the imaging capabilities of the driver produces a wonderful gradient with what is there. Comfort wise, for my larger ears at least, the 909’s pads are way more comfortable.
Conclusion: I Need to Spend More Money 
Sorry wallet, that 610 looks mighty tempting… there’s nothing I like quite as much as a good open back and closed back pair of pairs.
Either by virtue of the collaborative tuning or substantial pad difference, I didn’t find these comparisons as useful as I had hoped and have sat for a while trying to qualify my findings. All 3 headphones although sharing a high degree of design DNA have substantially different tuning approaches.
My gut is telling me that with the 616, we are looking at a slightly more v shaped take on the well regarded 610 (particularly more mid bass!), but I need to listen and confirm.
Regardless, I will not be surprised if the 616 continue to dominate my ear time this coming week. I find the bassy, warm organic profile highly pleasing for a number of genres in rotation, but particularly have me returning to Jazz Fusion. It just captures the joy, the artisanal love in these headphones so well. Funk and bass guitar heavy music is particularly flattered by these headphones.
While my credit card recovers enough to consider splurging on a 610, I think I will compare next to the TH900. I wonder in particular if the lovely mid bass of the 616 might be pronounced enough to win out there vs. the bass beast… in any case I am thinking a comparison with another more v shaped tuning would help me understand the 616 more.
Hope it was entertaining if not useful, Fostex Fam!
Understandable. Congrats. Waiting on your impressions and comparisons.
