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iPod classic tests reveal audio problems

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By Charles Starrett

Contributing Editor
Published: Thursday, September 13, 2007
News Categories: iPod

Newly released audio measurements comparing the iPod classic to a fifth-generation iPod suggest problems with the newer iPod’s Cirrus Logic audio codec. Having initiated a discussion in Apple’s iPod classic forums, Marc Heijligers writes, “The measurements show is that the iPod Classic indeed has an uplift in treble, and its timing response is incorrect.” According to Heijigers, the new Cirrus Logic audio codec chip, which Roth Capital’s Jay Srivatsa says has replaced a chip from Wolfson Microelectronics inside the iPod classic, misaligns the arrival of treble detail relative to mids and bass, causing audio from the classic to lack “spatial information and a certain timbre.” Heijligers suggests that Apple may be able to fix the problem through a firmware update.

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Comments

1

Will this affect the Nano, and or the Touch? Did they use these chips in all the Lines. Now I’m wondering about my touch preorder

Posted by Scarpad on September 13, 2007 at 9:36 AM (PDT)

2

This is not good. I sure hope Apple acknowledges and fixes this problem quickly. Nothing worse than fancy new iPods with degraded audio quality.

Posted by coolfactor on September 13, 2007 at 9:46 AM (PDT)

3

Now this news will backfire on Ipod classic.They should leran something from sony or bose.They are the kings when it comes to sound quality.

Posted by vivian mascarenhas on September 13, 2007 at 10:04 AM (PDT)

4

I agree this is very bad and Apple will need to fix this promptly by a firmware update!

However, I don’t really think I have noticed any difference in sound on my new classic and I actually think the sound is a little bit better than the 5G, so to those who are considering not getting one after this news article, you really have nothing to worry about; especially if Apple ARE going to fix it with a firmware update.

Posted by ‹-cJr-› on September 13, 2007 at 10:09 AM (PDT)

5

My classic sounds fine to me with Shure e3c in-ear monitors. Most of the reviews I’ve seen have pegged it has having very similar to better audio quality than the 5G iPod.

Posted by Mike on September 13, 2007 at 10:28 AM (PDT)

6

spacial issues ARE a big deal when it comes to audio, regardless of what some reviews are mentioning thus far.  kinda disappointing that apple got this wrong.  lately it’s been really poor, consumer unfriendly decisions when it comes to features…  but this sounds like carelessness.  Why wouldn’t internal testing reveal audio integrity falling outside of the norm?

Posted by spimp31 on September 13, 2007 at 10:41 AM (PDT)

7

Most people won’t care, as they listen to 128K audio through the crap pack-in earbuds.  That’s how Apple continually gets away with this nonsense.

Sound quality has been on the decline ever since the first shuffle, which against all reason had simply amazing quality.

Posted by malren on September 13, 2007 at 10:58 AM (PDT)

8

That’s not the only issue.  Various changes in functionality are apparent between the Classic and the 5.5gen, notably including:

1. Play Count and Last Played fields are not incremented when playing songs on the Classic and/or not synced to iTunes

2. There is no longer an option to hide compilation artists from the Artists list, causing massive clutter in a decent-sized library.

3. Random ejects when connected to a computer.

4. Mine, at least, came Windows-formatted, and attempts to restore to Mac format took several hours, largely due to issue #3, above.

5. Inability to turn off the clock/battery screensaver that now kicks on after a minute of playing, meaning you can’t see what’s playing on the iPod without rolling the wheel or pressing a button.

6. General sluggishness of the OS - it takes seconds to move around in the Playlists section on my unit.

I’m pretty disappointed, to be honest.  I’ve owned a 1G, 3G, 4G, 5G, two minis and two shuffles, and this is the first iPod I’ve owned with such significant issues in functionality.  I assume all can be changed with a firmware upgrade; I hope one is forthcoming.

Posted by Simon on September 13, 2007 at 11:07 AM (PDT)

9

i can’t be agree with that, my new classic 160 gb sounds better than my old 60gb.

Posted by gonzalo on September 13, 2007 at 11:08 AM (PDT)

10

i’m glad someone found out, was about to buy the 160gb classic this weekend now i better wait… it sounds like a hardware problem, sure it can be fixed, not sure if this can be fixed via firmware update though

Posted by named on September 13, 2007 at 12:43 PM (PDT)

11

“There is no longer an option to hide compilation artists from the Artists list, causing massive clutter in a decent-sized library.”

I have around 70 compilation albums (together with around 800 others). Without the ability to hide the compilation artists, my artists list would be utterly unmanageable.

Posted by Joshua on September 13, 2007 at 1:00 PM (PDT)

12

The number of missteps that seem to have happened with this new line of iPods should be utterly emberassing to Apple.  From the Nano, Classic and Touch it seems like they may have rushed too many products to market at once. 

How about another Apple event take 2 in January where they really roll out the new line of iPods for real this time - all of this seems like a bad dream…..

Posted by notagain on September 13, 2007 at 2:19 PM (PDT)

13

“3. Random ejects when connected to a computer.”

I had this same problem - turned out to be a bad USB cable.

