Re: harmonics in my frequency response

Thanks Jeanette!  You are helping me understand, this is great.  The dips I
am seeing are not when I use the piano, it's when I analyze using the
Windows speaker analysis program RTA, running on my Windows laptop - I
connect my Windows laptop to a USB interface, then to an A/D and pci RME
Hammerfall optical interface into my tower Linux system - RTA plays a
"beep/sweep" containing all frequencies, into the Linux machine, out into
my crossover/speaker system, back thru a microphone into RTA.  I pick up
the sound up with a test microphone connected to the USB interface back to
the laptop PC, and the plot I sent is the result.  The dips are steep.  If
I look at the output at 1 octave resolution, it looks pretty flat, but at
1/24 resolution, I see the steep dips I mentioned before.   I have
microphone correction file in the mix; seems there are many places where
something might be going wrong.  I will experiment more and see what I can
learn about why I'm seeing these dips.

On Fri, Jun 30, 2017 at 6:50 AM, Jeanette C. <[email protected]> wrote:

> Hi John,
> at normal samplerate of 44.1kHz or 48kHz you will - most likely - get
> aliasing close to the Nyquest frequency, i.e. 22.05kHz or 24kHz,
> respectively. For a start, these aren't related to your buffer sizes.
> Seeing that you operate within the box, using software synthesizers, these
> should take care of it. I'm not aware of simple filters introducing
> aliasing. In the usual implementations that wouldn't make any sense.
>
> Have you tried recording your piano unprocessed and looked at that
> spectrum? Maybe those dips are just natural parts of the sound. When you
> apply a lowpass filter you can of course expect some sort of a dip, that's
> why you use it. I can't see your screenshots, since I'm blind, so I can't
> judge the steepness of the dips.
>
> You shouldn't need to apply a filter to protect your speakers tweeters
> with a decent audio input, and Pianoteqq is supposed to be very good these
> days. If you hear extreme peaks, it is more likely that your speakers or
> your room setup is suboptimal. Could you supply a short test recording of
> your piano with and without your processing?
>
> HTH.
>
> Best wishes,
>
> Jeanette
>
> --------
> * website: http://juliencoder.de - for summer is a state of sound
> * SoundCloud: https://soundcloud.com/jeanette_c
>
> There must be another way
> Cause I believe in taking chances
> But who am I to say - What a girl is to do <3
> (Britney Spears)
>

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