WHAT ABOUT THE SOUND (subjective impressions)? Given the less-than-friendly user interface, weird USB jack, etc. there must be some other reason people pay $120+ for these, right? I’ve read it's the sound quality. Before measuring the i9 I spent some time listening to some of my favorite music with a variety of headphones and I was reasonably pleased with the sound. With most of the headphones I tried, it played loud enough for my tastes and didn’t have any obvious sonic flaws.
COMPARISONS: Without any EQ (the only fair way to directly compare the two), the i9 didn't sound obviously better than my iPod Touch. Getting the iPod's clean sound in a smaller/cheaper package isn't a bad thing but what about the Sansa Clip+? It’s even smaller and cheaper than the i9. Using very high-end headphones, and some of my favorite highly revealing acoustic tracks of music, I wasn’t sure I could hear any obvious differences with the Clip either. That's not to say there are none, but they don't stand out in a casual comparison at normal listening levels.
AUDIBLE HISS: Playing back a really low signal with my most efficient headphones (UE SuperFi's) the Cowon i9 had some audible hiss but it wasn't objectionable. It's about the same as the Clip+. It was, however, more obvious than the Touch 3G's noise level. With more typical headphones the hiss will likely be inaudible.
THE MEASUREMENTS: More detailed results are presented below, but here's the brief summary:
- Frequency Response: With a typical load, the i9 starts rolling off in the bass at 100 hz until it's about 4.2 dB down at 20 hz. That's a significant roll off and is much worse than the iPod or Clip+ both of which stay ruler flat all the way down to 10 hz. With good headphones and the right music, this is likely audible and would make the Cowon sound a bit weaker in the deep bass. Above 100 hz the response is fine.
- Distortion: At typical listening levels, THD+N distortion was roughly 0.02% from 20hz to 1 Khz, but rose to about 0.4% at 10 Khz. This is decent but not great performance. It’s fairly similar to the Sansa Clip+ overall with the i9 doing better at 1 Khz and the Clip doing better at 10 Khz.
- Maximum Output: The i9 has higher than average power output--about 2 dB higher than what the iPod can manage into the same load. It delivers roughly 24 mW into 16 ohms. This gives the i9 a bit more "headroom" for inefficient headphones or those who like their music really loud.
- Output Impedance: The Cowon is better than average here. The output impedance was about 1.5 ohms which should keep frequency variations with even some of the more wild headphones to within +/- 1.5 dB or so.
- DAC Performance: The square response was clean but the DAC linearity was a bit off at low levels and the i9 might have higher than average jitter. So the DAC results are kind of mixed.
NO HEADPHONE AMP REQUIRED: Unlike many portable players, the i9 should drive most reasonably priced portable headphones, and perhaps even some of the more difficult ones, to reasonable levels without audible problems. The relatively high power and low impedance should mean it's compatible with a wider range of headphones than most portable players. In fact, using a headphone amp with the i9 might make things worse instead of better by creating noise and/or volume tracking problems. See: Headphone Amps & DACs
i9 vs CLIP+: If a person doesn’t need the higher output of the i9 I think the Clip+ is a better player overall. The Clip+ has much better bass response, less high frequency distortion, and otherwise very similar performance for about 1/3 or 1/4 the price. The Clip also runs the excellent Rockbox firmware, is smaller, and doesn’t require buying an armband to wear on your arm (shirtsleeve). If that extra few dB of output power is important to you, or you’re just in love with Cowon’s particular choices of EQ or some other unique i9 feature, than I’d say go for the i9.
i9 vs iPOD TOUCH 3G: The iPod has much lower distortion across the spectrum and also lower noise and arguably better DAC performance. And with the $3 EQu app, it offers impressive EQ. The Touch of course also runs iOS apps, plays games, has bluetooth, WiFi, a much bigger screen, etc. But, the flipside is it’s bigger, heavier, more expensive, generally requires iTunes, won’t play FLAC files, is missing several of the i9’s features, and has a higher output impedance which makes it a bit more fussy about what headphones you pair it with. With typical dynamic headphones, if audio quality was the main focus, I’d likely pick the iPod over the i9. For higher-end balanced armature headphones, however, the Cowon or Clip+ would be my pick.
