I seem to have the same issue, I just sent Thomann (Germany) back a new pair of iLoud MTM for replacement.
Both made a very annoying whining sound when powered up. The sound consists mostly of 2.7 to 3kHz, with peak around 2.9kHz, also some higher frequency components are there.
The sound originates somewhere back side of the speaker, and it is similar how for example cheap USB-chargers whine. So, I conclude that this is a power supply problem; a noisy coil etc..
It is a very annoying and fatiguing sound/noise, here is a recording of it:
https://www.dropbox.com/s/rc50fqnp3hcpq ... 7.mp3?dl=0The recording was made with cardioid-pattern mic at approximately 15cm from the back of the speaker.
Except for this issue I was really really happy with the initial (one-day) experience of these monitors, especially for the low end, and how good they perform after calibration in a non-optimal room. I am going to use these in a location that cannot be optimised for acoustics. In my other, acoustically treated space, I have had Adam A5X:s with subwoofer for years.
I am a bit worried that the replacement iLoud MTMs will have the same problem... But I hope for the best.