Earphones puzzle

Discussion in 'Pro Audio' started by synergo, Oct 3, 2008.

  1. synergo

    synergo Guest

    Can anybody explain the following?
    I switched from Samplitude to Sonar. So, I am following the usual
    routine and recording some chamber music for piano and cello - exactly
    with the same setup that worked perfectly before. But this time I hear
    lots of glitches: some are clicks, some are crackling, or I would
    rather call it some sort of sizzling. Most of them fall on the peaks -
    relative peaks - the level is about -20 dB. I playback it for few
    times - the position of the artifacts retains the same in every
    playback. So, artifacts are indeed recorded. To verify, I import the
    soundtrack from CD. No glitching. So, it's a recording problem.
    For few hours I played around with buffering and WDM vs. ASIO. No any
    advance.
    I was listening through the earphones - Sennheiser HD600. Then I
    decided to switch to the speakers - surprise: glitches were gone!
    Intrigued, I changed the cans to Sony MDR 7506. No glitches at all!
    I exported the recorded track to wav. and played it in Wavelab. The
    same: HD600 glitched, MDR 7506 did not. Then I brought the master
    slider in Wavelab 7 dB down - HD600 stopped glitching. Anything above
    -7 dB, and few isolated clicks appear.
    I checked on few different headphone preamps - the same result!
    What I do not understand: if HD600 has quite higher impedance than MDR
    7506, then why the softer level agrees with it better? Sonically it
    appears as though HD600 distorts because of the overload, but where
    can this overload come from? The preamp is all in green area. The
    software shows the highest peak as -16 dB. The hardware mixer is at
    unity - nothing even close to "yellow".
    I am totally lost. I googled the HD600 on the subject of deterioration
    or failure, but it appears that both, the brand and the model enjoy
    quite good reputation. No complaints at all. I asked a buddy to bring
    his HD600 on Sunday - to compare the output. But so far, what could be
    at fault?
    Alex
     
    synergo, Oct 3, 2008
    #1
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  2. synergo

    synergo Guest

    A/D is on the sound card [Delta 1010] - locked to internal sync in the
    Delta driver.
    Sonar is set to Trigger & Freewheel Sync. The only other option is
    Full Chase Lock, recommended for chasing to MTC.

    Pardon. HD 600 sounds at least twice softer than MDR 7506 on exactly
    the same playback settings.
    HD 600 - 200 mw 300 ohm
    MDR 7506 - 1000 mw 24 ohm
    No no no. It is much much softer throughout all the levels of
    playback.

    This, combined with the fatter bass of the Sony (which would tend
    I can swear there is no distortion on Sony at all! Crackling is
    broadband. And the amount of it I hear on Sennheiser cannot be likely
    masked by any EQ.
    Zooming into the wave in the Wavelab does not show any anomalies.
    It indeed appears that some component in the chain becomes overloaded.
    But which?
    The most likely candidate is the HD600. But if it gone sour, the
    playback at low listening level remains very balanced and clean.

    Alex
     
    synergo, Oct 3, 2008
    #2
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  3. I have both the HD600 and the 7506 and at a given "volume level" my 7506
    plays a lot louder.

    This is with my Mackie 1604VLZ, BigKnob or even my iPods.

    If I remember my EE maximum power transfer occurs when the load matches the
    output impedance the driver is looking for. Use anything else and the
    output will change either in terms of level or distortion.

    What are you plugging the phones into?



    --
    Moshe Goldfarb
    Collector of soaps from around the globe.
    Please visit The Hall of Linux Idiots:
    http://linuxidiots.blogspot.com/
    Please Visit www.linsux.org
     
    Moshe Goldfarb., Oct 4, 2008
    #3
  4. Correct :)
    Distortion is another animal though.
    At least going high impedance to low impedance, which is NOT the case here.

    I go back to when they taught tubes in EE and back then load was real
    important.
    Bridging and all that kind of crap.

    Bottom line though, on my systems the HD600 are not as loud as the 7506 at
    a given *volume level*.

    What is he connecting these things to?
     
    Moshe Goldfarb., Oct 4, 2008
    #4
  5. Sennheiser says that their HD600's "characteristic SPL" (presumably
    meaning dbSPL at 1mW, the old classic "standard") is rated as "97dB".
    No other description in their .pdf (shameful, but there it is).

