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Topic: iPod Equalizer issues...

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Old 10-08-2004, 04:04 PM
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iPod Equalizer issues...

Can anyone shed some light on the iPod's equalizer implementation? I have the following questions:-

(1) Does the equalizer rely on digital signal processing -- changing the wave form of the data stream -- or does it act on the analog output?

(2) I have noticed that using the equalizer frequently result in "clipping" that sounds similar to CDs which have exceeded the dynamic range of its 16-bit audio format. Sort of like a blown speaker except that it seems to be volume and headphone independent, as the same distortion is heard whether the volume is at 25% or 75%.

(3) I have noticed that the aforementioned distortion can be mitigated or eliminated in wav files by "Normalizing" to a low peak level (say 60%). This suggests that the EQ is digitally causing peak dynamic range to be exceeded. Unfortunately, it seems that MP3 encoders artificially level the volume level during encoding so feeding them 50% normalized wavs and un-normalized wavs seem to result in tracks that are idenitcal in loudness. I have also noticed inconsistent volume levels throughout the track if I feed the encoder wavs that have been normalized to a very low peak level (say 20%). LAME 3.90.3 is used within EAC for the experiments using a command line input of "--vbr-old -q 0 -V 0 -m j -b 192 -c %s %d "

(4) It seems moronic that whoever implemented the EQ can even allow somethig like that to happen. We all know that CD tracks -- especially today's CD tracks -- have peak levels very close to or at 100%. In fact there are a lot of moronic recording engineers who accepts some considerable amounts of "clipping" just so the CD will play "louder". Nonetheless, if the iPod is performing the EQ digitally, shouldn't it only CUT levels at particular frequencies but never EVER add levels? The same EQ shape can be achieved via a reduction only implementation and such a scheme will never blow through the dynamic range. Any volume reduction can be compensated for simply by the user uping the volume.

Last edited by dwightlooi; 10-08-2004 at 04:14 PM.
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Old 01-06-2005, 10:37 AM
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Re: iPod Equalizer issues...

Quote:
Originally posted by dwightlooi
(4) It seems moronic that whoever implemented the EQ can even allow somethig like that to happen. We all know that CD tracks -- especially today's CD tracks -- have peak levels very close to or at 100%. In fact there are a lot of moronic recording engineers who accepts some considerable amounts of "clipping" just so the CD will play "louder". Nonetheless, if the iPod is performing the EQ digitally, shouldn't it only CUT levels at particular frequencies but never EVER add levels? The same EQ shape can be achieved via a reduction only implementation and such a scheme will never blow through the dynamic range. Any volume reduction can be compensated for simply by the user uping the volume.
Sorry to bump such an old thread, but it's better than starting a whole new thread with the same question ...

I've just found a song which basically sickens me to listen to on my iPod, and I'm trying to figure out how to make it sound decent. The song is "Ventolin [Deep Gong Mix]" by Aphex Twin. This song has a LOT of *very low frequency* bass, I did an analysis on the .wav file and saw that the main beat is peaking at about 45Hz, which is very low.

Unfortunately, the iPod is incapable of playing that LF bass on low impedance phones, like my Shure E5c, and Audio-Technica ATH-A900. I mean, it's there, but it's rolled off a bit. So, I tried using the "Bass Booster" EQ setting. That setting is UNUSABLE with this song, there is a HORRIBLE amount of clipping, it's really horrendous. I've MP3Gain'd all of my songs, including this one, to a conservative 89.0db, but even at that level, the iPod is still clipping the hell out of the 20Hz-200Hz range. It's unbearable.

So, I've decided to look elsewhere when I buy my next MP3 player. All it would take is a customizable EQ to make me love my iPod again, but Apple seems to have their collective head up their a$$ as far as that goes. I'd even be content using the preset EQs if, like the original poster discussed, the same EQ shape was achieved by DROPPING certain frequencies, rather than BOOSTING some. Whoever designed the EQ system on the iPod deserves to be fired, it's really a horrible implementation.

ARGH.



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Old 01-06-2005, 11:25 AM
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my unhelpful tip, dont listen to that song.



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Old 02-06-2005, 07:02 PM
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I'm surprised this critical issue is seemingly largely ignored by the iPod community.

To me this seems crippling. I always like to listen to my music with a little warmth and bass, and found that the "Dance" setting is great... for the few songs that don't happen to go clipping crazy when I use the EQ.

Maybe we can petition for a different EQ implementation via firmware? Because as of now, to me the iPod has to have one of the worst EQs/audio quality I've ever experienced.
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Old 06-22-2005, 03:33 AM
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Re: iPod Equalizer issues...

