Testing freerunner's audio quality

Dr. H. Nikolaus Schaller hns at goldelico.com
Thu Sep 23 06:47:10 CEST 2010

the problem is the bass. Initially, It was difficult to hear differences
by playing two sounds one after the other. So until you have listened
music on a bass fixed Freerunner, you would say it is quite ok.

I was only able to hear the difference after taking one original Freerunner
and one with Bass-Fix applied. After a while you get that there *is* a
difference in low frequencies.

What I have done is this test: create a sinus sweeping from 10 to 100 hz.
Without bass fix you can't hear it before it comes to the 50 hz range.

sox -n -t wav - synth 10 sine 10-100 >file.wav

This can be seen on scope outputs as shown here:


Can you please compare you device?

One effect may also be the input impedance of your line card. Did you connect
it in parallel to a headset?


Am 22.09.2010 um 23:57 schrieb Gennady Kupava:

> Hi, list, 
> Many gossips flying around about bad fr's audio subsystem quality. I
> promised to proove that FR audio subsystem is good, just default
> headphones quality below anything.
> As today finally i overcome my lazyness and soldered 2.5mm->3.5mm jack,
> and i am almost content with high sound quality of my  Sennheiser CX300
> II+FR, i decided to do some basic testing.
> Test environment
> ================
> I got 2 recodings - 60 seconds of white noise and 120 seconds of piano
> +voice, audacity to do spectrum analisys, cable 3,5mm<->3,5mm to connect
> my old m-audio revolution 7.1 card to line-in to freerunner.
> White noise
> ===========
> 1. White noise were generated by audacity original file:
> http://www.bsdmn.com/openmoko/audioquality/white.wav
> Spectrum:
> http://www.bsdmn.com/openmoko/audioquality/whitenoise.png
> 2. Same noise recorded then audio-out were connected to audio-in of
> sound card:
> http://www.bsdmn.com/openmoko/audioquality/rec_white_directcable.wav
> Spectrum:
> http://www.bsdmn.com/openmoko/audioquality/whitenoise_direct.png
> 3. Same noise played on FR, connected to line-in of sound card:
> http://www.bsdmn.com/openmoko/audioquality/rec_white_fromfrerunner.wav
> Spectrum:
> http://www.bsdmn.com/openmoko/audioquality/whitenoise_fr.png
> Conclusion on white noise:
> I see no frequency cut-offs. spectrograms look very well and close to
> original file. Only exception is fall below 20Hz in fr case, but i am
> unsure if any headset can reproduce such frequences very well.
> Real song
> =========
> 1. Original piece of song (piano+voice):
> http://www.bsdmn.com/openmoko/audioquality/song.wav
> Spectrum:
> http://www.bsdmn.com/openmoko/audioquality/song.png
> 2. Same file played on freerunner and captured on line-in of sound card
> http://www.bsdmn.com/openmoko/audioquality/rec_song_fromfr.wav
> Spectrum:
> http://www.bsdmn.com/openmoko/audioquality/song_fromfr.png
> Conclusion on piano+voice:
> I can't distingush difference in quality while replaying original file
> or file recorded from freerunner. Spectrum show almost no difference.
> Overall conclusion
> ==================
> Seem audio quality completely depends on quality of headphones. You may
> try to distiguish original song and song from fr youself, only do not
> forget to normalize volume before attempting to do this.
> regards,
> Gennady.
> _______________________________________________
> Openmoko community mailing list
> community at lists.openmoko.org
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