    The Sony MDR 7506 is typically listed as "106dB/W/m", which
    might (very generously) be (RE)interpreted as 106dbSPL at 1mW,
    because the literal interpretation is impossible (equally
    shameful, but that's life).

    The Sennheisers are nominally 300 Ohms and the Sonys are nominally
    63 Ohms. IOW, these models have very similar "power" sensitivities
    and 9dB different voltage sensitivities.

    In the professional world, delivering powers enough to cause
    hearing damage is pretty much expected (if seldom used!). But
    modern "consumer" electronics could possibly have cut enough
    corners in the headphone output to have allowed voltage
    clipping to the Sennheisers. Lame, but possible.

    And, as many others have already said, you haven't described
    the actual electronics involved. Of course; noboby ever does.

    All the best fortune,
    Chris Hornbeck
     
    Chris Hornbeck, Oct 4, 2008
    #5
  6. synergo

    Mike Rivers Guest

    Your problem can probably be explained by Ohm's Law. Since the
    impedance of the Sennheiser headphones is much higher than that of the
    Sony, while they may take about the same power level to achieve the
    same listening volume, the Sennheiser, requires higher voltage (and
    less current) than the Sony. The amplifier that's driving the
    headphones may not be capable of providing sufficient voltage to drive
    the Sennheiser phones at the volume you desire.

    Another possibility, if you're using a volume control in your computer
    to turn up the listening volume, you may be overdriving your sound
    card.

    It's also possible that the Sennheiser headphones are damaged, since
    you mentioned that you tried several headphone amplifiers and got
    similar results with any of them. Do you have a stereo receiver with a
    headphone jack that you could test them with.

    If they crackle when driven by a standard "living room" stereo
    amplifier, they're fried. If they don't, try feeding that amplifier
    with the output of your sound card, boosting the volume with the
    receiver's volume control if necessary.
     
    Mike Rivers, Oct 4, 2008
    #6
  7. Has he tried them in another piece of equipment?
    What is he plugging them in to? (I must have missed it).
     
    Moshe Goldfarb., Oct 4, 2008
    #7
  8. synergo

    Paul Stamler Guest

    Only if you're lowering the impedance *from a matched* impedance.
    Except that it almost never happens. Tubed power amplifiers typically have a
    "damping factor" of about 20, meaning that into an 8 ohm load they have an
    output impedance of about 0.4 ohms. (I'll ignore the fashionable
    single-ended triode amps with zero feedback. They're a story unto
    themselves, and not a pretty one for hi-fi.)
    Neither is McIntosh. See above.
    An amplifier can be thought of as a perfect voltage source (zero output
    impedance; doesn't change its output regardless of what load you hang on it)
    in series with a resistor (in the simplest case; I'll ignore reactive stuff
    for now). That's the output impedance.

    Let's say you have an amp with an output impedance of 1 ohm, and the perfect
    voltage source inside it is putting out 10V. (In what follows, something
    like "6.6bar" means "6.6 with a bar drawn over the post-decimal-point six to
    indicate that it repeats forever".)

    Hang a 10 ohm load on it. The voltage source will then be dropping through
    11 ohms (1 ohm internal, 10 ohms in the load), so it will draw 10/11 =
    0.909A. Power delivered to the load is (i squared) times R, or 8.26W.

    Now hang a 5 ohm load on it. The voltage source will now be dropping through
    6 ohms, so will draw 1.6barA. Power delivered to the load is now 13.8barW.
    So the guy who said power increases as you drop the load impedance was
    right -- so far.

    Hang a 1 ohm load on the amplifier. The voltage source will now be dropping
    through 2 ohms, so will draw 5A. Power delivered to the load is 25W.

    Finally, hang an 0.5 ohm load on the amplifier. Now the voltage source is
    operating into a 1.5 ohm load (1 ohm internal, 0.5 ohms external), so draws
    6.6barA. Square that, multiply by 2, and you get 22.2barW -- less than you
    got into 1 ohm, which was the matched impedance. So you're right too --
    maximum power's delivered when the source and load impedances are matched.
    Of course, before this happened the current limiters in the amp have gone
    into protection mode, or the amp has burned up.