Quote:
Originally posted by dwightlooi

(4) It seems moronic that whoever implemented the EQ can even allow somethig like that to happen. We all know that CD tracks -- especially today's CD tracks -- have peak levels very close to or at 100%. In fact there are a lot of moronic recording engineers who accepts some considerable amounts of "clipping" just so the CD will play "louder". Nonetheless, if the iPod is performing the EQ digitally, shouldn't it only CUT levels at particular frequencies but never EVER add levels? The same EQ shape can be achieved via a reduction only implementation and such a scheme will never blow through the dynamic range. Any volume reduction can be compensated for simply by the user uping the volume. [/B]
I think you've hit the nail right on the head. I definitely agree that the EQ is being applied digitally at the pre-amplifier stage, however I don't believe the actual file's waveform is being edited in real-time to reflect the desired EQ preset. I believe it's more of a gain-stage (preamp and amp sensitivity) issue than the actual dynamic range of the file being disturbed, although virtually, the same results do occur.

I have found that if you apply a preset on the Pod and it clips at certain frequencies, it continues to clip at these same frequencies at a proportional level when the volume is reduced. This, obviously, is evidence of preamp clipping. The internal amp then amplifies the clipped signal it's receiving and sends it to the headphones. A good way to demo this is to go into iTunes EQ on the computer and crank the preamp level with an EQ setting applied. Eventually it will clip despite the volume level, and this is what we're seeing on the iPod.

I also concur with your statement about level cutting. The problem is that the amp on the iPod is hardly capable of properly amplifying a signal that has certain frequencies cut.

The bottom line is that the gain stage between the preamp and the amp needs work, as well as the power of the amp itself in order to make this problem more bearable. When this occurs, EQ settings should be altered to cut frequencies, as you've said, rather than boost them.

If I had known to do my research on this issue before I bought the iPod, I NEVER would have made the purchase. Apple's implementation of its EQ profiles is disheartening to me at the very least and definitely shows its lack of care and touch with the audiophile community. It's definitely something that will have me looking around in the future before I jump on the bandwagon.

Last edited by Helix26404; 06-22-2005 at 03:38 AM.
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Old 06-22-2005, 03:49 AM
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You know, every time I see posts like this, I just don't get it.

Nowhere does iPod advertise itself as an "audiophile's MP3 player". It's all good that you guys are into this stuff so hardcore, but you must understand that I, and the vast majority of the iPod users in the world, have NO idea what the hell you are talking about, except at the most abstract level.

Seriously, with my very limited understanding of this, can ANY compressed format of music really satisfy hardcore audiophiles? Can any format of digital music, even, truly satisfy?

You make it sound like Apple and their purchasers are being screwed... but really... 99%+ of iPod users really don't place these kinds of demands on their audio hardware. It's like hardcore vinyl fans in 1983 laughing at the quality of the average Walkman.
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Old 06-22-2005, 04:01 AM
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Quote:
Originally posted by dharmabum420
You know, every time I see posts like this, I just don't get it.

Nowhere does iPod advertise itself as an "audiophile's MP3 player". It's all good that you guys are into this stuff so hardcore, but you must understand that I, and the vast majority of the iPod users in the world, have NO idea what the hell you are talking about, except at the most abstract level.

Seriously, with my very limited understanding of this, can ANY compressed format of music really satisfy hardcore audiophiles? Can any format of digital music, even, truly satisfy?

You make it sound like Apple and their purchasers are being screwed... but really... 99%+ of iPod users really don't place these kinds of demands on their audio hardware. It's like hardcore vinyl fans in 1983 laughing at the quality of the average Walkman.
First, I want to clarify that I understand that the iPod is not marketed as such, and I apologize if I came across that way. Like I said in my previous post, I should have done more research, especially considering that I am so particular when it comes to this. I guess I expected too much out of this device, and that is no one's fault but my own.

To partially answer your question and provide more info for the thread, audio compression, in the sense that you have referred to it, has relatively little to do with the problem that the iPod has. For instance, I can set the EQ on the iPod to flat (or off, for that matter), and hook it up to my car stereo, which is EQed and tuned to my taste, and the sound is AMAZING, just like a CD or something similar. This is actually what has convinced me to keep the iPod. However, when simply connecting headphones which have no independent EQ control, you have the choice of a stale, flat EQ signal, or a distorted mess when applying the EQ settings.

