nick mineau wrote: ↑Wed Jul 14, 2021 9:10 am
...which way should i measure my subs to compare to a TEF chart like danley uses? flat db peak, or flat db regular/rms?
do bills charts use 2.83v 1 meter db peak or rms/none peak?
I'm gonna stick my neck out and say RMS on both accounts...
I did a quick search through the SMAART User Guide and found this...
SMAART User Guide wrote:Full Scale (dB FS) versus Full Scale
There exist two competing references for decibels in digital audio signals. One convention references dB
FS to the largest positive and negative amplitude values obtainable from a given integer sample word
size – e.g., ± 32768 for 16 bits – normalized to a range of ± 1.0, such that 0 dB FS denotes the maximum
possible digital amplitude value. We will refer to this as “normalized Full Scale.”
The second convention, preferred by the Audio Engineering Society (AES), references 0 dB FS to the RMS
value of a full-scale peak-to-peak sinewave (i.e., 0.7071 normalized Full Scale, rather than 1.0). We will
call this “AES Full Scale”. In Smaart, Full Scale decibel values are always referenced to normalized Full
Scale, meaning that the RMS magnitude of a full-scale digital sinewave is -3.01 dB FS.
I've got to imagine, being the AES "preferred" value, that anything from a reputable manufacturer would (should) be the RMS value. And any professional software or hardware measuring equipment (such as TEF) would more than likely also follow those guidelines and default to RMS. Although, from what's written above, I'm not clear whether SMAART defaults to RMS (AES Full Scale) or not. It reads as though they default to Peak. So, a little wishy washy.
Not 100% definitive, but my best educated guess is RMS would be the correct value to use for comparing to other standard response charts.
Side note FYI, when you measure an AC voltage with your DMM, the number you see on the screen is RMS voltage which uses the same 0.7071 factor... 70.7% of peak to peak voltage = RMS Voltage. So, a wall socket that shows 120v is actually 169.7v peak to peak... which, non-coincidentally is a 3.01dB difference.