FSAF (Fast subband adaptive filtering) measurement

[FSAF]

Interesting. I do not understand why ESS TD+N (~15 dB SPL) are so different from FSAF TD+N (~52 dB SPL) which are mostly noise. BTW, which 6" midrange driver?

 

[dcibel]

Driver is a B&W FST.

ESS is able to resolve a much lower noise floor than FSAF. I highlighted previously, my own measurement below. Top traces are FSAF noise floor, bottom are sine sweep.

I do agree that @Tikkidy should have been able to achieve much better than 50dBSPL noise floor in his FSAF measurements.

 

[FSAF]

I am confused. Maybe we are talking about different things using the same words. Did you try using pink noise (with the same power density and duration as ESS) as the FSAF stimulus and compare "apples-to-apples"?

 

[dcibel]

It's been a while since I took these measurements, I checked and the FSAF measurement used a 15s music clip, however I believe this fact should be irrelevant for the comparison above. The comparison is from REW noise floor determination, which is the 2 second recording prior to the measurement occurring, so the noise floor is the noise floor regardless of stimulus. IIRC REW employs some variable windowing tricks to lower the noise level in a sine sweep measurement, I'm sure John can provide more detail on what differences exist.

 

[John Mulcahy]

I'm sure John can provide more detail on what differences exist

The sweep noise floor plot takes into account the process gain applicable to the sweep length so that the noise floor plot can meaningfully show where distortion rises above the noise.

 

[Tikkidy]

Yes, it's a puzzle to me as well. In fact, when I first sent these to @FSAF with +36dB gain applied, there was so much noise, we could not reconcile what the problem was.

Another session testing, this time at day break.

This time Sweep 1M samples, no repetitions, no SPL normalization for mic distance.
vs Pink Noise, various IR lengths, various mic selector

This is the midrange from the B&W 801D4 (2022 release)