My tests were done a couple of years ago and as technology advances the situation could have improved. I used a system from Sennheisser as well as infra-rot, bluetooth and FM, I found nothing at that time useful but then it was also not a major direct goal it was primarily for artist cue - but even for that the quality was too poor near the audible extremes with poorly or perhaps un-handled rolloff (i.e. trying to push the F-response beyond it’s limits).
All this is relatively unimportant however as I said technology advances (however usually in the consumer market which favours compressed MP3). This is why I recommend the most important thing to do is test your system (you’ve bought it) for critical listening, frequency bandwidth, volume levels, balance, crosstalk, latency - the whole works fully uncompressed. By all means use your ears but try and incorporate a software analysis program such as the free but very powerful REW (Room EQ Wizard).
My assumption was you were asking about their use in a “critical listening” setup. In this case, it’s not the same as a speaker which doesn’t have good bass response, the situation would be speakers that have a wider FR than the transmission system, and they will highlight any ragged edges so to speak.
Awesome, thank you so much, BriHar, thanks for sharing your extensive experience 
!
As a relative newbie, I still had a conceptual question, as in the 2nd part of my last post - am I misunderstanding by thinking for the purposes of testing the mix out for “portability” on a non-studio system … listening to the mix via FM transmission on consumer speakers is akin to listening to the mix on car speakers, iPod earbuds, or Auratones - absolutely there is signal degradation, but that’s OK for the purpose of testing in different environments?
Thanks much for any further thoughts!
Certainly, for the purposes of translation (what you refer to as portability) this is a valid environment.
As they say “just do it!” and if there are any issues you’ll have to address these then, i.e. determine if they are caused by the transmission, propagation artifacts or whatever. It could still also mean that you’ll need a compressor on the transmission side, by try first and see (or hear).
Thank you again, BriHar, so wonderful that you share your extensive exerience 
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