Concerned About New Amp

[John Mulcahy]

Weird! What the heck is going on in my room (or with my computer)!?!

Was your plot made in Spectrum mode or RTA mode?

 

[John Mulcahy]

Here's another pic and MDAT. I just repeatedly measured the same speaker.

Four of those measurements show a lot of low frequency background noise. Traffic can cause that, for example.

 

[thothsong]

Was your plot made in Spectrum mode or RTA mode?

Is there a smoothing function that would make RTA mode that smooth below 40 Hz? And the high SPL above 20 kHz seems very strange.

 

[tjcinnamon]

Four of those measurements show a lot of low frequency background noise. Traffic can cause that, for example.

View attachment 62851

Hmmm. I’ll have to remeasure. I think I had my DIY subs turned off. Those can create noise. But if it’s only a few measurements, it’s certainly outside the scope of something perpetually running in the background

 

[tjcinnamon]

Was your plot made in Spectrum mode or RTA mode?

I’m not sure. I hit the RTA button. Is spectrum a sweep?

 

[tjcinnamon]

As @sam_adams indicated, there's usually less than 30 dB separation between your measured SPL levels and your noise floor, and sometimes barely 20 dB, which presumably causes the RT60 calculations to go large, as there isn't sufficient decay over time before hitting the noise floor. If your RTA measurement was somehow just a fluke, then as suggested the fix is to run the sweeps at a sufficiently high SPL.

Someone else (in addition to you) pointed out that low SPL measurement can cause anomalies that look like my results in the RT60 graph

 

[thothsong]

I hit the RTA button. Is spectrum a sweep?

While the RTA window is open, click the gear icon in the upper right (graph controls), and look at what Mode is set to.

 

[tjcinnamon]

Four of those measurements show a lot of low frequency background noise. Traffic can cause that, for example.

View attachment 62851

Someone else (in addition to you) pointed out that low SPL measurement can cause anomalies that look like my results in the RT60 graph

John, do you believe that to be true as well?

 

[John Mulcahy]

RT60 is a measure of the rate of decay of the filtered impulse response. If the noise floor is very high there may not be sufficient decay to get a good RT60 estimate. Aside from areas affected by background noises your measurements are OK, however. The latest (ea68) build should give you cleaner RT60 results, but more signal level would help. 60 dB is quite a low level if you are not in a very quiet environment.

 

[tjcinnamon]

RT60 is a measure of the rate of decay of the filtered impulse response. If the noise floor is very high there may not be sufficient decay to get a good RT60 estimate. Aside from areas affected by background noises your measurements are OK, however. The latest (ea68) build should give you cleaner RT60 results, but more signal level would help. 60 dB is quite a low level if you are not in a very quiet environment.

much appreciated. I'll be cognizant of external noise. I'm pretty surprised because my room is pretty damped with treatments, double 3/4" drywall, and green glue. That said, it's not decoupled from the ceiling and there's ducting.

I'll be sure to get the latest build. I have "include beta updates" turned on.