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Topic: iPod Classic Sound Quality

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Old 09-13-2007, 08:16 AM
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iPod Classic Sound Quality

Being a bit disappointed about the iPod Classic sound quality, I've performed some measurements, and compared it with the iPod Video 5G:
http://www.hifivoice.com/audio/ipod/...surements.html

The results show that the iPod Classic has some problems with amplitude, phase and linearity as compared to the iPod Video.

Marc
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Old 09-13-2007, 09:18 AM
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uii... weird... i tested yesterday with my shure headphones and noticed no difference (the expensive tipple driver ones) odd odd.

Cant test again because I just sold my 60GB 5g one. Somehow I doubt apple engineers would release an ipod with such obvious mistakes, moreover the iloung (maybe bias) review mentions no worse sound quality.
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Old 09-13-2007, 09:29 AM
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I haven't heard too much, if any difference with my shure e4c's but I sent feedback to Apple requesting improvement anyway. Couldn't hurt.



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Old 09-13-2007, 10:36 AM
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Quote:
Originally Posted by germanjulian
uii... weird... i tested yesterday with my shure headphones and noticed no difference (the expensive tipple driver ones) odd odd.

Cant test again because I just sold my 60GB 5g one. Somehow I doubt apple engineers would release an ipod with such obvious mistakes, moreover the iloung (maybe bias) review mentions no worse sound quality.

I don't think they would do it deliberately but the second generation shuffle definitely doesn't sound as good as the first generation model. Different hardware inside I believe that makes the difference so it's always possible that the innards are different thus making a difference in sound quality. If that is the case I won't be upgrading because I am v. happy with the sound quality from my 60gb video.
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Old 09-13-2007, 11:40 AM
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Thanks for the tests.

Yes engineering charts do not lie and it looks like Apple needs to do some work.
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Old 09-13-2007, 12:43 PM
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Quote:
Originally Posted by Astro_Digital
Thanks for the tests.

Yes engineering charts do not lie and it looks like Apple needs to do some work.
Actually they can if the tests are not done correctly. Not that I am doubting this users tests, however he even states that he is doing the tests on the headphone jack unloaded. You need to provide a proper load in order to do signal tests such as these.

Before these tests can be believed without doubt they must be duplicated by another person independently. I would if I had access to both a 5G ipod and an oscilloscope.

Curious how the 4G ipod would stand up? Cause I noticed a marked improvement (by ear) in sound quality between the 4G and the classic. The 4G had some very noticeable issues.
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Old 09-13-2007, 01:27 PM
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Quote:
Originally Posted by m1abrams
You need to provide a proper load in order to do signal tests such as these.
The line-out of the iPods reveal the same results, so the sanity check in that field have been applied.

I've also applied different windows over the measurements, I re-did the stimuli, and double checked with a M-Audio Mobile Pre. Too much details to mention to make the main point, so I left it out.

The technical measurements are consistent with the things that I hear.

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Old 09-13-2007, 01:31 PM
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These graphs are nice and all but the real question is if any of these decreases in audio output can actually be heard. We call all plot frequencies of a 192kbps VBR AAC file up against a lossless file and we know how they will look. The lossless file will look like the sound quality is just out of this world and that the lossy file sucks. That doesn't mean anything though since we can't really hear the difference.

Almost all reviews that I am reading say that the audio quality output has been increased. I don't know their testing methods but they all seem to agree so it must have some merit. I myself didn't notice too much of a difference between the two. I have a expensive pair of headphones that use two 3.5mm inputs (one for left and one for right). I hooked up both my 5G 60GB iPod and my iPod classic to the headphones and played the same song encoded at the same setting (-V 2 --vbr-new Lame 3.97). I couldn't readily hear a difference between each channel so I was satisfied. I know that is not the best way to hear a difference between something but it worked for my mind.



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Old 09-13-2007, 03:31 PM
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Quote:
Originally Posted by kornchild2002
These graphs are nice and all but the real question is if any of these decreases in audio output can actually be heard.
For that there is literature, e.g. Fastl and Zwicker, Psychoacoustics. They mention that differences in the order of 0.2dB or 10 degrees phase shifts can be heard. The differences described in the book are created in a controlled manner, and not because of non linearities in the circuitry, which is even worse.

I also read that in many cases people cannot hear the difference. One pitfall is that you should align the playback volume carefully, as volume differences do affect the perception drastically. Also, for some instances of headphones (dark sounding headphones) or music it might seem to be a good chance in the first go, but overall it is not so good. And finally, with some listening experience and engineering experience it is easier to distinghuish what is going on, and also to find the root cause.

Something that is erroneous can be pleasant in some specific cases (e.g. an old tube radio with some old recordings of Ella Fitzgerald), but in general it will disappoint. I think that this is an important observations.

Anyhow, the measurements support the observations, that are recognized by many. So I hope Apple takes this issue seriously.

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Old 09-13-2007, 04:11 PM
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One of the wonders of the internet age is that problems like this are rumbled so quickly, and with the assistance of experts like Marc Heijligers and sites like iLounge the news is disseminated just as fast.
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Old 09-14-2007, 03:11 PM
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I have a fifth-generation iPod and I just bought the iPod Classic, 80GB, three days ago.

