Sennheiser HD424 Headphones today . . .

Discussion in 'Headphones' started by tubeboob, May 14, 2011.

  1. pmsummer

    pmsummer simul justus et peccator

    Been listening to my HD-424 'phones since 1973. Just installed my third pair of cushions.

    BTW: B&H Photo sells the pads for $6 a pair. Because they are sealed in airtight bags, I just bought two extra pair and stored them in a cool dark place. Probably a lifetime supply.
     
  2. acacia

    acacia New Member

    Messages:
    4
    I still use the HD 424. I have looked in vain for a review / comparison between them and Sennheiser's latest offerings without success.

    So, I wonder how they compare against, say, the HD 800 ?
     
  3. enginedr

    enginedr Well-Known Member

    Messages:
    657
    Location:
    nyc
    I brought my 424s with me to last years NY audio show to compare them with other phones in the $ 500.00 range . After that I decided to stick to my trusty 424s I had
    Since 1978 . One thing I can say is they are very comfortable . If I want better I have
    To spend in the $ 800.00 range
     
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  4. halnwheels

    halnwheels New Member

    Messages:
    4
    I'm also an original owner of the 424, and on my third set of ear pads. My last set seemed to dissolve rather prematurely. I play through my various vintage equipment when I need to avoid disturbing my family. I've got no reason to replace them.
     
  5. MFGuy

    MFGuy New Member

    Messages:
    18
    You've inspired me to refoam my 424's.
     
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  6. MFGuy

    MFGuy New Member

    Messages:
    18
    Got the foams today and I'm in heaven. Why can't they make foams that last? Sennheiser, are you listening???
     
  7. pmsummer

    pmsummer simul justus et peccator

    Germans like real rubber, as opposed to synthetics. Just ask any BMW, Porsche, Mercedes owner (throw in Audi, VW and MINI).

    Real rubber seems to be more acoustically transparent (critical to 'on-ear' designs and speaker facias). Life-span becomes secondary to fidelity.
     
  8. MFGuy

    MFGuy New Member

    Messages:
    18
    Real rubber...interesting. Thanks for the info. Always owned VW's and my Alfa has a wood steering wheel. Does that count?
     
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  9. pmsummer

    pmsummer simul justus et peccator

    Ever have to replace your door gaskets on VW? ;-)
     
  10. Pauln

    Pauln Active Member

    Messages:
    481
    Location:
    Houston
    The file has measurement graphs for the HD-424...
    - frequency response
    - impedance and phase vs frequency
    - %THD+noise @ 90dB and 100dB
    - impulse response
    - isolation of external sound vs frequency
    - 30Hz square wave
    - 300Hz square wave

    Impedance matching is only important when power is being transferred. The high impedance means only a very small power is needed - for 90dB it's only 0.08mW which is 0.00008 watts or one twelve and a half thousandths of a watt (1/12500 of a watt). In practice it is even less because amps and receivers back then typically had a resistor pair of a few hundred ohms going to the headphone outputs as well. With the high impedance of the HD-424 they may be connected directly to the speaker outputs on the amp.

    In fact if you have monoblocks you can cut the headphone cable at the plug (or order a new cable to experiment) where you will find that the twin pairs of wires from the phones become three wires (the grounds are connected) to make the three conductor connection to a headphone jack (tip-ring-sleeve TRS). Once you have the four wires, these pairs may be connected to the individual channels whereby since the two chassis are separate they don't share a common signal ground. The four wires are small, so the best way is to use a terminal strip like in a crossover so you can pass a little bigger and more manageable wires to the amps' outputs.

    The sound quality of losing the common signal ground in headphones is worth the effort.

    Oh yeah, I got mine in the mid 70s and they are still the only ones I've ever owned, still love them, great phones.
     

    Attached Files:

  11. cgutz

    cgutz AK Member

    Messages:
    3,244
    Location:
    SE South Dakota
    I read in manual you can connect HD424 headphones straight to speaker outputs. Thought about building an adapter with a female 1/4 plug but never been courageous enough to try.

    If I went this route I could plug them into my vintage Bell Tube amp speaker connectors, but with no other speakers would it harm the amp? With an impedance of 2k ohms on the headphones, would I use 4, 8 or 16 ohm speaker outputs on the amplifier?
     
  12. Pauln

    Pauln Active Member

    Messages:
    481
    Location:
    Houston
    I think with high impedance headphones, especially 2000 ohms like the HD-424, what they need is sufficient voltage with little requirement for current or power. An amp rated for only 1 watt into 8 ohms would be doing so with 2.83 volts, so all power amps are plenty sufficient. Tube amps will provide plenty of voltage since the phones will play loud with 0.5V and very loud with 1V.

    Usually, the two things of concern are damping and impedance interaction. Damping is derives from the relationship of the amp's output impedance to load impedance, and generally one wants the load impedance to be 8 or 10 times the amps output impedance. Impedance interaction is how the load's varying impedance with frequency causes the delivered power to vary with frequency, resulting in an inaccurate frequency response.

    Both the above issues are a concern for low impedance phones; high impedance phones makes both issues negligible.

    On the choice of taps on the output transformer... I think with 2000 ohm phones all the calculations are going to pretty much approach the same values, so you might try all of them and see if you can hear a preference. When using normal low impedance regular speakers (where power is being transferred) I think one would expect the output transformer to generate more heat with the 4 ohm tap and less with the 16 ohm tap. I don't know, but with the phones I suspect all the taps will present a cool transformer.
     

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