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Rio Karma and iHP-120 measurements

post #1 of 10
12/3/03 at 6:29am
Thread Starter 
I don't have a "reference" soundcard, but here are some simple measurements of the iRiver iHP-120 and Rio Karma headphone outputs.

Testing methodology:

Karma: encoded test signal in 16 bit 44.1 khz FLAC files, volume full, into line in of a Turtle Beach Santa Cruz sound card.

iHP: same test signal file, in WAV format. volume full into same sound card.

Frequency responses were normalized by subtracting the loopback results (not completely valid...) Sampling done at 44.1khz, 16 bits (tried 48khz to see if there is downsampling too...) Volume on both units was set at full to minimize noise on input stage of the sound card (higher gain here lead to significantly higher noise). Full volume may have affected the Karma's response curves...

Here come the graphs, courtesy RMAA 5.1:

Frequency response:



Karma: +0.03,-0.21
iHP: +0.03, -0.07
loop: +0.01, -0.03

Slightly supressed highs on Karma...

THD:



Karma: 0.0080
iHP: 0.0051
loop: 0.0044

Dynamic Range:



Karma: 91.4 dBA
iHP: 90.9 dBA
loop: 88.0 dBA

Stereo Crosstalk:



Karma: -83.0 dB
iHP: -87.6 dB
loop: -87.3 dB

Intermodulation:



Karma: 0.011 %
iHP: 0.014 %
loop: 0.017 %

Noise Level:



Karma: -91.5 dBA
iHP: -90.9 dBA
loop: -88.2 dBA

Some time I'll get around to testing the Karma at a lower volume level. Enjoy.
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post #2 of 10
12/9/03 at 6:02am
Great info. Would you happen to have this info for the iPod as well?
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post #3 of 10
12/9/03 at 6:54am
Wow! Thanks for the carefully made measurements!

It would be interesting to see how the headphone outs behave on low-impedance loads simulating real headphones, such as 32 ohm, because that's what most players have their problems with (keyword bass response).

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post #4 of 10
12/9/03 at 7:01am
BTW, the Karma's slight treble roll-off (actually -0.6 dB at 20 kHz is negligible anyway) must not be seen as a fault -- since a smooth low-pass filter makes for a better time-domain (transient) response at the expense of absolute frequency linearity compared to a steep filter.

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post #5 of 10
12/9/03 at 7:41am
Thread Starter 
I actually wasn't trying to say the Karma was a bad performer... Just pointing out any noticable differences . I personally don't hear a big difference between the devices, but then again my hearing isn't up to the task of hearing the difference between a brick-wall filter and a smooth roll-off at those frequencies, and as you implied, a .5 dB roll-off probably won't even be noticeable with the ears of a bat.

Sorry, I don't own an iPod. The Karma is my wife's, so I had easy access I know a few people that have iPods, so I may try to snag one for a few minutes, but I doubt they'll let me borrow it for even that long.

I re-did the tests because the intermodulation measurements looked funky.

DAP test redo

It turns out everything is essentially the same (though there is a similar roll-off on the soundcard that I must have messed up originally by doing something beside a external loopback) but the intermodulation for the Karma is exactly the same as for the iRiver. Don't know what was going on the first time with that particular measurement.

Also, I will be building a rig to test these under load soon (as an extension of making a ER-4P -> 4S box.) I have access to an impedance analyzer (20Hz-100Mhz ) so I'll post measurements from my two sets of headphones too (KSC-50, ER-4P) once the rig is built to correlate any bumps in the response.

EDIT: fixed link, thanks JaZZ
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post #6 of 10
12/9/03 at 9:02am
Quote:
Originally posted by ASDFer
I actually wasn't trying to say the Karma was a bad performer... Just pointing out any noticable differences
True, and that's how I have understood you.

Here's the correct link to the edited measurements.

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post #7 of 10
12/9/03 at 6:13pm
WHAT DOES IT ALL MEAN!!?!?!?!?!


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post #8 of 10
12/9/03 at 6:25pm
It means that measurement-wise (within these common, simple measurements) these units are just about equal -- good frequency response, good distortion, excellent stereo crosstalk.
While these measurements do not tell the whole story, it means that these units have the possibility of being fine sounding units.
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post #9 of 10
12/9/03 at 6:35pm
I made some measurements of iPod a few months ago. I am fairly sure I have plain iPod measurements but the only thing I can find on my webspace is iPod plus PPA. iPod by itself is a bit better, especially with stereo crosstalk which I believe is flat in the whole frequency range.

http://members.shaw.ca/ifkovic/elect...0%2b%20PPA.htm
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post #10 of 10
12/9/03 at 8:10pm
Thread Starter 
One thing to remember is that results with different ADCs shouldn't be directly compared, except generally. Numbers will be different due to different noise/distortion characteristics of each sound card.
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