After investigation, the woofers in my 3-way time aligned system were offset by a few samples relative to the mids and highs. Fixing that plus linearizing the drivers led to a better response:
it's something like thisThanks for the link. Now that you mention it I seem to recall Geddes posted a chart showing gamma-tone impulses and their duration not too long ago.
Thanks for the links.Geddes said he calculated the gammatone filter at 70hz to be about 60ms and 50ms at 100hz. If we were to go by these numbers then it seems a variable fdw would be necessary.
It is not my intention to start an argument, just food for thought......what window length vs. frequency best corresponds with the way we perceive sound in a room? REW seems to default to 15 cycles, is there anything behind that number to explain the choice there...
It's clear to me that highly trained listeners can "hear" things that the average Joe can't, but I'm not so sure that's outside of the current understanding of how we hear. There seems to be a lot of grey area in psychoacoustics and it seems much of that is interpreted differently by many. I seek to find the interpretation that correlates objective data with my subjective impression......when these things jive I feel I'm on the right track.It is not my intention to start an argument, just food for thought...
I am thoroughly convinced that, although the "norms" given from the research are certainly "normal" and accurate and therefore useful in understanding a baseline, that some of these perceptual patterns are subject to exposure and experience, and can be trained to discriminate with finer resolution well into the areas where they are thought not to be able to. This does no mean that such an individual is exceptional or weird or is "wired funny," only that he has paid attention and learned to hear things outside the norm. FWIW.
Here is MP exported reimported 15 cyclesSome measurements of my L speaker (which is a fairly small sealed speaker, MK MP150). Mic is at the usual MLP about 3m away, mic pre is an RME FireFace 800, mic is a CSL calibrated EMM6, same levels used for both sweeps & same length sweeps used (approximately... 512k in REW is 10.9s and it was a 10s long sweep in Acourate) & same freq range (10-24000Hz).
Two wavs attached, one is the acourate sweep itself (in 24 bit PCM form for import into REW) and the other is the same after a 15 cycle FDW applied.
Comparison of REW variable smoothing and acourate 15 cycle FDW below
View attachment 94442
and the same for this oneOK, here we go. It appears that the "default" psychoacoustic smoothing in Acourate works this way: The window width is a linear interpolation from a low frequency of 16 Hz up to Nyquist. Not sure why Nyquist, but if the Sample rate (most commonly used) is 48 kHz that would be 24 kHz, which isn't too bad as a standard.
He takes this window measure on 1/24th octave intervals.
The apparent "default" window width is specified as 15/15, which means 15 cycles at the low frequency and 15 cycles at the high frequency. These values can be changed, but I've found they produce a result that correlates well with the ear's interpretation of the response. 15 cycles would be 15 ms. at 1 kHz. To the best of what I can determine this is actually the right hand window width, and he uses a Blackman, but some experimentation is in order. Anyway, changing the left hand window size, as long as it is reasonable, does not seem to affect the displayed frequency response.
To compare REW and Acourate I took a screenshot of Acourate's psychoacoustic response of my front left speaker taken at 9 feet distance. I exported the impulse response as a 24 bit/48 khz wav (attached). I then used my usual 500 ms. Tukey with 1/6 octave smoothing to display it in REW. I then saved this as a PNG. I then brought both of these into photoshop, carefully matched the scales, extracted the Acourate curve with the magic wand tool, and overlaid them matching amplitude at 1 kHz. That's the image I've attached.
I'll give you my thoughts about these differences in my next post in this thread.