Can I subtract a measurement from another ( difference ) ?

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redmountain

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• Oct 10, 2024

• #1

as the title says...
?
Thanks

Klaus

 

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linuxonly

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• Oct 10, 2024

• #2

Hi,

It's readily available in the Beta version: Trace Arithmetics -> A-B

 

John Mulcahy

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• Oct 10, 2024

• #3

In 5.31 you can find trace arithmetic from the All SPL graph.

 

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redmountain

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• Oct 11, 2024

• #4

Yes
but
A-B doesn't reflect the actual difference in dB
i.e.100dB@100Hz - 90dB@100Hz I would like to see as
-10dB@100Hz
Hope to be clear...

Thanks

Klaus

 

John Mulcahy

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• Oct 11, 2024

• #5

Subtraction of dB values corresponds to trace division.

 

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redmountain

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• Oct 11, 2024

• #6

This I don't understand...

 

John Mulcahy

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• Oct 11, 2024

• #7

dB traces are produced from the log of the underlying data, for magnitude responses the trace values are 20*log10(data values). log(A/B) = log(A) - log(B), i.e. division of the underlying data sets corresponds to subtraction of the logs of their values.

 

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redmountain

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• Oct 11, 2024

• #8

sorry, that is to much for me
Thank you anyway !
It would be great for me to have an arithmetic difference shown between 2 measurements, defaukting on a flat 'zero +/- line
Best regards

Klaus

 

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linuxonly

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Preamp, Processor or Receiver

Logitech Z906

DAC

AMD FCH Azalia

Computer Audio

SPDIF output with alsa, pipewire, wireplumber on Fedora 40

Streaming Equipment

Kodi

Front Height Speakers

33 in

Middle Height Speakers

30 in

Rear Height Speakers

57 in

Video Display Device

X11/VGA + X11/DVI

• Oct 11, 2024

• #9

redmountain said:

sorry, that is to much for me
Thank you anyway !
It would be great for me to have an arithmetic difference shown between 2 measurements, defaukting on a flat 'zero +/- line
Best regards

Klaus

Click to expand...

Hi,

Like John told you in https://www.avnirvana.com/threads/c...ent-from-another-difference.14245/post-107978 , use trace arithmetics -> A/B
Don't tick 'max gain'

 

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redmountain

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• Oct 11, 2024

• #10

Thank you
I misinterpreted A-B
A/B means A divided by B here
A-B means A subtracted by B

Sorry...

 

John Mulcahy

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• Oct 12, 2024

• #11

redmountain said:

It would be great for me to have an arithmetic difference shown between 2 measurements, defaukting on a flat 'zero +/- line

Click to expand...

Use this:

 

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redmountain

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• Oct 12, 2024

• #12

Yes
linuxonly told earlier
Thank you
and all the best

Klaus