Not sure whether it is just a psychological thing, I seem to notice a difference in the sound produced by the two iPods. The new iPod Classic seems to drop a few elements in the same song played by the fifth-generation iPod. I wouldn't say it sounds lousier or better. Just that I think the iPod Classic sounds "cleaner"? But, on the other hand, I think the fifth-generation iPod sounds "richer". I think it is a matter of getting used to it.
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Old 09-14-2007, 04:45 PM
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Quote:
Originally Posted by MarcHeijligers
For that there is literature, e.g. Fastl and Zwicker, Psychoacoustics. They mention that differences in the order of 0.2dB or 10 degrees phase shifts can be heard. The differences described in the book are created in a controlled manner, and not because of non linearities in the circuitry, which is even worse.

I also read that in many cases people cannot hear the difference. One pitfall is that you should align the playback volume carefully, as volume differences do affect the perception drastically. ...

Marc
You are correct in that there is literature out there that describes it all and tells of many audible cases. However, I must attest that the majority population probably cannot hear these differences as they are not all audio engineers or sound experts. In fact, most people's hearing is limited to what the 128kbps VBR iTunes AAC format can produce. Whether they admit it or not (through blind ABX tests, everything comes out), their ears just aren't fine tuned.

You make a very good point about audio volume. Often times, people perceive a higher volume to be of higher quality. That is why many modern day CDs are mastered crapily because they simply increase the volume of certain low frequency instruments thus giving the illusion of high quality.

Back to the audio differences, I just don't think that the majority of people will hear a difference and if there is a difference, it is probably very slight in terms of the overall population noticing. I don't really think it is an issue that Apple needs to fix. I myself cannot tell if I hear a difference between my 5G 60GB iPod and my 160GB iPod classic. The only true way to tell is to hook them up to two audio inputs and use headphones. Then switch between each iPod as they are playing the exact same song at the exact same volume. I think I might be able to hear a difference but it could very well be the placebo affect as I do not have equipment that can do a ABX test.



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Old 09-14-2007, 05:06 PM
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Quote:
Originally Posted by MarcHeijligers
For that there is literature, e.g. Fastl and Zwicker, Psychoacoustics. They mention that differences in the order of 0.2dB or 10 degrees phase shifts can be heard. The differences described in the book are created in a controlled manner, and not because of non linearities in the circuitry, which is even worse.
Marc
I find it hard to believe that anyone can detect a 0.2dB difference - I would think it would have to be above 0.5dB. I know for a fact that my 50+ year old ears just can't detect this kind of difference. Of course, in my younger (& stupider) days in the late 60s/early 70s, was way too often right in front of a big stack of speakers for Mountain, The Allman Bros. Band, The Who, Yes, etc....

I've never tried a blind ABX test between 2 iPods - it was difficult enough to set up one for comparing CDs to MP3s. The volume match is the tough part. I'll eventually get a 160 Gb classic (my 60Gb 4G is already not big enough) - I'll try a true blind ABX test when I get it & see what I think. Problem is, my ears are just too old to really judge the difference in an objective sense - but really only care about how I perceive the sound.
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Old 09-14-2007, 05:17 PM
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Quote:
Originally Posted by kornchild2002
You are correct in that there is literature out there that describes it all and tells of many audible cases. However, I must attest that the majority population probably cannot hear these differences as they are not all audio engineers or sound experts. In fact, most people's hearing is limited to what the 128kbps VBR iTunes AAC format can produce. Whether they admit it or not (through blind ABX tests, everything comes out), their ears just aren't fine tuned.
Of course, there are indivuiduals who can't distinguish, or are not interested.

There is quite some difference between audio encoding and electronic circuitry if it comes to audibility. Many of my friends cannot distinguish a 128kbit/s from a 256kbit/s compressed file, even if the 128kbit/s contains extreme artifacts like flanging and pre-echoes. Nevertheless, the same persons are capable of distinguishing the differences between output circuitry.

There is also music for which 128kbit/s suffices, and the output circuitry can still be a dominant contributor to the sound quality perceived.

Quote:
Originally Posted by kornchild2002
Back to the audio differences, I just don't think that the majority of people will hear a difference and if there is a difference, it is probably very slight in terms of the overall population noticing. I don't really think it is an issue that Apple needs to fix.
I disagree completely with you here. The iPod is a collection of features, of which sound quality is one. I know of a lot of people around me (non-audiophiles/audio engineers!) that choose another device because of sound quality. Whether their choice is valid in terms of sound quality is debatable (sometimes they choose for a "brand"), but sound quality is pretty high on the list. Ignoring is one, but decreasing the sound quality from previous versions is quite a disappointment so to say.

Quote:
Originally Posted by kornchild2002
I myself cannot tell if I hear a difference between my 5G 60GB iPod and my 160GB iPod classic.
The differences are quite noticable. Just take a recording of a jazz combo and chamber ensemble in a concert hall or big room, and listen to the spatial field and the way cymbals attack and decay. Then, listen to for instance a fado recording (female voice), and compare the "edge on the voice". Finally, take a rock song with strong cymbals, and listen how metallic the overall sound perception is. It's quite easy to recognize.

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Old 09-14-2007, 05:49 PM
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do u guys think this can be fixed with a firmware update or no way cause its hardware.
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