    In practice, with modern power amplifiers, impedances are not matched; the
    output impedance is always less than the load impedance, so the delivered
    power goes up as you drop load impedance. But if you could get down to
    matched impedances and below, you'd find the delivered power dropping off
    again. In the real world, nobody does that, so you don't see it.

    Peace,
    Paul
     
    Paul Stamler, Oct 4, 2008
    #8
  9. synergo

    synergo Guest

    That could explain why overall volume of HD600 appears softer. But why
    do I get clicks on HD600 whereas their overall level is still way
    lower than Sony? Just 5 minutes turn up (on the rotatory button of the
    mixer) increases the amount of clicks. 10 minutes brings in crackles -
    very typical of overloading distortion - yet all of it with the level
    of the mixer not even reaching yellow, so is the software.
    The only chance for overdrive is the Delta driver (before it reaches
    the software program). In the Delta control panel I see that the
    spikes coming quite close to the top. It is possible that there are
    some short transients momentarily hitting over, not reflected by the
    crude meter.
    Bringing the volume down makes the sound unacceptably low in loudness,
    but quite balanced, free of any artifacts.
    I tried the headphone amp in Mackie CR1604 VLZ. It is quoted as 120
    ohm; in Spirit Folio FX8 - 75 ohm and Rolls little box - no specs.

    However, today, on Sunday evening, I got some time to play around -
    and discovered what appears to be a culprit. I wonder, if anybody can
    explain that: the problem went away when I switched the 1/4 to 1/8
    stereo golden adapter from unknown manufacturer to the RadioShack one.
    I started trying all the adapters I could find (5), and 3 of them
    brought very noticeable sonic differences. I suspected that they could
    have turned defective (although God knows how can you ruin a solid
    piece of metal), and tried them on the MDR 7506, and guess what! 2 of
    the ones that made HD600 deteriorate did not make any impact on MDR
    7506, and vice a versa, 1 that sounded great on HD600, caused
    noticeable flatenning of stereo image and loss of low end on the MDR
    7506! Is it woodoo?

    All adapters are clean and snap well. 3 out of 5 are threaded.

    By the way, with the best sounding adapters chosen for each of the
    cans, Sony did pick much more detail in the mid low range of recorded
    stereo image, which made imperfect material sound more imperfect.
    Whereas Sennheiser some sort of flattered all recorded material by
    making the overall image sort of blend in. I still could eventually
    find the same faults I discovered with the Sony, but with twice more
    listenings. This experience was quite opposite to my earlier
    observations while mastering some orchestral classical recordings.
    There Sennheiser used to reveal more subtle differences between
    various parameters of the plugins. Of course, God knows which adapter
    happened to be there on HD600 at that time!

    However, this makes me guess if headphone manufacturers also design
    their produce according to particular application - say, editing
    versus recording - similar to the speaker manufacturers.

    Alex
     
    synergo, Oct 6, 2008
    #9
  10. Of course it is. When the output resistance of the amp is very low, both
    phones get the same voltage. But the one with the highest impedance draws
    the least current and thus the least power. So a low impedance headphone
    will per definition sound louder than a high impedance one.

    Maybe the headphone amp has a defect which shows when the load is low and
    possibly the output voltage is high. Try to connect the senny and the sony
    in parallel and check whether the distortion in the senny is still there. If
    not, your headphone amp is toast.

    Meindert
     
    Meindert Sprang, Oct 6, 2008
    #10
  11. synergo

    Mike Rivers Guest

    I think we're beyond trying ot troubleshoot this with text. I really
    can't relate your "amount of clicks" with what's actually happening
    electrically without hearing it and perhaps looking at what's actually
    getting to the headphones, using an oscilloscope. We have a vocabulary
    issue here, and I really don't know what you're doing .

