Super low hum/buzz from subwoofer

Hi all,

Just to get my sanity check here because it may be just me being paranoid about the sound from my subwoofer.

My Hsu VTF-2 MK5 is about 1.5 month old, the sound is amazing, but I recently notice that when the sub is on and idle, there is faint noise coming out from it. Here is the videos if you want to listen to: https://drive.google.com/drive/folders/1vzEAQ6oLhkm3b-UV_Z3CszSEc387iMpD?usp=drive_link

The noise coming out of it is so low that you have to put your ear next to the driver to hear it. However, it is more noticeable even from my MLP during the quiet time. I tested with and without the sub cable plugged in:

• With no RCA plugged in, the noise is still there, but significantly faint, definitely not dead silent
• With RCA plugged in (and it does not matter whether my AVR is on or off), the noise is definitely there, and louder than without RCA in. You definitely can hear it in my video.
• In both cases, raising the volume knob will increase the noise
• Another issue is there is a pop when I cut off the power from the smart switch (I use a smart switch to turn on the sub via Home Assistant instead of the auto on/off function on the sub), but my guess is it is just an in-rush voltage when it's on? Correct me here if I am wrong.

I have ruled out:

• Ground loop (because the AVR and the sub are on the same Tripplite isobar. And I also switched the sub to another outlet, with a different cable extension)
• Problem from upstream equipment (because in the same setup, my previous Polk XT10 is dead silent on idle, and I use Mediabridge and SVS cable, which I believe are high quality)

I read somewhere on AVS forum, and I think someone had a similar issue, and the suggestion is to flip the cross-over in the back of the sub to "in" and set it to 90Hz. Now, this DOES cut off a significant amount of noise, but does not eliminate it completely. And combining this with the smart switch trigger, the sub pops when the power is applied ( but not when cross-over is set to "out", weird). So it is not a viable solution.

Am I insane and too sensitive to this noise?

On top of this issue, the sub seems to have a cosmetic defect that I just discover as well.

I have been trying to contact Hsu support for like a week, but they are painfully slow. I sent 2-3 emails to their tech support email, and no reply yet. I also gave them 3 calls, and one of which a person returned my call later, requesting the recorded videos, and I did. But that is it, I haven't been able to talk to anyone since then. I understand they are small company, but man....this is driving me crazy...

Any tip guys?