Posted by Mike on September 13, 2007 at 2:25 PM (PDT)

14

Knowing how irony likes to rear its ugly head ...  watch, there will be a firmware update for the audio problem only to then discover that battery life had to be sacrificed.  heh!

Posted by Rod on September 13, 2007 at 2:47 PM (PDT)

15

Did anybody actually read Mr. Heijligers report? This issues he finds are trivial at best. The “treble rise” is contrasted to a slight treble loss on the 5.5g iPod, and both are approximately 0.1dB deviations from perfect - a unit so small I guarantee that it cannot be heard.

Recall that 1dB is DEFINED as the smallest change that a human can perceive. 0.1dB is a variation far smaller than batch discrepancies in any group of identical speakers or headphones you care to name.

Furthermore, the so-called “incorrect timing response” is EXACTLY what one SHOULD see given a small change in treble response - this is systems engineering 101, folks. The time and frequency domains are different reflections of the same behavior.

This “timing response” is far more linear than any mechanical device (speaker, headphone) you will find on the planet.

As to spatial effects - well, any that exist in 2 channel recordings are subject to an awful lot of much larger forces, such as room acoustics, headphone behaviors, and a lot of psychology. Spatial data simply is so poorly represented in 2 channel audio that when it seems to work it is often as not a fluke - the data just isn’t there in a reliable form. When we have recordings that actually represent multi-channel, multi-direction room reflections and multi-channel, multi-direction playback systems we might have something, but not today.

I did enjoy his graphs. Note that the vertical scale is in 0.1dB increments so as to make these tiny deviations visible at all.

IMHO this is truly nothing.
Cred: BSEE @ MIT, 1989

Posted by BradPDX in Portland, OR USA on September 13, 2007 at 4:21 PM (PDT)

16

I should apologize to all the audio experts here. I don’t have the fantastic ears that you all have. I’m just content to just have something to that holds the music and podcasts I listen. I guess I was wrong. I should train my ears to be able to hear those uplift in treble and to listen for ‘degraded audio.’

Posted by Jim of D on September 13, 2007 at 5:37 PM (PDT)

17

Thank you so much, BradPDX, for putting this into perspective. I, like several others, also haven’t noticed any significant quality problems. Granted, I typically use cheap earphones (not because I don’t like good sound, but because I don’t like spending lots of money on things that can break/get lost easily… I use my iPod all the time and everywhere), but I still think it sounds great.

I haven’t noticed the play count issue. That’s a real bummer. I really hope they fix that one.

I haven’t had the random eject issue.

The screen saver would be better if it could be toggled, but I don’t think it’s a big enough deal to complain about.

The OS can be sluggish at times, but I attribute this to the artwork. It’s got to load that stuff, and I love the GUI way too much to care about a slightly slower interface over my 4g 20gb.

Posted by Isral DeBruin on September 13, 2007 at 5:37 PM (PDT)

18

Re: “1dB is DEFINED as the smallest change that a human can perceive.”

The decibel is not defined by human hearing. It is a logarithmic scale of power ratios. However, research has shown that the smallest acoustical power changes that humans can perceive are between 0.5 and 1.5 dB.

Cred: college drop-out

Posted by beetsnotbeats on September 13, 2007 at 6:13 PM (PDT)

19

The audibility of phase deviations and amplitude deviations depend on their context. The figures of 0.5 to 1dB originate from research concentrating on the audibility of level changes based on noise or single frequency signals, and hardly on variations in timbre.

The type of deviations described are backed up by many where these are audible (e.g. the sonic differences of a Butterworth or Besselfilter, showing only 0.1dB passband ripple deviations in their passband).

The true cause for the iPod audio behaviour needs investigation inside the iPod circuitry or signal processing, before any conclusions can be drawn. The measurements show that there are differences, especially non lineairities in phase behaviour. These are commonly known as very audible.

Posted by Marc Heijligers on September 14, 2007 at 9:59 AM (PDT)

20

Re: “1dB is DEFINED as the smallest change that a human can perceive.”

My bad. Excuse me there, I should have noted this as 1dB SPL, with 0dB defined as the threshold of perception. Nonetheless, your note indicates that the 1dB figure for change (and you are right, dB is all about ratios) is the approximate figure for minimum human perception, which is quite a bit more than 0.1dB - 10 times in terms of shear amplitude. As the human ear is far more sensitive to certain sections of the audio spectrum than others, this figure is accepted as a good rule of thumb.

I will add that the human ear is far less sensitive to amplitude changes at frequencies outside the range of speech.

As to the audibility of phase shifts (especially those less than 360 degrees) this is widely debated. The human ear is certainly more sensitive to large shifts in midrange (vocal) frequencies where speech is concentrated, but sensitivity at high frequencies has not be convincingly demonstrated in the literature I am familiar with - especially on typical “real” sounds like music, which are rich in multiple phase representations of each source.

I leave open any possibility, but my own experience suggests that phase audibility of the type discussed here is minimal.

Posted by BradPDX in Portland, OR USA on September 14, 2007 at 11:58 AM (PDT)

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