    I still suspect that it's voltage-related, however, unless it's simply
    a connector making poor contact..
    Sorry, but you've lost me. What mixer, what button, what meter? Here's
    how I see it:

    The volume level in the phones is too low so you turn up a volume
    control somewhere.. This causes the voltage applied to the phones to
    increase and makes them a little louder. The voltage can only go so
    high, however, since it's limited by what the power supply can put
    out, and that's still not enough voltage to drive the headphones to
    the volume that you desire. The voltage over a cycle rises to the
    maximum it can, and then the top of the waveform flattens out, making
    a two sharp corners at the voltage peak (one going up and the other
    coming down). That flattened out waveform can sound like clicking or
    crackling until the flattened portion becomes too wide. Then it
    becomes what nearly everyone describes as distortion. But I really
    can't tell if this is what's happing with your system because I can
    neither see nor hear it.
    Meters rarely tell the whole story. If you're pushing levels anywhere
    near the peak of any meter, you're likely to have problems somewhere.
    That's consistent with what I've been telling you, but there are
    several places in the signal chain where you could "bring the volume
    down" and you may not have found the right one yet. If you send a
    distorted signal to whatever amplifier is driving the headphones, it
    will be distorted in the headphones at any volume. If it's not
    distorted going in to the headphone amplifier but it's distorted
    coming out, then the problem is with the headphone amplifier or the
    headphones, or how you have the amplifier's controls set.
    You had a dirty or loose connection. Instead of acting like an
    electrical conductor, it was acting like a SEMIconductor and clipping
    off the peak of the voltage waveform. The reason why clipping occurred
    at different volume levels with the different headphones (trust me -
    the ones that appeared to work were being clipped, too, just at too
    low a level for you to hear) was because the higher impedance ones
    required a higher voltage to reach the volume you desire, and the
    clipping from the diode formed by a bad electrical connection has a
    VOLTAGE threshold.

    Get some contact cleaner and spray the plugs, jacks, and adapters. A
    secondary thing is that not all of these adapters, jacks, and plugs
    are all that precisely made. If one is just a little too loose in the
    wrong place, it can cause this sort of trouble. We see it in studio
    patchbays often. I keep a can of DeOxit contact cleaner handy in my
    studio and it fixes a lot of problems.
    I was just talking to someone at the AES show yesterday about that
    issue. This was a company that makes assembled cables, and they found
    that the plugs that they were getting from a particular supplier had
    some that were enough undersized that they didn't make solid contact
    with some jacks from other manufacturers.

    I guess that's still not a good enough test to assure that they're
    working correctly.
     
    Mike Rivers, Oct 6, 2008
    #11
  12. synergo

    John Connors Guest

    I think you've hit the spike on the head Mike !

    I keep the Caig Labs survival kit handy in my studio for solving these
    types of problems.

    Also, the Sony 1/4 inch to 1/8 is a screw on type and I have found that I
    get mixed results any time I use a regular non screw type adapter.
    Some seat well and others do not.

    Additionally, it goes without saying that anytime one is dealing with 1/8
    mini plugs anything can and will happen due to the contact surface area
    etc.

    I'm not one for hearing differences in cables as long as they are all well
    made and that some weird combination of reactive or capacitive component
    isn't going on.
    However, I have heard differences when one cable is having connection
    problems, even very minor ones and it can be a bear to hunt down.
    As we all know!
     
    John Connors, Oct 6, 2008
    #12
  13. synergo

    synergo Guest

    Normally, from the +4 dBu of the Delta card into Mackie 1604 VLZ Aux
    inputs, about 11 o-clock gain, C/R Phones at 12 o'clock, and Main mix
    at unity.
    Yes.

    The problem definitely goes away when the adapter is changed for a
    better one.

    Well, to sum up, it pays to have the stock of adapters at hands, and
    from time to time run comparison tests - at least before starting an
    important project. Earphones are way too precious source of finetuning
    the finicky plugins during mastering or restoration - more useful than
    speakers then - perhaps it is worth of investing some extra into the
    array of fancy cables and good earphone amp.

    Alex
     
    synergo, Oct 7, 2008
    #13
  14. synergo

    nebulax Guest


    I don't know if this would apply, but that series of Sennheiser
    headphones (the HD-600, -580, -565, and others) have notoriously bad
    headphone cables, especially in regards to where the wire plugs into
    the cups. My 565's will almost not pass a signal unless I jiggle the
    connectors on the cups just right. Contact cleaner can help, but the
    whole connection is still on the brink of shorting out at any time.
    Several companies (Cardas included) have made replacement cable
    upgrades for those phones, and it's supposed to make a dramatic
    improvement, both in the electrical connection and the sound quality.

    -Neb
     
    nebulax, Oct 7, 2008
    #14
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