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Apple lossless and bass rolloff on ipod

Discussion in 'Headphones, Earphones & Portable Music' started by johnpmiles, Jun 1, 2005.

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  1. johnpmiles

    johnpmiles
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    Hi!

    I'm waiting to receive my ipod photo, and have decided to encode some of my CDs with ALE. The others I'll use AAC for, and use AACgain to allow the EQ to sort the infamous bass rolloff problem.

    My question is:

    Is there any way to use Apple Lossless and avoid bass rolloff whilst not resorting to higher impedance headphones? I'm using Shure E2Cs.

    Please don't just tell me to get a different player! :)

    Thanks in advance.
     
  2. mick's cat

    mick's cat
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    Can you provide a decent link about the supposed iPod bass roll-off? As far as I can find, it's just an urban myth started from dubious subjective origins and I've never seen a properly conducted test and report.

    Having said that, the iPod earbuds have a 32 ohm impedance while the E2Cs have a 16 ohm impedance, so the potential for lost bass does exist. However, from all reports I've seen (again subjective, of course) the iPod's output - even with the European volume capping - drives the E2Cs perfectly well. I don't think you'll be disappointed, and I don't suppose ALAC will give any better results than AAC. I'd be interested to hear what your personal results are when you get your iPod though.
     
  3. johnpmiles

    johnpmiles
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    Thanks for your reply. The article I looked at was here:

    http://www.dapreview.net/content.php?article.133

    As you, say, it's difficult separating myth from reality on this issue. I'll be sure to report back in a couple of months when my aunt arrives from the States with my ipod.
     
  4. David Mackenzie

    David Mackenzie
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    What is "bass rolloff"? Is it an inability to reproduce sounds with high bass?

    If that's what it is then it's anything but a myth. My iPod G4 20gb had this, which is why I got rid of it. Even on great headphones that sounded great on everything else, I got the "rumbly bass" effect.
     
  5. mick's cat

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    Yes, I've seen this before, but I've also seen others on other DAPs that show the same sorts of rolloff. It's all personal in the end, and I think you might be pleasantly surprised when you get your iPod. It's not at all as bad as some people suggest...
     
  6. mick's cat

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    Roughly, yes, but a little more complex than just that. The aim of any audio amplifier is to reproduce sounds of all frequencies within the human hearing range of about 20Hz to 20KHz as equally as possible. Bass rolloff is where the amplifier fails to do so at the lower end of the frequency range. A listener might detect a 'lack' of bass notes if this is perceived. All amplifiers exhibit bass rolloff to some extent, as do they exhibit treble rolloff - which might sound like high frequencies are missing to a listener. They are both facts of life of an audio amplifier.

    The problem is that many factors can affect the rolloff. Lower impedance output transducers for example, mean that the amplifier is working harder at certain frequencies. In the case of a DAP, the output transducers are the earphones, and so the particular earphones used can make a big difference to the perceived sound.

    Quantifying rolloff is not easy, as listener detection of it is such a personal thing. Some people like a 'flat' sound, while others like what is - effectively - exaggerated bass and treble. I'd go as far as saying that historically, hifi patricians tend to aim for a flat sound in all thing audio (which is one possible reason why the iPod has fared so well recently in comparative reviews of DAPs) while the rest of us plebs prefer more bass and treble. That's why most audio amplifiers have bass, treble, equalisers, dynamic sound generation and the like. Personally, as far as the iPod is concerned I like the relatively flat sound, and the wide range of eq settings for different music types, but I can see where other DAP users are coming from when they say they like more bass. A better pair of earphones could just make the difference too, as some are much better at reproducing bass and treble frequencies than others.

    And talking about earphones, I still wonder whether there's a correlation between earphones and ear sizes. If the earphone fits properly, then sound will be much better. If it's loose then bass frequencies will not sound as loud as they should. It's not a factor that I think many people consider - with most DAPs the earphone is the cheapest part, yet the most easily upgradeable.

    Sorry everyone if this got a little off-topic.
     
  7. extremelydodgy

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    The iPod bass falloff is not myth. In my experience it affects headphones of below 50-60 ohms to different degrees. The Line Out is unaffected with line loads, so attaching an amp to the line out will not generate a sound with bass falloff.


    Koss clip-ons and headphones typically have an impedance of 60 ohms, which will get around the problem. Even imported from the US, they're pretty cheap. For bigger phones, the Sennheiser HD25-1 is also a higher impedance phone, as is the Beyerdynamic DT250-80. The choices exist in good numbers if you look around. The other solution is to use a low impedance headphone which has almost too much bass to begin with (Sennheiser HD212, Sony MDR-V700DJ, Sennheiser PX100, etc) and live with the bass falloff.


