FR vs True Peak

[camplo]

I have reason to believe that the FR measurement isn't showing true peak spl.. anyone know the exact details?
According to my research, a sine waves true peak is 3db over rms, and from my experiments, I believe that the FR that REW records is rms spl, not true peak.

edit: Answered my own question

 

[camplo]

I guess the real question is how to get the measurement to read True Peak, in order to properly judge THD...

 

[camplo]

@John Mulcahy Feature request, respectfully. True Peak FR/THD readings.

 

[John Mulcahy]

how to get the measurement to read True Peak, in order to properly judge THD

Why? THD is derived from rms levels.

 

[camplo]

Can you explain please? THD has RMS and True Peak, no different than the fundamental. THD can be viewed as RMS or True Peak no different then the Fundamental signal. So it would make sense to Display THD as true peak if displaying the Fundamental as true peak, is what I am saying. I don't even know if this is possible since I have not come across any program that will show FR measurements as True Peak anyway. If you can't create fundamental signal measurements from True Peak then you can't create THD measurements following True Peak. If you can create FR measurements from true peak, you can create THD measurements from true peak.

 

[John Mulcahy]

THD has RMS and True Peak, no different than the fundamental.

No, it doesn't. THD is a metric, not a signal. It is calculated from the rms levels of the fundamental and the harmonics, see the definition.

 

[camplo]

THD is a metric, not a signal.

Hi, this is a quote from the link you shared " THD is a measure of that additional signal content not present in the input signal."

Once again, True Peak - "A true peak, in the context of audio signals, represents the absolute maximum value attained by the signal waveform, irrespective of its duration." The Fundamental signal the additional signals that are known as THD have RMS values and True Peak peak values.
It would be so great to be able to access to True Peak measurements of both, signal types, available. Yes REW calculates its THD from RMS values, but I do not see why True Peak values cannot be an option. Also, I know of no software recording such data but as a loudspeaker designer it would very useful.

 

[John Mulcahy]

That quote: "THD is a measure of that additional signal content not present in the input signal." Check the definition of a metric.

The peak value of a signal over a duration is a single number that captures the signal level at one instant within that duration (interpolated from oversampled data in the case of digital true peak monitoring). Your comments about "True Peak" are nonsensical. There is "no software recording such data" because it conveys so little information as to be pointless.

 

[JLM1948]

Hi, this is a quote from the link you shared " THD is a measure of that additional signal content not present in the input signal."

Once again, True Peak - "A true peak, in the context of audio signals, represents the absolute maximum value attained by the signal waveform, irrespective of its duration." The Fundamental signal the additional signals that are known as THD have RMS values and True Peak peak values.
It would be so great to be able to access to True Peak measurements of both, signal types, available. Yes REW calculates its THD from RMS values, but I do not see why True Peak values cannot be an option. Also, I know of no software recording such data but as a loudspeaker designer it would very useful.

Can I ask you a definition of THD True Peak? What do you expect from it? As a loudspeaker designer, I fail to understand what additional knowledge it would benefit you.