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iPhone 5 sound quality - Page 5

post #61 of 239
Thread Starter 

Do you think you can actually hear something at -75dB?

post #62 of 239

I can definitely heard the difference in the noise floor between earlier and later ipods. It's not even close. 

post #63 of 239
Thread Starter 

You would have to be listening pretty doggone loud, uncomfortably loud, for the difference between -75dB and -90dB even to get close to being audible. Are you using line out? Perhaps it's your amp you're hearing. If not, you may be damaging your hearing listening that loud.


Edited by bigshot - 2/2/13 at 7:40pm
post #64 of 239
Quote:
Originally Posted by bigshot View Post

Do you think you can actually hear something at -75dB?

Well, I can hear a sine wave at -75 dBFS, at normal listening volume wink.gif
Not a chance I would hear anything that quiet with real music though, which I assume is what you meant.
post #65 of 239
Thread Starter 

Not just -75dB.... Second harmonics at -75dB!

post #66 of 239
Quote:
Originally Posted by Trenn View Post

I can definitely heard the difference in the noise floor between earlier and later ipods. It's not even close. 

Quote:
Originally Posted by bigshot View Post

You would have to be listening pretty doggone loud, uncomfortably loud, for the difference between -75dB and -90dB even to get close to being audible. Are you using line out? Perhaps it's your amp you're hearing. If not, you may be damaging your hearing listening that loud.

 

What's -75 dB to -90 dB?  I thought that was harmonic distortion (2nd or 3rd order, so at -75 dB, pretty inaudible).  Trenn was talking about noise floor.

 

In the silence between sections or maybe before the beginning, a low level of noise from the electronics can easily be apparent with sensitive IEMs with high isolation.  Those things reach 130 dB SPL / 1V and higher, on many popular higher-end models.  For some scenarios, something less sensitive than that and even some full-size headphones would reveal some hiss as well.  That is, unless the noise in the recording is higher, which is often the case.  But that's not always the case, so it shouldn't be dismissed offhand or disbelieved.  Seems like the noise floor in general is more likely to be an audible issue than the harmonic distortion, for most reasonably-priced audio systems; that said, neither is likely a real consideration on speakers at typical levels in a noiser listening room.  Certain kinds of distortion are hard to hear because they're always masked by the original signal, the transducers may have plenty of it on their own, and so on.

 

Now, when the music itself is masking everything else, then no.

post #67 of 239
Thread Starter 

The noise floor of the original iPod was over -100dB if I remember correctly. If someone is actually hearing that clearly, they definitely have the volume turned up WAY too high.

 

Mountains out of molehills.

post #68 of 239
Quote:
Originally Posted by bigshot View Post

The noise floor of the original iPod was over -100dB if I remember correctly.

For a 16 bit device? Unlikely. My Classic measures at -95 dB, which is still very respectable 16 bit performance.
post #69 of 239
Quote:
Originally Posted by skamp View Post

For a 16 bit device? Unlikely. My Classic measures at -95 dB, which is still very respectable 16 bit performance.

Noise measurements are generally made with a weighting filter (A-weighting is typical), which would easily put the figure below the theoretical -96dB for 16 bit unweighted noise.
post #70 of 239

A Weighting is good for about 3 dB improvement to an unweighted noise figure. 

 

The larger point I wanted to make was that there have been substantial measurable improvements to iPods over the years. Personally, for 2nd and 3rd order distortion, I can't hear anything lower than -45 dBc, and for 5th to 7th, I can't hear anything lower than -70 dBc. So, I'd suspect most can't hear the THD differences between first and latest ipod. 

 

From a noise perspective, the fact that I can put a 24-bit flac or other lossless format onto a modern iPod, while I couldn't on an older ipod, is important from a quality perspective. There's a very good picture at the website I linked above that shows the noise performance for an mp3 versus flac. Even on a modern ipod the difference is huge. It is 25 dB if the graph is to believed. So, consider a modern flac file that is well recorded, with a nominal at -25 dBFS and peaks to 0 dBFS. That file squeezed to a 16-bit file format would be crushed. 

 

http://www.quantasylum.com/content/Portals/0/Blog/Files/1/23/Windows-Live-Writer-Apple-Ipod_8B2D-image_38.png

post #71 of 239

Not sure how noise at -120 dB instead of -145 dB is an issue for audio intended for human listening.

 

Unless you specialize in listening to amplified silence.

post #72 of 239
Quote:
Originally Posted by Trenn View Post

A Weighting is good for about 3 dB improvement to an unweighted noise figure. 

Not true.  It can result in many different improvements in a noise measurement  depending on noise spectrum...which is the point of a weighting network. 

Quote:

Originally Posted by Trenn View Post

 

The larger point I wanted to make was that there have been substantial measurable improvements to iPods over the years. Personally, for 2nd and 3rd order distortion, I can't hear anything lower than -45 dBc, and for 5th to 7th, I can't hear anything lower than -70 dBc. So, I'd suspect most can't hear the THD differences between first and latest ipod. 

 

 

Interesting statement.  How are you "measuring" these figures?  Are you actually generating some form of distortion or are you trying to simulate harmonic distortion by summing sine waves at different frequencies and levels?

 

Quote:

Originally Posted by Trenn View Post

 

From a noise perspective, the fact that I can put a 24-bit flac or other lossless format onto a modern iPod, while I couldn't on an older ipod, is important from a quality perspective. There's a very good picture at the website I linked above that shows the noise performance for an mp3 versus flac. Even on a modern ipod the difference is huge. It is 25 dB if the graph is to believed. So, consider a modern flac file that is well recorded, with a nominal at -25 dBFS and peaks to 0 dBFS. That file squeezed to a 16-bit file format would be crushed. 

 

http://www.quantasylum.com/content/Portals/0/Blog/Files/1/23/Windows-Live-Writer-Apple-Ipod_8B2D-image_38.png

 

After digging around on the quantesylum site, I could find no background information for the test image above.  If there is some somewhere, please post a link.

post #73 of 239
Thread Starter 

AAC is audibly transparent after a certain bitrate. I think the first iPod plays ALAC files too.

post #74 of 239
Quote:
Originally Posted by bigshot View Post

The noise floor of the original iPod was over -100dB if I remember correctly. If someone is actually hearing that clearly, they definitely have the volume turned up WAY too high.

 

Mountains out of molehills.

 

dBV?  dBu?  dB ref. max signal output (though I think for an iPod, that's 1V so equivalent to dBV pretty much)?  A-weighted I guess?

 

If the absolute noise level does not decrease much when the volume is turned down, then it's not so much somebody having the volume turned up too high, but that some sets really are that insanely loud and sensitive, and it's a challenge to actually accommodate that.  Take down the volume 50 dB or so (I've done more before) so peaks are at maybe 85 dB SPL, and noise could be riding at 20-35 dB SPL, or however it scales.  Maybe these people should just be using low-noise external amps and turning the volume down there?  But that's an extra hassle to carry, and would be an admission of defeat for the original player device.

 

Sometimes there really is some kind of "amplified" silence in the middle of music, and some people could be bothered by noise from the electronics during it.

 

Probably not a big deal at all, especially to the majority of users who don't meet this corner case, but to a certain point I wouldn't trivialize an improvement in noise levels.  As long as it doesn't really cost extra, or much extra, why not?

post #75 of 239
Thread Starter 

I'm talking about line out. Headphone out is going to vary.

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