    The last solution is to increase the impedance on your existing phone by using an in-line attenuator, such as that sold by Shure for the E5. This WILL however change the sonic characteristics of your phone, and it may be even pointless as the increased impedance might reduce the bass response of the phone, which would render the recovery of bass response from the iPod moot. I haven't checked what increased impedance would do to the E2c's sound... I'd have to check it out.


    Either way, the falloff exists. It's a separate issue from sound quality though, as the iPod is a pretty good source for a portable. Aside from the problem, it has good dynamic range (with a much larger selection of phones than... oh let's take a particually bad example, the Sony HD1/3/5), good precision and a useful range of codecs, something that many in-production players can't boast. However I'm concerned to note some problems with the photo iPods. Not having one, I can't confirm that they do actually distort the audio signal... but it seems to have been a problem with engineering in the video output to the headphone jack. I don't know if the problem still exists.
     
  8. mick's cat

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    The iPod's earbuds are 32 ohm, which is an odd specification for Apple to choose given your experience. Whether rolloff is what some other listeners refer to as tinny though is still debatable. And we can't forget that all other DAPs suffer from it to some extent, although some I'm sure try to cover it by enhancing frequencies at the amplifier stage.
    I heard this was a first production run concern, but I don't know for definite.

    If all iPods go (which is rumoured) to the new sound chip as used in the shuffle, this may all be moot when the new models come out, as this seems to be significantly better all round. And it's all relative after all - the iPod sound as it stands still gets the thumbs up in recent reviews over others. Personally, though I can tell there *is* a difference between Apple, Sony and Creative DAPs (which after all, total over 98% of the DAPs sold), I simply couldn't say one is any *better* than another. Maybe my old ears are just giving out.
     
  9. extremelydodgy

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    It is an odd decision by Apple, because there is definitely a falloff with low impedance phones to a much larger extent than any other player I've had.


    Having said that, the ibuds are perhaps the MDR-V700DJ of earphones, rather excessively mid-bassy. This does overcome the falloff... However, there's been another cock-up there too. The ibuds are a little larger than many earbuds, to the extent that it at best wedges in some ears (especially women) but doesn't fit properly to deliver the optimum bass. So yes, in many ears they can sound tinny because it's not fitting properly.


    Although they may have achieved iconic status, IMO Apple definitely shot themselves in the foot with the design details of the ibuds.
     
  10. Steven

    Steven
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    I've just been thru a thread over at head hi-fi on this............
     
  11. extremelydodgy

    extremelydodgy
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    So?


    Anyway... E2c results. At 125 ohm combined impedance (so that's 109 ohm effective added resistance), there is no discernible bass fall-off in an A-B switch comparison to an iRiver H300 series. Even at 70 ohm-ish though we're talking less than a couple of dB's falloff (try it in iTunes, Winamp or Foobar... 2db or less reduction at 30-40hz) at most at the lowest of the low frequencies. Since it's a US iPod, you won't need to do any firmware bodges to fix the volume and even at 125 ohms, the E2c's can be cranked to deafening levels. On the other hand, if you want to keep things manageable about 60-80 ohms should be fine. The range of very noticeable faloff point seems to be sub-60 ohms, and especially sub-40 ohms.


    Is the sound of the E2c affected by added impedance? I didn't have much time to devote to this, but I would say that there might just be a tiny, tiny loss of 'air', a sense of space. Since the E2c isn't an incredibly 'airy' phone to start with, it might be an issue... but then it might not be.


    Either way, I'd suggest picking up the Shure inline attenuator and starting from there. Attenuate the signal a little, and turn up the iPod to compensate. You're now loading the iPod with additional impedance at the headphone jack. THe only flaw with this is that the rotary attenuators used devices which look like the Shure usually are pretty crap, so there's a lot of channel imbalance as well as other nasties. I haven't tried the Shure one so I don't know if it's good, but these adjustable attenators are useful in allowing you to decide how much additional impedance you do want to add before actually making an 'impedance adding plug/socket combo'.
     
  12. johnpmiles

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    Thank you Extremelydodgy for your very helpful post. I'll continue to look into this. The other option I've considered is getting a portable amplifier like the supermini/maxi moy. Perhaps that would be a good move...
     
  13. extremelydodgy

    extremelydodgy
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    That would unfortunately defeat part of the portability thing, but sonically it would be a good move in assuredly getting rid of the bass falloff and to lend some additional authority to the sound. The Etymotic ER-4P > S converter is also an option if you want to keep it ampless.
     
  14. johnpmiles

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    I think an amplifier will be an eventual upgrade to treat myself to in the future. For the time being, I think i'll get the Shure variable pot. Just one more question:

    Does anyone know the resistance range of a Shure level attenuator?
     

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