Diy Rta

[CoolCat]

here's a basic Allen Heath/RTA/NAdy measurement mic read in a 11x13x8H HR room. Ysm1p and "jbl sub" and Pink noise. Chart is from the mix seat position.
it appears to be +/- 4 db except at the extremes.

the hi-end sure dropped off as the 100hz and below volume came up?
any explanations for this?

 

[Ethan Winer]

> the hi-end sure dropped off <

How flat is the microphone? Did it come with a custom calibration curve? I'm sure your speakers are not so flat way up there either. Even if the mike and speakers are each rated flat +/- 3 dB up to 20 KHz, together that's a 6 dB drop. Also...

> it appears to be +/- 4 db except at the extremes. <

If only. Third-octave RTA measuring is woefully inadequate for assessing the low frequency response in a room. You need more like 1/24 octave or even finer. The graph below shows the exact same test results displayed as both 1/3 and 1/12 octave at the same time. You can see that the 1/12 octave graph shows the true extent of the peaks and nulls much better than the 1/3 octave version. But even the 1/12 octave graph hides much of the real detail.

--Ethan

 

[CoolCat]

thanks again Ethan.
I called Allen Heath and never got it straight on the 1/12 and 1/24th. My misunderstanding was A/H was 1/24th....
thanks for clarifying its a 1/3rd octave.

I do understand the resolution showing more dips and spikes, but thats cool.
If it looks worse under higher resolution thats alright with me.

the 1/24th really magnifys the movement of things I'd imagine, like the traps, speaker angles, mic positions.


I hope to get a old small laptop and a software someday to do this. lugging an old pc and CRT monitor around is a dog.