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September 14, 2010

iPod nano

Barely larger than the shuffle, the iPod nano packs the same 4 gigabytes as the original mini, but it's flash, not hard disk. The screen is color, it shows pictures, but you already know all that. The real question: How does it sound?

In terms of overall frequency response and lack of distortion, it's right up there with the very best players. In terms of bass response, it's the second-best player I've ever heard or tested.

The nano takes a back seat to the shuffle in sheer bass performance, but it's still well ahead of any of the large iPods, and has a slight edge over the Zen Micro. It's the equal of the Archos PMA400, which is saying something.

The overall sound is open and spacious, it has that unconstrained sound of flat frequency response and generous amounts of power. That generous power extends down to all but the lowest frequencies, where it bagins to tail off:

This is a logarithmic sine wave sweep, which is an easy test for the player's electronics, but very demanding at the lowest frequencies. As you can see, response tails off. The player would do this dead flat if the earbuds weren't plugged in, but their load is especially severe at the lowest frequencies. Measurements like this are typically taken 10dB below the clipping level, as these were. The nano was very impressive in that once it came up to the -10dB level and stayed within a couple of tenths of a dB all the way through the rest of the sweep, instead of dancing around a fair bit, as most players do. There may not be any audible benefit, but it shows that the amplification is very accurate across the spectrum.

Here's another look at frequency response, with white noise instead of sine waves:

White noise spreads the power around randomly and evenly through the spectrum, so the amount of power at any given frequency is lower than a sine wave would be at a single frequency. So without having changed the volume control, the level drops. As you can see, it's below the "sag" level at the lowest frequencies, so the response is flat. Is it loud enough? Oh yes. but if we were to crank the player's volume up, the curve would begin to look like the previous one, sagging in the bass.

The shuffle, by comparison, remains dead flat.

Here's that most evil of tests, the 40Hz square wave, first unloaded:

As you can see, it's essentially perfect. Now let's plug in the earbuds:

Unlike the shuffle, the output stage is analog, and gets pulled down. But as I've observed elsewhere, any player that doesn't get pulled all the way to zero sounds pretty darn good and has enough power to drive earbuds at reasonable listening levels. This waveform is comparable to the Zen Micro and Archos PMA400, and if anything, the nano sounds a bit livelier.

There's one more way we need to look at the tone--in a full-frequency spectrogram. This is the view that reveals harmonic distortion, and in nano's case, with the EQ turned off/flat, there is none:

The thin, red line is the -10dB signal as it sweeps through the audio spectrum; the yellow and green down low is the lower output at low frequencies. There's not a hint of harmonic distortion. This is very clean.

Now let's turn on one of the EQ settings:

This is bass boost, and you can see that the nano increases the amount of fundamental (the red line fading into orange down low), but also adds several harmonics to sounds below 200Hz to fool your ears into thinking there's even more fundamental frequency. It sounds convincing, but it also adds intermodulation distortion up high. It's less prevalent here than in many other players, but it's still there and audible as a very faint sizzle around bells, triangles, and similar high, clean tones.

Every EQ setting adds its own blend of distortion, meant to fool your ears in different ways. No small players have true tone controls; of the players I've tested, only the Archos PMA400 actually adds and subtracts frequencies in a specific range instead of playing around with psychoacoustics.

I found the nano to be utterly enjoyable with flat EQ, and it appears that with the improved low-end power, the designers were able to take a lighter hand with the psychoacoustic manipulations. So if you decide to use an EQ, you won't hear out-and-out distortion and crappy, artificial-sounding music, as you would on many other players.

The nano is a winner, and a more-than-worthy successor to the mini.

Posted by machrone at 09:34 PM | Comments (7)