Prelude
When it comes to the TH909, most discussions revolve around two main points:
1: whether the 909 is an upgraded or even "ultimate" version of the 900;
2: whether the sound of the TH909 is much more neutral than the TH900; or even to the extent that it loses some of the distinct characteristics of the TH900.
Regarding the first topic, personally, I don't consider the 909 to be a true "upgrade" or "ultimate" version, because the drivers in the 909 are very similar to those in the th900s. I believe Fostex has mainly made some tuning adjustments, similar to what they did with the Blue 900, White 900, and Purple 900 versions (the Green 900 essentially being a repainted TH900 mk2 Red); or perhaps they've made very minor tweaks.
Driver of TH909
Although marketed as open-back, the TH909 doesn't quite resemble typical open-back headphones, as you can't see the drivers from the outside.
Upon disassembling the TH909, I discovered a dual-layer acoustic material behind the waffle-like outer structure,
isolating the drivers from the outside. The first layer consists of black high-density foam (underneath the white bio cellulose film), topped with a layer of white Bio cellulose film (similar to the paper-like film on the driver).
From this perspective, I don't really consider the TH909 to be an fully opened-back headphone.
Sound
Tuning
The TH909 has indeed, 'compromised' a lot compared to the TH900, TH909 didn't inherit the iconic V-shaped tuning of TH900 series. It leans more towards a neutral and balanced tuning style, although objectively speaking, it's not entirely neutral.
I once owned a TH900 MK1 Red, and I believe it has an issue with the midrange: mids is quite thin, with imaging positioned towards the rear; on this basis, the V-shaped tuning is like pushing the mids way behind the bass and treble, which further encroaches on the mids' existence.
The tuning of the TH909 is like dulling both ends — the highs are no longer piercingly bright, and the lows are no longer overwhelmingly powerful. Though the sound signature remains similar to the TH900, the tuning sets them apart as two distinct headphones. It's like a bottle of aged whisky—no longer harsh and spicy, but rather composed.
The TH909's standout characteristic lies in its departure from the legacy V-shape tuning of the TH900 family.
Soundstage
I think the TH909 and TH900 don't show very significant changes in terms of soundstage; they both have brilliant soundstage with ample spaciousness. Both of them have brilliant horizontal soundstage that is wide enough to precisely demonstrate the separation of instruments, you can distinctly and clearly sense the instrumental placements, with sufficient spacing between each instrument.
I believe the difference between the soundstages of the TH909 and TH900 lies in the vertical dimension. The TH909 exhibits better vertical soundstage, allowing you to perceive more differences in the layout of instruments in depth.
Bass
The bass of the TH909 is no longer aggressive and fierce but appear more 'civilised'.
Bass texture of the 909 is similar to TH900's, with good extension, different layers and decent impact. However, the depth of the bass isn't as deep as TH900 imo, the sub-bass doesn't goes as deep as the TH900. With the TH900, the overwhelming bass always drew all of my attention when listening to EDM tracks, I mean, that cool, that's the point I like TH900 so much, the depth of TH900's bass is like a ’Journey to the Center of the Earth', both energetic and stunning.
One of my favourite EM: Enough Is Enough (feat. Richard Caddock) - Puppet & Cormak
In contrast, the TH909 tends to remind you that '
this part is the bass, and that's it', without drawing your entire attention away . It lacks the TH900's striking bass impact, not that punchy.
Overall, the bass on TH909 has a more cohesive characteristic, especially when listening to rock tracks, the performance of the TH909 is more like the drummer's beats complementing the band's performance, while the TH900 is like the drummer has ‘
knocked out all the other members' and then taking the opportunity to pound vigorously on stage.
Speaking of rock, I highly recommend this one: Come Close - Saosin
In summary, while traces of the TH900's bass characteristics can still be found, there's a noticeable difference in impact and depth.
Mids/Vocal
The vocals have now reached a completely acceptable level. Although there hasn't been a significant increase in mids thickness, the vocal imaging distance has been pushed forward a lot, and, most importantly, thanks to the balanced tuning without peaks at both high and low ends, vocals can now be heard more clearly.
So, with all these improvements combined, vocals have become much more natural. Furthermore, they've become very smooth, without any piercing or harshness at the peak of vocals, although under some circumstances there might be sibilance, it's not overly jarring. Listening to anime tracks won't feel like the highs are piercing your eardrums, and vocals won't sound like they're coming from a distance. It truly provides an enjoyable vocals.
Highs/Treble
When listening to the TH900 previously, I sometimes felt that the treble was way too bright and sharp, to the point where my ears would even ring after taking off the headphone. But now on the TH909, the energy in the treble has returned to a more normal level. It's no longer like a wild horse running unrestrained, reaching to endless high. The tuning of the TH909 is like taming that wild horse, it largely resolves the issue of piercing and uncontrollable treble.
Since the problem of sharpness is no longer present, the remaining issue is sibilance. Sibilance only occurs in a few instances, perhaps only about 1/6 as much as with the TH900, which is within an acceptable degree.
However, in terms of brightness, if you're accustomed to the bright sound of the TH900, you may feel that the TH909 has lost some of its brightness and appears somewhat dimmer. This feeling is akin to painting a light gray coat over a bright white light bulb, resulting in an overall decrease in brightness and a sense of dimness.
Epilogue
Overall, the TH909 makes me feel like it's a product of compromise, a concessions to the market in order to appeal to a wider audience, it's leaning more towards balance though in fact it's not entirely balanced as neutral.
For me, its benefit lies in saving me the trouble and expense of buying mod kits one by one to try out the effect. It achieves a non-fatiguing sound with smooth and forward vocal imaging. However, my biggest regret is that the bass and sub-bass are no longer as impactful and deep as the TH900. If it could retain the bass punchy while achieving this sound signature, I believe I would be absolutely satisfied.
Disclaimer: This review has no commercial intent; but simply to document the sound of the TH909, a distinctive member of the Fostex family that I greatly adore.
