Re: FIR filters
Exactly – the power response is as the name suggests - the power emitted by the speaker. It does not account for directivity. If the “power” is emitted in all direction the SPL in front of the speaker will be relatively low, if you concentrate it in a small area (narrow pattern horn) then the SPL will be relatively high.
We generally listen to speakers in a reverberant environment. Raimond’s has used a target power response for correction which typically has 5dB to 6 dB boost in the low frequencies to account for the directivity. This can be modified as necessary. His argument is that this approach better represents what we hear in the field.
A little off topic -- It’s important to understand that what we are hearing (perceive) is different to what a microphone hears.
The part of the ear that contains the hair cells (basilar membrane) is a pseudo-resonant structure. Its behavior can be modeled with an auditory filter bank based on the gammatone function. This information is then sent to the brain which does it best to remove the thing we don’t want hear as part of its processing … it all gets very tricky but what we are perceiving is different to most measurements.
For measuring a speaker in the near field then Systune, Smarrt and TDA EQ all work fine. TDA EQ does give some good information about the time domain issues. Basically in the near field in an anechoic chamber you want flat.
Mechanics of the ear https://www.youtube.com/watch?v=TobHJt1jIHg
Gamma tone https://en.wikipedia.org/wiki/Gammatone_filter
power is the rate of doing work … J /sec = watts
