Recent content by jan.didden

In fact, I am simulating a clean acoustical source by using two small speakers, each emitting a different tone. (I have two instances of REW running). Since the two tones do not intermodulate in the air, any intermodulation distortion is from the mike alone. I note the level and phase of one IM...

There are no 'mic with lower distortion'. Nobody specifies their mics at say 90dB SPL. All specs read like '<3% distortion at 148dB SPL'. I've been measuring 6 mics so far, from vintage 1/2 inch B&K to 1/4 inch modern high power electret touted as 'very low distortion'. They vary very little at...

That is quite impressive! I am trying to wrap my head around the phrase 'make an RTA measurement of the system measuring itself'- which I guess is a loop-back. In my case I want to measure a clean acoustic source with a microphone, null out the microphone distortion using this technique, and...

John, OK, I do that, then cycle the gen on and off to load the new settings, then run the RTA again. But the difference at the 2nd harm freq is minor, a few 10th of a dB, the phase flips from -62 to +125. I'm missing something. Jan

The REW generator can be pre-distorted with settings in the Distortion Controls window. I want to use this to try to null out a specific harmonic frequency in a measured spectrum. I import the actual measured harmonics from the RTA in the Distortion Contols window with 'Set from RTA'. That works...

John, thanks for that overview. My use of the .wav is to import it into Excel for further processing, like manipulating individual frequency components and do some goal seeking. Jan

Apparently there is some interaction between instances. If I open REW from scratch I do get the save action, showing the saved files panel to the left of the RTA window. If I right click the graph I get the option Generate min phase|Generate but that saves the ,mdat, not the .wav. Is there a...

Keith that would be great, but when I right-click in the RTA window the message I get is 'No action'... What I do: I open two instances of REW, and set each Generator to a different frequency to a different channel. That way I get a 2-tone IM signal. I switch on both generators. I open RTA in...

John, I assume you refer to the 'Current' button with the disk icon. When I click that, nothing happens as far as I can see. BTW Spawning two instances of REW and use each to emit a different tone to a different channel does work to generate a two-tone IM so thanks for that solution! Jan

Made progress to my goal of measuring microphone distortion. But some of REW's bookkeeping eludes me still. I am doing an RTA, then I want to save that measurement as a .wav file. The Help says Alt-O should convert current display into measurement, but there's no action when I press Alt-O. I...

@Keith_W - yes that should work! I'm still struggling with the bookkeeping, selecting a folder to save results seems to block anything but the top folder. But I know how to complete the process. Jan

Hi John, see my previous post please. My question: would it be possible to allow the user to enter a signed integer or fraction in one of the slots of the Trace arithmetic....? Jan

OK, some progress. I found out that you can save a current measurement and it appears as a tile in a list next to the RTA window. I name it origA. Then I move origA in both the A and the B slot in the Trace Arithmetic and calculate A*B, which gives me origA^2, named origSquared.. Next I need to...

Well, normally you would take a clean source, measure that sound with a mic and see what distortion that mic adds.. The problem is that 'a clean source' has more distortion than the mic you want to measure so that's a dead end. The method I use (which has been used, on and off, for decades) is...

@Keith_W, I have that paper as well. There doesn't seem to be any real data in it. Microphone distortion numers are rare as hen's teeth - the best you can hope for is like "<2% at 160dB" or similar. (My end goal is to measure the distortion of my electrostatic speakers down to -100dB). I believe...