filo97s
Active Member
i know what it means and i know how to calculate it, as many of you here i'm an electronic and telecommunication engineerAgain different bandwidth. Maybe you don't know what that means. I'll elaborate.
These two tests are THD+N tests. Meaning the noise is a very important part of the number. The N (noise) is the accumulated noise of BW * N0 or intergral of noise at all individual frequency. Thus, higher BW = higher noise = higher THD+N.
Why amir chose 90khz for thd+n vs frequency test. He chose it because the distortion after around 7khz will go down due to bandwidth limit, 3rd harmonic of 8khz which is 24khz for example will not show up in the thd+n vs frequency test if bandwidth is set to 22khz. However this leads to the first issue the number is constantly higher.
There maybe way around it like thd no n vs frequency, separate spectrum of 10khz etc. But generally you only need to look at dynamic range, use it to calculate noise floor, and the multitone test. That's all you hear in real world.
Since what we hear is only in the 20-20k band, i think it's better to set a standard for BW for all measurements, i know that in this way in thd vs freq. there's a lot that won't show up since harmonics go past 20k, but who cares after all? For me it's better to have consistency between measurements, it's the way I choose for all my measures, and i thought that even the 1k thd was at the same BW. Or if you prefer, use the 90k bandwith even for the 1k test. However it doesn't matter, I had the answer for my question, I thought the Bw was the same.