BOTTOM LINE: The Cowon i9 delivers fairly respectable audio performance but it's by no means at the top of it's class. Even the smaller and cheaper Sansa Clip+ outdoes it in some significant ways. And I'm not crazy about the user interface or proprietary USB jack. To me, it doesn’t do enough better than the Clip+ to justify its higher price, higher hassles, and potential performance problems.
TEST RESULTS (for those who are curious about detailed audio measurements, or just like to geek out on the numbers and graphs):
FREQUENCY RESPONSE: In my opinion, this is the i9's weakest measurement. It's generally considered players should manage +/- 1 dB from 20 hz to 20 Khz to be considered "flat enough" and "accurate". I can even live with +/- 1 dB from 30 to 15 Khz. But the Cowon is down 1 dB way up at 50 hz and it's down over 4 dB at 20 hz. That's a significant roll off in the bass and one that's likely audible under some conditions. It's worth noting this graph in yellow below is roughly what you'll get with most 16 ohm headphones. Higher impedance headphones won't create as dramatic of roll off. This is likely because the output of the Cowon's headphone amp is capacitor coupled and Cowon simply didn't use a big enough capacitor for either space or cost reasons. It's a relatively inexcusable design error in my opinion. Here's the graph:
The red trace above is the frequency response with no load. You can see the Cowon behaves much better here and is virtually flat. That's why I believe the roll off is caused by a poorly chosen output capacitor (or the presence of one at all--the iPod and Clip+ apparently have none which is even better). Here, to show how RMAA can mess things up, is the RMAA result with the exact same load and volume setting:
While RMAA confirms about the same low frequency roll off, note how RMAA shows a high frequency roll off when the dScope result above it does not. It starts around 10 Khz and falls off a cliff right before 20 Khz. This is likely a result of RMAA's multi-tone analysis being flawed. But I have verified the i9 does not roll off the way RMAA claims it does in the high frequencies. RMAA is also supposed to set its own relative 0 dB level which is generally done at 1 Khz. But it fails to do so accurately sometimes (like above). All this stuff is "automatic" in RMAA and, unlike with a real audio analyzer, the RMAA user has little control over any of it. It either delivers good results or it doesn't. And without anything to compare RMAA results to, you never know if the results are correct or not!
DISTORTION: The i9's distortion was fairly typical for a decent player at 1 Khz. Here's the THD+N and spectrum:
THD+N of 0.01% is very likely inaudible and the spectrum doesn't show any ugly surprises. Distortion usually rises with frequency and the Cowon rises a bit more than some other players (like the Clip+). Here's the dScope result at 10 Khz at the same typical listening level of ~ 180mV RMS:
THD+N of 0.4% isn't awful but it's way than the Clip+ and much higher than the Touch 3G. Here's the RMAA plot of the i9 versus frequency:
Note RMAA shows 3 times the THD at 1 Khz and slightly less THD at 10 Khz compared to the dScope but it does generally confirm similar results. I’m not sure what’s going on above 10 Khz but it’s likely an RMAA problem, not the i9.
And here's the swept IMD result showing somewhat worse, but similar, numbers:
DISTORTION SUMMARY: Overall, the i9 distortion results are only average. The i9 is similar to the much cheaper Sansa Clip+. And it's vastly worse across the board compared to the iPod Touch 3G. See my comments in the distortion section of the Sansa Clip+ review for more background on distortion measurements. It’s likely the i9 doesn’t have any seriously audible distortion problems.
MAXIMUM OUTPUT: Here the i9 does really well and delivered an impressive 624 mV RMS into 15 ohms at about 0.2% THD+N. This is about 24 mW into 16 Ohms which is about 2 dB louder than either the Clip+ or Touch 3G can play into typical 16 ohm headphones. 2 dB isn't a lot but it's noticeable. Here's the i9 at it's maximum output below 1% THD+N:
DAC LINEARITY: See the Sansa Clip+ review for some background on why this matters, but it's one common measure of the quality and implementation of the DAC in a portable player. The i9 didn't do as well as the Clip+ or iPod here. The -90 dBFS test signal measured -95 dBFS on the i9. This may cause some dynamic audible distortions when listening at low levels but they're not likely to be very objectionable.
TEST DETAILS: The i9 was running the latest V1.14 firmware from May 2010.