How do you control the rate of sampling/averaging when measuring frequency response

[Socket]

I am sure there is a simple answer to this, but I have been measuring the frequency response of my speakers using REWs RTA function
For as long as I have been using REW, I would over about 30 seconds of measurement get an average of 50-60
Today over 30 seconds of measurement I am getting 200-220 the averages, the RTA graph stablisers so quickly under these conditions that I cannot complete a full sample
Is there a setting to control the speed of sampling or the number of averages taken when using the RTA

For reference the settings are:
Mode: RTA 1/24
Smoothing: No smoothing
FFT length: 64K
Averages: Forever
Window: rectangular
Max overlap: 93.75%
Update Interval 1

Thanking you in advance

 

[John Mulcahy]

Are you using a higher sample rate? If nothing else has changed that would increase the update rate. The FFT will update when enough samples have been received to meet the allowed overlap. For example, if the overlap is set to 50% the FFT will not update until half the FFT length samples have been received (32k samples for your 64k FFT). If the overlap is 75% it will update after a quarter of the FFT length samples (16k samples). Using a lower overlap will slow the update rate, but the time it takes the number of samples required to be received depends on the FFT length and the sample rate. For example, at 48 kHz sample rate (48,000 samples per second) it takes 16384/48000 seconds to receive 16k samples, 341 ms. At 96 kHz sample rate it takes half that time.

It is also possible to update the graph less often, the Update interval controls that. If the update interval is 4, for example, the processing is carried out per the settings but the results are only drawn to the screen every 4th time. Normally only used if the system has very limited graphics capability.

 

[Socket]

Are you using a higher sample rate? If nothing else has changed that would increase the update rate. The FFT will update when enough samples have been received to meet the allowed overlap. For example, if the overlap is set to 50% the FFT will not update until half the FFT length samples have been received (32k samples for your 64k FFT). If the overlap is 75% it will update after a quarter of the FFT length samples (16k samples). Using a lower overlap will slow the update rate, but the time it takes the number of samples required to be received depends on the FFT length and the sample rate. For example, at 48 kHz sample rate (48,000 samples per second) it takes 16384/48000 seconds to receive 16k samples, 341 ms. At 96 kHz sample rate it takes half that time.

It is also possible to update the graph less often, the Update interval controls that. If the update interval is 4, for example, the processing is carried out per the settings but the results are only drawn to the screen every 4th time. Normally only used if the system has very limited graphics capability.

Understood, thanks so much John, Ill think it might be the overlap, ill play with the sample rate and overlap to see if that makes a difference. Thanks again

 

[Socket]

Yes I can confirm turning down the overlap to 50% did the trick.... thanks John