Why might these high frequencies appear to null in REW?

[1niltothe]

I have put together a temporary setup in a large untreated room. Despite the very uneven response, it has certain advantages for music production, compared to my treated studio.

I ran a REW measurement mostly out of curiosity. The low end came as no surprise, but I feel less confident with the high end.

What do you think might be causing these weird fluctuations? Are they nulls, or is it that there are peaks at the lower end?

 

[raindance]

You need to measure one speaker at a time or comb filtering effects will cause periodic cancelation.

 

[GXAlan]

If you are measuring in stereo, it is the nulls. Scroll down to the simulations here

 

[1niltothe]

Thank you. I took L and R separately and indeed the higher frequencies measure more evenly. I also added a subwoofer and moved things round a little bit.

It looks now like some room modes are creating peaks lower down, apart from that not too bad to be honest. I'm not very experienced with this stuff so probably overlooking very obvious things.

Here's the graph of separate L and R with smoothing anyway.

 

[GXAlan]

What’s great about measurements is that you can try toe-in and toe-out to see how the measurements work both in mono and stereo.

 

[raindance]

Thank you. I took L and R separately and indeed the higher frequencies measure more evenly. I also added a subwoofer and moved things round a little bit.

It looks now like some room modes are creating peaks lower down, apart from that not too bad to be honest. I'm not very experienced with this stuff so probably overlooking very obvious things.

Here's the graph of separate L and R with smoothing anyway.

View attachment 316377

Are you measuring from the main listening position? That high freq rise makes me think you're quite close to the speakers, or maybe they have a lot of high frequency boost, which is fairly unusual. In most rooms from the usual listening position 8' or more away from the speakers you'd expect a gentle downward slope.

 

[ozzy9832001]

I have put together a temporary setup in a large untreated room. Despite the very uneven response, it has certain advantages for music production, compared to my treated studio.

I ran a REW measurement mostly out of curiosity. The low end came as no surprise, but I feel less confident with the high end.

What do you think might be causing these weird fluctuations? Are they nulls, or is it that there are peaks at the lower end?

View attachment 316314

As raindance said, you can get comb filtering from the 2 speakers when played together if the tweeters aren't exactly aligned during the measurement (meaning one speaker or the microphone is as little as a half inch off can throw it off). Also, if a chair is present that can cause it as well.