@617 is not wrong. Please lose the holier-than-thou attitude.
Anechoic chambers cannot provide reliable data at the lowest frequencies. Nearfield or ground-plane can.
Blend those techniques with gated measurement for frequencies > 0.5-0.8kHz, and results comparable to anechoic measurements can be had.
Trust me that I've tried to optimize the presentation within my time and location restraints
ANSI 2034 (and spinorama) is not about sub-100Hz data as all graphs anyhow converge there.
As a rule of thumb, anything further than twice the baffle width or so is 'far field'. 50cm is far field for most speakers, at least according to the ARTA recommendations. I normally measure around 24" for small speakers to get the furthest room reflections.
That doesn't sound correct.
Got any sources that corroborate a 100Hz limit for spinorama tests?
If this is so, I'd be very interested to learn why.
24" is more than 50cm..
Does it really come as a surprise to you that those curves converge below 100Hz or you are just exepriencing a brain fart?
I don't want to argue which is better, semi-nearfiel fullrange or splitted measurement, but semi in a large hall is for sure easier and fair to see differencies. Soundstage uses them and say that they are unreliable below 80Hz, that's it - we must accept that there is some uncertainty and that we can't get perfect truth. One good point is that it sums port output automatically, but back-ported speakers loose a bit.
Smoothing is not important, raw data is ok for me, I can do smoothing in my head! Good point is that no smoothing shows edge interferences better, in critical 1-5kHz rang - but only in single measurements, not in averaged ones!
I am interested in distortion graphs, they tell me how stressed the drivers are. They can tell about cabinet resonance too. Absolute % numbers are not important. I can live without them, but when listening tests tell something about harshness and coloration, I want to know where xo points are and what slopes and how distortion varies per freq. They also tell how low the bass can blow without a subwoofer. It is easy to show ambient noise level too, just toggle that in REW.
Divided by and scaled in level. Substracting showed some very weird anomalies