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Old 23rd February 2021 | Show parent
  #20
Quote:
Originally Posted by afroblue ➡️

Back to the measurement from 140cm

I don't understand how to interpret impulse response measurements.

Basically early reflections from 0-20ms you want all reflections to be surppresed -10db(ITU-R BS.1116-1), -20db(more suggested) or -30db(ideal Blackbird Studio C ). The ETC curve leans more to hi frequency content and the reflections that will cause nulls and peaks in frequency response.

You can also filter the response from 1khz-10khz specifically to a selected frequency(1/3rd octave) to narrow down where the reflections are coming from.
(look at attachment for 1khz reflections).


Quote:
Originally Posted by afroblue ➡️
RT60 Topt. This is how long it takes for a frequency to drop 60db?

so looking at ETD line, 50 Hz is lingering too long -up to 750ms - in fact that whole low end is hanging about. yes?

Is the Topt line where I'm aiming to get the ETD to be? Again, how do I do this?

This is a steep learning curve for sure!
From the manual on Topt(I suggest you read manual by the way as there is a lot of great information):

An "optimal" decay time based on the slope of the Schroeder curve over a variable range chosen to yield the best linear fit. If the early decay time is much shorter than T30 the Topt measure uses a start point based on the intersection of the EDT and T30 lines, otherwise it uses -5 dB. REW tests every end point in 1dB steps to the end of the Schroeder curve and chooses the one which gives the best linear fit.

So when looking at the Topt curve from 1khz-10khz ideally you want a consistent straight line with no deviations. From 200-4khz if you are trying to tune room to the ITU-R BS.1116-1 standard you don't want any deviations more than +/- 0.05sec.
Attached Thumbnails
REW graph analysis (spl,waterfall,etc,rt60)-screen-shot-2021-02-22-8.15.38-pm.jpg   REW graph analysis (spl,waterfall,etc,rt60)-screen-shot-2021-02-22-8.15.29-pm.jpg   REW graph analysis (spl,waterfall,etc,rt60)-screen-shot-2021-02-22-8.24.53-pm.jpg   REW graph analysis (spl,waterfall,etc,rt60)-screen-shot-2021-02-22-8.25.21-pm.jpg   REW graph analysis (spl,waterfall,etc,rt60)-screen-shot-2021-02-22-8.36.23-pm.jpg  

REW graph analysis (spl,waterfall,etc,rt60)-screen-shot-2021-02-22-8.36.30-pm.jpg   REW graph analysis (spl,waterfall,etc,rt60)-screen-shot-2021-02-22-8.36.50-pm.jpg   REW graph analysis (spl,waterfall,etc,rt60)-screen-shot-2021-02-22-8.37.00-pm.jpg  

Last edited by thethrillfactor; 23rd February 2021 at 03:03 AM..