Well, I did not purchased my units from Massdrop. Instead, I bought mine in China directly from Swan. The radio interference issue happens to me all the time. Swan does not confirm they have flaws in the design (that might not be for all the model line, might just for the production line in certain time period).
I have seen that the importer in the North America also said there is no official awareness of the design flaw. I have changed my living space twice in the U.S., and the problem was not resolved by all means. I have upgraded my RCA cable twice, from a normal 15 dollars cable to the "Blue Jeans Cable" which is, to my point of view, the high-end cable (at least for this speaker unit). I have also bought bunch of ferrite core to cover the wire, and nothing changed significantly. There is still noise coming from the speakers even there is no input connected.
Surprisingly, I have read through most comments section under the Chinese seller site, and I didn't see any post mentioned the interference (I did not gone through all comments, but I haven't seen any in about 20 pages). For a second, I thought that might be the input voltage problem (in China it is 220V), so I bought a voltage converter. Unfortunately, the problem still exists after this. The noise is annoying, and what more disappointing is that I spend money on something that is supposed to be better that Edifier, but it failed badly. The noise just like the itch from your back where your hands can't get it.
I have contacted with Swan recently, and they acknowledged that this issue might be result from a production defect. Since I will go to China this Winter, I will give a shot. Maybe also try to open the woofer and speakers to figure out the shielding inside. If possible, I want to upgrade the RCA cables connected to the speakers. Those looks like really poor quality cables anyway.
If all these won't help to minimize the noise, I might just send these pair to my friends as a gift. Right now, I can't even leave my speakers on for one extra second without the music is on. What more horrible is that sometimes my main volume is not that high, and the noise will mixed with what ever the sound comes from the media file that I am playing.
Meanwhile, I highly recommend Massdrop renovate their website, so people could search comments by keywords. That will help people to know what happens to previous buyers. Besides, they really should warn buyers about known possible defects of the product listed. To me, they are pretty much ignorant on such issue.
Once the problem is fixed (I hope it will be), I will post update here.