TH-X00 Mahogany (Drop)

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Published: Feb-11-2017

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NO SMOOTHING is applied to the shown plots. Most measurement sites have some smoothing applied which ‘irons flat’ sharp peaks and ‘wiggles’. I do not use smoothing because some info about sound quality is lost when plots are smoothed.

Aside from a small correction of the microphone itself also some correction in the lowest frequencies is applied to the plots to compensate for the perceived loss of bass when using headphones. This is described HERE in more detail.
A ‘horizontal‘ frequency response curve on the shown frequency response plots on this website thus indicates a perceived ‘flat’ tonal signature.

ALL measurements are made with a good SEAL on a flatbed measurement rig.
shape of your head, bone structure, pad size, pad ‘softness,  (compliance), hair or no hair and or wearing glasses may (drastically) change the frequency response of some headphones, so… your personal experience may differ substantially from these plots.

Frequency response (tonal balance) is the most sound-determining aspect of headphones. A horizontal line shows audible neutral response in the plots on this website. Deviations in different severities at different frequency bands have an effect on the sound character.
The bigger the deviation the stronger the effect.

Below an aid to help determining the sound character of headphones with relation to the frequency response.


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Fostex TH-X00 (Mahogany)


This is the Drop® Fostex TH-X00. The build quality and comfort is high. The cups are made of mahogany wood. It has 50mm (Tesla)drivers with a Biocellulose membrane/cone. Foster is the company that manufactures drivers and headphones for several companies such as Denon, Creative, AQ, and ofcourse it’s own Fostex brand has a long standing reputation for making nice sounding and luxury headphones.

The  headband is soft, pleasant to the touch and has a good adjustment range of 35mm and fill fit on most heads. Clamping force is low and pretty constant over a large adjustment range. The cups can swivel in any direction and have enough ‘range’.

The pads are pleather and are slightly angled. They feel pleasant and are soft to the touch. Room for the ears is much smaller than the outer size of the pads would suggest. My ears fit fine though.

The cable is designed for home usage on hifi equipment. The cable is long and terminates in a gold plated 6.3mm TRS jack plug. It does have a luxury feel to it with that black woven cloth around it. The cable is not very pliable, a bit stiff and feels somewhat heavy but is not very microphonic. You can only hear some faint noises in the cups when the cable rubs against something.

The low impedance (22 Ω measured) makes it quite suited to be driven by portable equipment.  The impedance might be on the low side for some sources though. This headphone SHOULD have come with small connectors in the cups and a long and short lead. It is easily driven from most portable sources but does perform better on desktop amps. The efficiency is slightly higher than most headphones.

Isolation from outside noises is average to poor. Even though this is a closed headphone it still lets in outside noises. It is attenuating somewhat but even with music playing you can still hear people around you talking. Not the best if you want better isolation.

Comfort is high and the feel as well as looks is luxurious. Another important aspect of headphones is sound.
The first impression matches the luxurious feel and looks. A warm, full bodied sound with pleasant mids and ‘soft’ but quite present treble. Quite reminiscent of the Denon Dx000 series. Perhaps slightly improved though.
The bass does not bleed into the mids yet, just like the Dx000 series lacks a bit of ‘punch/impact’. It’s a bit ‘soft’ but not yet ‘wooly’ I would say ‘full bodied’ sounding. The bass integrates nicely with the rest of the sound. The voices and instruments sound ‘luxurious’ and ‘warm’ and free of distortion.
The mids could be called ‘lush’ and slightly lacks the ultimate clarity some other headphones do better.
The treble is ‘soft’ yet stays a bit behind where it concerns the finer nuances. It is a bit ‘coarse’ (not grainy or unpleasant, just lacks nuances)… sometimes.. and is a bit ‘splashy’. It doesn’t sound shrill/harsh or nasty anywhere though. Extension is great.
The stereo image is not very wide but far from small as well. Instrument placement is easy to do and ‘stable’.

On longer listening sessions the slight lack of clarity and ‘sharpish’ edge it has with some music makes me want to end the listening session sooner than I wanted. I feel a Kameleon filter is in order here to address these issues.


Type: over ear (circum-aural), closed
Usage: home
Driver type: dynamic, 1 Tesla
Pads: replaceable pleather
Collapsible: no
Headphone cup connector: fixed, dual entry
Cable entry: dual sided.
Cable: 3m terminated in 6.3mm TRS plug
Inner Pad dimensions: depth = 20mm, height = 61mm , width = 42mm (slightly angled)
Driver size: 50mm
Nom. power rating: 1.8W
Max. voltage: 6.5Vrms (19Vpp)
Max. current: 270mA
Max. S.P.L.: 126dB
Impedance: 24 Ω (measured)
Efficiency: 94dB @ 1mW
Sensitivity: 110dB @ 1V
Weight: 350 g. (without cable), 480 g. with cable
Clamping force: medium
Accessories: carrying pouch


Below the frequency response of the TH-X00 (left, Right)fr-th-x00

It measures very flat from 30Hz to 2kHz. Above 2kHz the shortcomings of this driver become ‘visible’. From 4kHz onwards the response is kind of ‘ragged’ with lots of peaks and dips close together. Extension is excellent though and goes all the way up to at least 30kHz. Most likely beyond that as well. The peak at 11kHz is probably what ‘bothers’ me the most about the treble. The ragged response usually means the treble lacks the finer nuances and may well be the case here too. Bass and mids are tonally correct though.
The bass drops off fast below 40Hz (right channel) and 30Hz for the left channel.
The lack of ‘ultimate clarity’ strangely enough isn’t very visible here. Just a narrow 5dB dip at 3kHz.

