On 16/02/2025 at 12:32 PM, Satanica said:

50Hz ground loop with No AVAA C214? It doesn't seem to appear With AVAA C214. Perhaps some components were move around on power outlets comparing before and after.

Hi Satanica,

 

Thanks for taking the time to look into the measurements and share your thoughts. I totally get where you’re coming from with the 50Hz ground loop idea.

In my experience, though, I don’t think it’s a 50Hz cycle. Here’s why:

The before-and-after measurements with the AVAA units were done just a few seconds apart, and no hum was picked up during that time. The color of the flame indicates that it would have been quite audible in such a quiet environment.

Resonance Patterns: I’ve come across similar resonances in many rooms, especially ones with multi-sub setups. The patterns usually come from room modes rather than electrical interference.

I’ve attached a couple of examples from a similar room, this project was posted as  "Wongaburra - El Tel's Listening Space", where you can see how the resonances shift depending on the speaker and listening positions.

Hope this helps make sense of what we’re seeing here. AVAAs work extremely well in these scenarios.

Kind regards 

19 minutes ago, CORSINI Acoustic Solutions said:

Hi Satanica,

 

Thanks for taking the time to look into the measurements and share your thoughts. I totally get where you’re coming from with the 50Hz ground loop idea.

In my experience, though, I don’t think it’s a 50Hz cycle. Here’s why:

The before-and-after measurements with the AVAA units were done just a few seconds apart, and no hum was picked up during that time. The color of the flame indicates that it would have been quite audible in such a quiet environment.

Resonance Patterns: I’ve come across similar resonances in many rooms, especially ones with multi-sub setups. The patterns usually come from room modes rather than electrical interference.

I’ve attached a couple of examples from a similar room, this project was posted as  "Wongaburra - El Tel's Listening Space", where you can see how the resonances shift depending on the speaker and listening positions.

Hope this helps make sense of what we’re seeing here. AVAAs work extremely well in these scenarios.

Kind regards 

Hi, I'm struggling to make sense of this. I think there is some electrical issue here. Sound decay should look much more natural. This here appears to be continuous energy up to 1000 milliseconds with no sign of decay! And I'm especially suspicious because in two different setups and two rooms the main issue is exactly on 50Hz. As I mentioned previously, I've had this kind of issue myself. It showed up on the spectrogram plot precisely as this, but it was not audible until I played music where it presumably added to the signal. How did I resolve it? I unplugged an offending rear subwoofer from one outlet and put it into another and the issue was completely resolved.

Further to this, I presume that both screen shots are in Fourier mode. Referring to this attachment is an idealised Fourier mode example. In your two screen shots above, at 50Hz there is the same amount of energy at -200ms at 1000ms which looks like continuous energy. I could be wrong, but I interpret -200ms to actually be time zero and there is already "this" energy there.

13 hours ago, Satanica said:

Further to this, I presume that both screen shots are in Fourier mode. Referring to this attachment is an idealised Fourier mode example. In your two screen shots above, at 50Hz there is the same amount of energy at -200ms at 1000ms which looks like continuous energy. I could be wrong, but I interpret -200ms to actually be time zero and there is already "this" energy there.

Thanks for the feedback. After looking into it more, I realize I misinterpreted the spectrogram and likely mistook a 50Hz hum for room modes. The unvarying signal at 50Hz was also accompanied by harmonics at multiples of 50Hz. Appreciate the insights—definitely a learning moment for me!