HD250 Linear MK1

Discussion in 'Headphone Measurements' started by ultrabike, Apr 26, 2016.

  1. ultrabike

    ultrabike Measurbator - Admin

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    @Cspirou visited and brought with him this collector item. These are not the somewhat easier to find HD250 Linear II but the original Linear MK1 from Sennheiser. These seem indeed a bit hard to find, and I think @Cspirou got a great deal out of them.

    [​IMG]

    These seem to be from the early 80s, and this goes to show that durability was not crap then. The pads are replaceable. The impedance I was told was in the 600 ohm range (didn't check) and the headphone cable seems custom and designed to be connected in parallel with other similar headphones. This may explain the need for high impedance. The sensitivity is also quite high as I was able to drive them to 90 dB with my 2i2 w/o going past 12 o'clock even with such a high impedance.

    They are a bit shallow in the cups and discomfort may arise if ones ears touches the insides of the cup. Pressure is not an issue, but these are rather old cans. Even so, seal was not too hard to attain.

    The sound it's rather balanced and isolates decently. These seem to be monitor closed headphones and they sound like such. I felt they were a bit edgy with some songs, but not too much. They are also somewhat warm and pleasant. However, they really shine with certain kinds of songs. Specifically, @Cspirou pointed me to some of his favorite tunes, and I felt these cans sounded fantastic with such material.

    Here are some further impressions from his majesty's site:

    http://www.head-fi.org/t/603099/sen...2-hd450-hd480-ii-hd480-classic-and-surrounder

    Anywho, here are some measurements:

    Frequency Response

    HD250Linear_fr.png

    Distortion Right

    HD250Linear_Dist_right.png

    Distortion Left

    HD250Linear_Dist_left.png

    CSD Right

    HD250Linear_CSD_right.png

    CSD Left

    HD250Linear_CSD_left.png
     
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  2. Armaegis

    Armaegis Friend

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    Early studio headphone distribution amps were literally just a simple power amp with a whole bunch of jacks wired up in parallel off the output. A high power high temperature trim pot would be placed in front of each jack to control output. A high impedance headphone would be required in order to limit how much current was getting passed through the pot and to debatably get a more linear response from the pot depending how it was wired up.

    Of course, in situations where headphones are being daisy chained in parallel without individual pots on each, then yes you want a very high impedance on each headphone so that the resultant load isn't too low for the amp.

    600 is a nice big number, and also a holdover from the old radio transmission standards (pretty sure tube amps were part of the equation too since that's the era it was developed).
     
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  3. Cspirou

    Cspirou They call me Sparky

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    Thanks for letting me watch! It was a really educational experience to see how the measurement process works and I'm glad to finally see how these measure.
     
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  4. Cspirou

    Cspirou They call me Sparky

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    Well there goes this pair. The right driver gave out. :( Not likely to find a replacement since these were discontinued in 1992. Good thing I bought these used for cheap.
     
    Last edited: Aug 29, 2016
  5. ultrabike

    ultrabike Measurbator - Admin

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    Sorry to hear that @Cspirou. Is it something you can fix, like a loose wire or something like that?
     
  6. Cspirou

    Cspirou They call me Sparky

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    I'll need to investigate, hopefully it's a wire I can reconnect.
     
  7. Armaegis

    Armaegis Friend

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  8. Cspirou

    Cspirou They call me Sparky

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    These are still the best closed headphones I've tried so far. Not the most comfortable, but the pleather pads the seller is including might help with that.
     
  9. Biodegraded

    Biodegraded Friend

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    Sold :D

    After some listening, will think about modding along the lines of @stratocaster 's tweaks to the mk2 (which is what got me interested in these in the first place).
     
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  10. Biodegraded

    Biodegraded Friend

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    Yep, no shortage of ohms:

    [​IMG]

    The plug is Sennheiser's PX1 stackable-DIN thing, as in Fig 2 here (PDF). The cable is obviously original and has gotten really stuff and unwieldy, but luckily 6x0 2-pin plugs fit in the cup ends, and having a 2m HD6XX cable spare I've substituted that.

    Only had a quick listen so far, but I think they have possibilities. Bright in the treble, so will have a go at some front filtering; but the replacement pleather pads (Brainwavz, I think) put on by the previous owner seem to have eliminated the 200 Hz dip.

    Measurements are pretty rough. The bass roll-off is more a function of my 'head' geometry than reality, I'll need to play around with it a bit more to get it satisfactory. Ref at 80 dB because otherwise those treble peaks will clip in my system, and the poor little Nano BL didn't have a lot of room left...

    [​IMG]
     
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  11. Cspirou

    Cspirou They call me Sparky

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    Oh these need some voltage for sure. I find myself near max on weaker amps
     
  12. Biodegraded

    Biodegraded Friend

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    Heh - yeah. Listening was on Magni (where these will live) on high gain. Nano is for listening from the computer and for measuring.

    Did you manage to fix your pair?
     
  13. Cspirou

    Cspirou They call me Sparky

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    Nope, i have one functional driver. I opened up the other one and it requires some surgery that I'm not skilled enough to do.
     

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