HD250 Linear II

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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.
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.

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Sennheiser HD250 Linear II

HD250 Linear II

The Sennheiser HD250 Linear II is a closed over-ear dynamic headphone. It is a quite old headphone (from around 2001) already but when you can find one second hand for not too much you will own a closed ‘fun’ headphone that sounds surprisingly ‘open’ with DEEP bass and feisty treble. Isolation is quite good.
The headphone is comfortable and lightweight with a low clamping force. The pleather pads may become somewhat ‘sweaty’ on longer listening sessions.
The cable can be changed. The cable is quite long and somewhat microphonic.

specifications:

Type: Over ear, closed
Usage: Home
Driver type: dynamic
Pads: replaceable pleather
Foldable: No
Headphone cup connector: 2 pin Sennheiser connector
Cable entry: dual sided
Cable: 3m 3.5mm TRS to 2x Sennheiser plug
Driver size: 38mm
Max power rating: 0.2W
Max. S.P.L.: 120dB
Impedance: 300 Ω
Efficiency: 96dB/1mW
Weight: 215g. cable ads 60 gr.
Clamping force: low
Accessories: 6.3mm TRS adapter

Sound description:

Big bass… Not perse the type of bass what bassheads are looking for though. It goes deep but is not ‘detailed’ as far as bass can be that. The bass is somewhat dis-attached from the mids. I prefer that over bloated bass myself. The mids are realistic and clear. Even though the bass and treble are considerably boosted the mids don’t sound recessed at all.
Open, forward with good clarity/presence.
Then there is the treble. When you are coming from Grado or Beyerdynamic headphones the you may not find the treble objectionable. When you are used to more neutral headphones the treble can be harsh and grating with a lot of recordings. It does give the impression of being extremely detailed because of it. But … it’s just boosted upper treble.
Not really suited for portable usage unless you have an amplifier or only want to play music softly.

Measurements:

Below the frequency response of the HD250-II (Left, Right)

FR HD250-II

This tells the story indeed and shows perfectly what is heard. Big bass (+10dB). The small dip around 200Hz ‘disconnects’ the bass from the mids. Those mids are very realistic and as ‘neutral’ as can be. From 300Hz to 2kHz it is impressively flat. The treble area is about +10dB opposite the mids. This is quite a lot and very audible. At around 11kHz +15dB is reached !

 

output resistance / damping-factor

As this is a dynamic headphone the frequency response might be amplifier output resistance dependent when certain higher output resistance amplifiers are used.
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 considerably lower. To compensate for this the amplifier is cranked up 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.
FR HD250-II R 120

The tonal balance changes just slightly when connected to a higher output resistance amplifier. You get about 0.5dB more bass. This will not be audible so it is no problem to drive this headphone from amplifiers with a higher output resistance.

Below the distortion plots of the HD250-II.
The distortion products are shown in dB. Below the left channel is shown.Dist HD250-II L

 

The distortion profile is quite typical for a dynamic driver. Higher 2nd harmonic distortion in the bass. Below the right channel.

Dist HD250-II R

When one looks closer the Right channel has a lot less distortion around 200Hz.
To show this a little more clearly below the same distortion plots but in percentages instead of dB distance. Left channel below.
Dist HD250-II L percent
Those levels are VERY high. 7% at around 200Hz is quite severe and is possibly the reason why the bass isn’t exactly ‘detailed’ and only ‘booming loudly’. Below the right channel.

Dist HD250-II R percent
Bass distortion is MUCH lower here and are normal levels. 2% 3rd harmonic for the lowest frequencies is not so bad.  1% for the 2nd harmonics is ‘normal. The mids  are quite good with levels between 0.1% and 0.2%. Clean mids …
It looks as though the left driver may have some issues. I would expect most HD250-II’s to perform close to the Right channel of this one.

Below the CSD of the HD250-II (Left and Right channel are superimposed)
CSD HD250-II

Some ringing is visible at 8kHz and 11kHz as well as 17kHz. Even at about 27kHz it rings.
I would not be concerned about that one though… The slight wiggle at 3kHz is not audible. Mids appear to be reasonably well damped.

Below the spectrum plot of the HD250-II (Left channel)spect HD250-II L

Some small lingering around 2kHz and 3kHz but these are not sound threatening. Otherwise this looks pretty decent. Bass does linger on a bit longer than desirable and may also be responsible for the somewhat ‘fatty’ bass.

Below a step response plot of the HD250-II (Right channel)
step HD250-II R

The step response clearly shows the ringing. This ringing is poorly damped and simply is too high in amplitude and rings on way too long. The bassy character is shown by the somewhat lower initial rise of the signal and the +5dB hump afterwards. Below the left channel.
step HD250-II L

The left channel seems slightly better damped.

Below the square-wave and impulse response plots. On the left the Left channel, on the right the Right channel.
SQR
The difference in the bass (40Hz square-wave) is quite visible here. The left and right plot don’t look quite the same.
The 400Hz square-wave shows the considerable ringing. This is also visible in the impulse response plots. There is overshoot and the impulse has lost it’s shape and has turned into lots of ringing instead.

summary

This headphone is great for those that like impressive (thunderous) bass and like heavily over-accentuated cymbals and isn’t afraid of feisty treble. The mids and overall sound is excellent. So is the comfort. When you can find one of these 2nd hand and don’t have to pay absurd prices. Between € 50.- and €125.- is probably a fair price depending on the condition of the pads. Original pads may be hard to find. Perhaps on e-bay one can find replacements. The ring would have to be re-used in that case.
The headphone is quite comfortable.
Quite suited for home usage and when driven from an amplifier that can supply a reasonable voltage.

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