Music on the XO

Mitch Bradley wmb at
Tue Oct 30 14:04:22 EDT 2007

Seth Woodworth wrote:
> Slightly off of the conversational thread here but: Information on the 
> specific output spectrum capabilities might improve transcoding of 
> audio files into smaller file sizes.  If there is no, or poor quality, 
> auditory response below or above a given threshold, it might be worth 
> snipping off various frequencies, or otherwise optimizing how 
> materials are encoded to take advantage of this.

The speakers start rolling off at about 600 Hz and are virtually 
worthless below 400 Hz.

The hardware has a one-pole highpass filter at about 400 Hz (I forget 
the exact frequency but it doesn't matter much) in order to reduce the 
amount of useless LF energy that is presented to the speakers.  The 
rolloff is only in the speaker path; the headphone path has flat 
response across the audio band.

In my experience, equalization doesn't improve the sound from the 
speakers very much.  They sound tinny and weak no matter what you do.  
Taming the big peak in the 4 Khz range is of some value, but most 
program material has little information in that region, so the perceived 
improvement is small.  Boosting the bass makes things worse - the 
speakers don't have enough air-moving capacity (cone diameter times 
linear motion range) to render low frequencies, and sending them more 
signal just slams the mechanical structure against its physical limits, 
causing distortion and possible damage.

Bottom line - don't sell your Klipschorns.

> Is Jamendo, or anyone else, studying this?
> And Re: above conversation.  Yes, I would love to see ethnologists get 
> involved.  The at the moment I don't believe is a lack of effort on 
> anyone's part, but a lack of available material.  Go to most 
> university's music libraries and you will still find plenty of content 
> in vinyl format as opposed to cd-audio or digital formats.  Getting 
> recordings made or existing recordings released into the public domain 
> is an important project, and one of the main topics of a "What should 
> Wikipedia do with $100 Million dollars" thread about a year back.
> I believe that just about everyone is on the same page here as far as 
> what they would *like* to see on the OLPC.  In the meantime I think 
> that the current selections are far better than nothing..
> Seth
> On 10/28/07, *Jean Piché* <jean at <mailto:jean at>> wrote:
>     >
>     > If I may summarize, what you are saying is that:
>     >
>     > a) Given that this is about education, OLPC should be taking the
>     > cultural high road in terms of bundled music.
>     yes.
>     > b) The perception that acceptable licensing terms will be difficult
>     > to impossible to obtain should not get in the way of a)
>     yes.
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