[sdiy] Experiment with bandlimited ramps

[Seb Francis]

Tom Wiltshire wrote:
> Hi All,
>
> I've done some experiments generating bandlimited ramp waves at 
> various frequencies and with various numbers of harmonics. The results 
> (lots of sound files - page loads fairly slowly) are at:
>
> http://www.electricdruid.com/index.php?page=thoughts.bandlimited
>
> The idea was to find out practically how many harmonics are required 
> for an accurate additive synthesis. Since by the time you're at a 5KHz 
> fundamental, you'd be lucky to hear the 5th harmonic, I started at 
> about 85Hz. These low notes need the most harmonics to sound good.
>
> Have a listen and see what you think.
>

Have just had a listen of the bass tones in my studio and I can hear 
barely any difference between 100 and 150.

This is interesting since I can hear a marked difference between these 
same tones when listening on my laptop speakers with built in sound 
card.  And JH also said he can hear a dramatic difference between 100 
and 150 (what were you listening with JH?)

In the studio, I'm listening through high-end RME D-A converters, £3000 
monitor speakers (ADAM S3A) and also Sennheiser HD-650 headphones (and 
with good ears :)  I can assure you that under these circumstances there 
is no dramatic difference between 100 and 150.  The difference is ultra 
subtle and only in the very high frequencies.

What are the frequencies of these top 50 harmonics anyway Tom?

Many PC sound cards perform internal resampling (e.g. to 48kHz), so 
perhaps this is causing the difference JH noticed and that I hear on my 
laptop?

Seb