Distortion is impressively low. Most certainly in the bass (below 200Hz) where most headphones do not perform nearly this well.


The somewhat ‘soft’ bass certainly is not explained with frequency response nor with a higher amount of 2nd order distortion of bass signals.
Distortion levels are almost as low as that of the HD800 and about on par with the NightHawk. These headphones have a >45dB signal-to-distortion distance > 70Hz.

Below the CSD (left and right superimposed) Shows the driver looks well damped but somewhat ‘ragged’ in the treble. Around 2.5kHz-3kHz there seems to be some small resonance.


The spectrum plot below shows excellent behgaviour in the bass area. Much cleaner than most other headphones. The long ‘lingering’ around 2kHz is something I have not seen much. It looks like the membrane damps 2kHz stimilus pretty quickly but keeps on ringing for a relatively long time after a few ms. Don’t think it is very audible though.


Another plot is the step response. The headphone disappoints here somewhat. The steep frop-off below 40Hz is quite visble here. The sloping line whould ideally have much less ringing at the beginning and stay ‘horizontal’ for a lot longer. The weird ‘dip’ at around 4.5ms translates to 200Hz. The frequency response shows perfectly good response but the step response tells another story. 100-200Hz is where the ‘tightness’ of bass sort of resides. This ‘dip’ may well ‘explain’ the lack of ‘punch/tightness/power’ in the bass.


Below the squarewave response and needle response of the TH-X00. The 40Hz response shows bass extension is decent but not optimal. The 440Hz signal shows one of the pain points of this otherwise good sounding headphone. The tonal balance is correct but the ‘spike’ near the rising/falling edges shows the ‘peaky-ness’ in the treble pretty well.
The 100μs pulse shows there is little wrong with the speed of the this driver. Ringing is a bit longer than would have been preferred. The treble level doesn’t reach the target (green pulse level) which explains the sense of ‘slightly subdued’ treble. The small peak at the edge and the small peak after the signal shows the slight ‘edge’ to the sound.


For an easy ‘fix’ of the treble peak some toilet paper may come in handy again.

Below the frequency response of the stock TH-X00 and with 1 ply of 2-layer toilet paper in front of the driver.


As can be seen the treble peak is reduced by a good 4dB. The overall amount of treble is not reduced as much though.
The step response below shows somewhat less and shorter ringing.



  • Looks
  • comfort (pads and wearing comfort)
  • Full bodied distortion free sound
  • Non microphonic cable
  • Neutral to warmish ‘full sounding’tonal balance.
  • Soft and pleasant highs
  • Can be driven from portable sources.

Less positive:

  • Cable length and stiffness, no 3.5mm jack
  • Cable not replaceable.
  • Bass quality (lacks tightness)Treble quality, slightly lacks finest nuances and small ‘peak’.
  • Does not isolate well (for a closed headphone)
  • Needs a good seal, wearing glasses may break the seal.

This headphone does a lot of things right and shouts ‘luxurious‘ in everything.
Most people will be perfectly happy with the sound.
The less than desired tightness of the lows and the sharpish ‘treble edge’ may cause listening fatigue after a few hours and may be a deal breaker after a while for those looking for ultra detailing and tight bass. Given the price-point (as it is a massdrop colaboration) it has quite high value.
Those looking for a high-end sound will have to look further but will also have to spend a LOT more money.
Those looking for full bodied sound with a pleasant almost neutral sound need to look no further.

When measuring I found some differences between L and R. Inspection inside the cups did not show any obvious differences so I swapped the pads between Left and Right cup and sure enough the differences became smaller.
This prompted me to check how the frequency response changes when wearing glasses with thick temples compared to a good seal (taken through Kameleon).


It is obvious a good seal is quite important for these headphones. Some loss of seal means loss of bass. -5 to -10dB is quite audible. To check whether you have a good seal simply press on the cups. When the bass level remains the same the seal is good, when it increases you will know the seal is poor.

A Kameleon filter for this headphone has been made. It extends the bottom part of the frequency range and adds clarity. The treble peak is lowered and the treble is more realistic.
The treble quality, even though it is improved, still is not of a finely detailed and ‘delicate’ quality. Treble extension is great though, far above 30kHz.


Above the differences between a stock TH-X00 and via the Kameleon (left channel only)
Some smoothing is applied which show how average levels have changed.
The bass extension is obvious. The increase in clarity does not seem that much (about +2.5dB) but is clearly audible. The treble peak is lowered and extension above 20kHz is also obvious.

Below the CSD through the Kameleon. The peak at 10kHz is much lower.


The distortion is still impressive, certainly in the area below 200Hz. Clean and tight bass response.


The step response has greatly improved as well…..


Below the frequency response of both channels (left, right) in one plot. The difference between left and right is something in the headphone could be the driver or the pads.

Via the Kameleon the bass is ‘tighter’, the clarity has improved and the treble is more realistic, less ‘soft’ but also less ‘peaky’.
Those that prefer the mellow, warmish sound signature and like the laid back ‘soft’ treble may not be charmed by the changed sound signature.
Those that find the stock sound to ‘mellow/mushy/romantic’ and want a bit more ‘bite’ will probably like the sound via the Kameleon.

Variable smoothing has applied to the plots below. This shows the perceived amount of treble a bit better than the not-smoothed plot above.


Quite enjoyable and full sounding comfortable headphone now.

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