I simply responded to this thread because I, like the poster, have noticed some of the EQ problems that the iPod currently has. It's good to know that I'm not the only one with questions.
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Old 06-22-2005, 04:10 AM
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To add:
Quote:
It's all good that you guys are into this stuff so hardcore, but you must understand that I, and the vast majority of the iPod users in the world, have NO idea what the hell you are talking about, except at the most abstract level.
I wasn't aware that being annoyed about obvious distortion made you "into this stuff so hardcore". It certainly doesn't make you any more "hardcore" than participating in a forum about iPods.

This flaw doesn't affect me personally, since I don't really care about the equalizer that much, but I wouldn't want to generalize and say that since I don't care, the vast majority of iPod users must not either.


Quote:
Seriously, with my very limited understanding of this, can ANY compressed format of music really satisfy hardcore audiophiles? Can any format of digital music, even, truly satisfy?
Not everyone who's annoyed by the iPod's bad equalizer is a hardcore audiophile. A friend of mine commented that it made his music sound "fuzzy", and he uses old Sony wrap-around headphones. I told him that was clipping, and now he can't stand to use the built-in equalizer.
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Old 06-22-2005, 04:25 AM
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Well, SDA, you hadn't posted in this thread 'til this point, so it's safe to say I wasn't talking about your post directly... or anyone's, really, just when I see these threads devolve into technical speak I, and most people, have no understanding of.

I just know one thing; I have over 6,000 songs on my iPod, I'm using $35 headphones, I have virtually every genre I can think of on my iPod for which I use the pre-programmed EQ settings depending on the music, mostly in 192kbps MP3, and I've never been unhappy with the way my music sounds.

It's fair to say that the iPod's EQ usage could be improved, but I get annoyed when people think they've been screwed because everything they demand out of audio fidelity isn't precisely addressed by a player designed to cram as much compressed music as possible into it. Sure, it's something that Apple can improve along the way, but it takes a backseat to things like gapless playback that the large majority of iPod users (who really don't know how to use the EQ at all, in my experience) desire.

Maybe my ear isn't as "tuned" as others, but I love music, I play a half-dozen instruments, and I know music. I just wonder at what point the concern for perfect fidelity overrides consideration of what the music is saying... I get choked up when listening to "Tom Traubert's Blues" whether it was on vinyl, tape, CD, or 192kbps MP3 on an iPod, and that's all that matters to me.

Last edited by dharmabum420; 06-22-2005 at 04:28 AM.
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Old 06-22-2005, 04:43 AM
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Quote:
Well, SDA, you hadn't posted in this thread 'til this point, so it's safe to say I wasn't talking about your post directly... or anyone's, really, just when I see these threads devolve into technical speak I, and most people, have no understanding of.
I know, I'm not treating it as a personal thing. Like I said, I rarely even touch EQ (never on my mini, and I'm not really bothered by that).

Let me put it in less technical terms for you: usage of the equalizer on the iPod will cause audible distortion. The higher up any bar in the equalizer is, the worse the distortion will be. If that's still too technical, I don't know what to say. Look up distortion?


Quote:
I just know one thing; I have over 6,000 songs on my iPod, I'm using $35 headphones, I have virtually every genre I can think of on my iPod for which I use the pre-programmed EQ settings depending on the music, mostly in 192kbps MP3, and I've never been unhappy with the way my music sounds.
Quote:
Maybe my ear isn't as "tuned" as others, but I love music, I play a half-dozen instruments, and I know music. I just wonder at what point the concern for perfect fidelity overrides consideration of what the music is saying... I get choked up when listening to "Tom Traubert's Blues" whether it was on vinyl, tape, CD, or 192kbps MP3 on an iPod, and that's all that matters to me.
No offense meant, but your personal experience is largely irrelevant. The problem is there, and easily perceivable to non-"audiophiles".

Comparison: I know people that are happy with Windows ME. This is an extreme example, but it proves a point: just because one person in particular is happy with what they have does not mean that problems with that product don't matter or aren't noticed by most people.

Your personal experience is especially irrelevant when you consider that people in this thread are annoyed by this problem. The fact that you are not does not cancel this out.



Quote:
It's fair to say that the iPod's EQ usage could be improved, but I get annoyed when people think they've been screwed because everything they demand out of audio fidelity isn't precisely addressed by a player designed to cram as much compressed music as possible into it. Sure, it's something that Apple can improve along the way, but it takes a backseat to things like gapless playback that the large majority of iPod users (who really don't know how to use the EQ at all, in my experience) desire.
It's not even an "everything they demand out of audio fidelity" thing, though. It's very easy to design and implement an EQ that does not behave in this way, which is why nearly every other manufacturer has done it. You seem to think that an EQ that doesn't suck is some kind of expensive, difficult-to-implement feature that most people don't even care about.

Last edited by SDA; 06-22-2005 at 04:49 AM.
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