T1 (mk2)
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published: Jul-16-2017
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.
The 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.
Beyerdynamic T1 (mk2)
The Beyerdynamic T1 (2nd generation) is a semi-open over-ear (circumaural) headphone with a Tesla-driver. Semi open means it does leak some sound and lets some ambient sounds in but attenuated compared to fully open designs.
This headphone is definitely not intended for portable usage as the impedance is a far too high (600Ω) to be driven from phones/tablets and small DAP’s. It is intended for home and studio usage.
With an MSRP of around € 1200.- it is quite expensive. It is Beyerdynamics ‘flagship’ headphone. It is in the same price range as the Sennheiser HD800.
The pads on this model are velours and replaceable.
As usual also this Beyerdynamic headphone is very comfortable.
specifications:
Type: Over ear, semi-open
Usage: Home, studio
Driver type: dynamic (Tesla)
Pads: replaceable velours with memory foam
Foldable: No
Headphone connector: locking 3,5mm TRS (color coded for L and R)
Cable entry: double sided
Cable: 3m with gold plated 3.5 mm TRS plug and 6.3 mm adapter
but also available is a 1.4mm balanced TRRS to 2x TRS cable and a 3m cable to 4-pin XLR for balanced operation.
Driver size: 45 mm, angled
Nom. power rating: 0.3 W
Max. S.P.L. 126 dB (20Vrms)
Impedance: 600 Ω
Efficiency: 102 dB @ 1mW (500Hz)
Sensitivity: 104dB @ 1V
Weight: 360 g.
Clamping force: medium
Accessories: hard storage box
measurements:
Below the frequency response of the T1 (mk2) (Left, Right)
The T1 has slightly rolled-off bass extension. The tonal balance is ‘warm’. The ‘dip’ between 2 and 4kHz is less ‘deep’ in reality as the plots suggest. This is due to the angled drivers and their placement. Because of this driver angle the concha-gain of the pinna compensates this a bit by boosting frequencies in that frequency band a little. As this test rig does not have a pinna the dip thus measured slightly more recessed compared to how it sounds. Compared to ‘neutral’ headphones this headphone has a ‘laid-back’ sound and is lacking in clarity/presence. The treble is quite elevated but not of poor quality in itself and sounds highly (overly ?) detailed. A bit like the HD800.
Below the HD800 compared to the T1.
To make the tonal balance difference a little clearer below the same plot as above except the traces are 1/3 octave smoothed. HD800 vs T1
It is obvious there are quite a few common traits such as slightly rolled-off sub-lows and elevated treble without deep dips and peaks.
Still the T1 is somewhat bassier and a bit more laid-back. The treble peak at 6kHz annoys quite a few people (that’s why the HD800S exists) and the T1 does not have that. Both headphones have boosted treble above 8kHz which is responsible for the ‘highly (overly ?) detailed sound. Because the elevated treble response part only has small peaks and dips the treble quality is high.
There is also a portable version in the same price class in the Beyerdynamic stable. This is the T5P (P stands for Portable). This, of course, is a closed headphone.
Below the tonal balance difference between the T1 and T5P (both 2nd generation)
The T5P has somewhat more bass and is less ‘warm’ in the mids. Slightly elevated bass is a good thing in portable headphones. The fact that the 150Hz portion only has a narrow boost can make the ‘accuracy’ of bass instruments sound a bit ‘off’. The treble part is less boosted. This makes the T5P slightly less ‘edgy’ and a bit more ‘subdued’ yet still detailed enough because of the boosted 9kHz band.
A ‘cheaper’ high quality Beyer headphone that is tonally close to the T1 is the Amiron.
The Amiron is about half the price of the T1 so is a lower cost alternative.
The T1 has more treble extension so will sound a bit more ‘airy’. This makes the T1 more ‘refined’. The Amiron has a few dB more sub-bass but overall these headphones are more similar sounding than not.
Below the distortion measurements of the T1 (Right channel).
Note that this headphone was measured at 
where background noises were present in the demo room. As this is a semi-open headphone the distortion levels and spectrum plot performance may thus be somewhat better in reality than as shown on the plots due to ambient sounds being measured along with the headphone.
The 2nd harmonic distortion level (below 1%) in the bass is very low. The distortion around 8kHz is only 0.3%. These distortion numbers are excellent.
Below the distortion plot but displayed in percentages.
Below the CSD of the T1. (Left and Right are superimposed)
The mids seem quite well damped. In the treble there are some short lived resonances are visible but no long ones that can be sound degrading.
output resistance / damping-factor
As this is a high impedance dynamic headphone the frequency response might only be slightly amplifier output resistance dependent when certain higher output resistance amplifiers are used. In the high-end desktop amp world chances are higher that you can encounter a high output resistance amplifier.
To test this the headphone is measured via a low impedance amplifier (0.2Ω) and a high impedance amplifier (120Ω). On a higher output resistance amplifier the output level will be slightly lower. To compensate for this the amplifier is cranked up a bit to the same level (at 1kHz) as the low impedance amplifier. This way the plots are overlay-ed and it is easy to see how the tonal balance changes.
There is ‘only’ a <1dB boost in the lows. (Right channel is measured). This is not really audible so very safe to connect it to all kinds of desktop amps and even directly to the speaker output of power amps (max 100W)
The CSD below shows the mids also aren’t affected much by the higher output resistance. The driver remains well behaved in the mids. From (0.2Ω) and (120Ω) amplifier .
Below the spectrum plot of the T1 which doesn’t show any alarming issues.
The spurious signals in the upper middle part of the plot are ambient sounds and not from the headphone itself. At 8kHz the peak is visible.
The step response (Right channel) below shows the bass is a bit rolled-off. There is quite some overshoot and some reasonably fast damped resonances. 
summary
The Beyerdynamic T1 (2nd generation) is the Beyerdynamic flagship. It must compete with the HD800. It is different in tonal balance. Both have elevated treble but the Beyer treble is slightly less ‘aggressive’. The sound is pleasant/warmish and highly (overly ?) detailed.
When you aren’t bothered by the typical (Beyer) treble peak. 1 or 2 plies of toilet paper in front of the driver can help somewhat or a passive filter to reduce this issue then the T1 mk2 does a lot right when you prefer a laid-back sound.
Overall a quite expensive but nicely made closed headphone. Those not willing to fork out that kind of money can have a look at the Amiron for half the price of the T1 and only sacrifice the treble slightly (and the looks)
DIY-Audio-Heaven 