FFT size in SpeakerWorkshop

[jm_kzo]

Dear all DIYers,
I am having my first attempts at SpeakerWorkshop and it all went well when doing impedance measurement but I am now scratching my head about "accuracy" of the frequency response measurement or more specifically what is called elsewhere "the size of the FFT" (as a number of points)

By default frequency response graphs are displayed with 256 points (in graphic properties).

Is it meaning that it is a 256 points FFT ?

Then you can change this and make it display 1024 or 2048 points (possibly more).
When you change this, is it meaning that the size of the FFT changes from 1024 or 2048 points ?

If I do have it all wrong, can someone please tell me how you can set teh FFT size in SW as I have been around all preferences screen and I have yet to find something close to "FFT size".

Many thanks in advance.

[claudio]

Hi,
Speaker Workshop limits the resolution of the data looking at the sample rate and the time gate, limiting to 128 points up to a time slice of 9 ms (for a 48k sampling rate), then goes to 256, 512, 1024 with approximately each doubling of the time window; the only way to increase the number of data points is to increase the length of the gated measurement or, to some degree, increasing the sample rate. So it helps to move the first marker close to 0, as well as to increase the latency. You can check the number of data points (resolution) by right clicking in the response chart and choosing PROPERTIES, then go to the SPECIFICS tab. You can change this number and the graph will look slightly better for crossover modeling, but once you repeat a measurement SW will reset this number according to its algorithm. Do some tests moving the markers to have an idea of how it works.

[jm_kzo]

Thanks Claudio, I will try this as soon as I can (most probably this week-end now).