IEM Question

[rob aylestone]

If you (think) say so.

I know so - when I first finished my education, I was going to be a radio engineer. If you have a guitar transmitter then the field strength from your back pocket to your skin, and worst case, your brain is so low with the maximum permissible output level, my equipment struggles to measure it. A walkie-talkie in the pocket would be 100 times the output power, and even that is not considered a risk. A mobile to your ear would be much, much stronger in field strength, and despite repeated scientific tests, there appears to be no evidence of any health considerations. Clearly, the science says there is RF energy of a measurable amount, but even at cellular phone frequencies it is not known to cause any biological cell degredation. Of course, it could, but so far, none has been evidenced. Sticking IEMs in your ears has one potential health issue - volume. However, most IEM users actually don't have them very loud.

Bluetooth headphones are extremely low powered, short range, so those that do actually transmit have not only minimal field strength, the duty cycle (time transmitting vs not transmitting) is extremnely low too. In fact, transmitters on stage and studio can cause interference by getting into the system on cabling - but while you occasionally get the nasty motor boat noise from a phone doing it's high power polling, radio mics and transmitter packs just don't do this.

The web would have us all believing that everyone microwaves their brains from tiny button cell devices, but there is no evidence whatsoever that this is anything real? I'm not on a cause or anything, but if you are a typical musician on stage every night, the most common medical conditions or episodes seem to be, in order of seriousness:
1. Electrocution/electric shock - faulty or incorrect use of equipment
2. Hearing - we ALL know somebody who has serious or just partial hearing impairment
3. Falls and Slips - I found a few studies but trips seem the most common, and a few drum riser falls, and of course stage edge.
4. Strains and Sprains - mainly loading and unloading
5. Cuts and bruises - another obvious, but relatively minor injury area
6. Laser damage to eyes - Difficult to quantify, but a few evidenced incidents with improper use of lasers
7. crush injuries - just a few, but occasionally serious.

I found others pyrotechnics, even working with animals, but I could not find ANY recorded incident to do with RF Energy.

Of course, everyone is entitled to believe anything nowadays, but while that's OK for individuals to believe, I don't think it can be promoted without evidence to others? Believing something do not make it exist.

Soapbox mode off - sorry.

 

[bouldersoundguy]

Short version of above: Other than radio waves strong enough and of the right wavelength to cause a thermal effect, they have not been show to have any detrimental effect.

 

[rob aylestone]

To put this into some kind of perspective - with today being a litigeous society, you will now find warnings applied to RF products, even the Chinese ones when they are needed. At radio sites, not just the mega power broadcasting ones, it is common to find the access to the ladders restricted. Some so restricted that with power to the transmitter racks applied, the key is interlocked so you can only climb isolated masts. With cellular radio the most common source, exposure to the antennas, by proximity has to be restricted as Bouldersound mentioned above - they are in essence microwave ovens. People have sort of slid this science to mean that any RF source is dangerous, or at least a risk. If you want to read more, google ionising and non-ionising radiation. It's well understood.

We must manage risk, but here, there seems no risk we can actually detect.

Going back to the IEM thing - one thing nobody has mentioned is stereo. IEMs are very rarely two totally separate channels. Being able to shift multiple sources left to right really helps - in the band I had me and my bass 75% right and everyone else 75% left - this helped me hear myself much better. It is also an area that never gets mentioned in reviews. Many of the cheaper Chinese IEM products are actually mono! The receivers do not have stereo at all. The proper stereo ones, Sennheiser, in my case use a very similar system to FM stereo, but it doesn't produce two separate streams, it's done by a sum and difference technique - a bit like how we do M/S. So the main signal is mono, and the extra channel pulls some of the stream left and the other right. It's done using a system called multiplex - two signals stacked one above the other. The downside is that if you send something 100% left, it leaks a bit into the right. Not much, so most don't even notice. The chinese ones have left/right and mono inputs, but all the ones I have had just seem to merge left and right and as far as I can tell, are just mono. Nobody has actually mentioned this that I've seen. The Chinese receivers (I have a few left over) do NOT decode a proper stereo IEM signal. You get a fine mono signal, but they are not stereo. Funny how nobody ever mentions this. I've had three systems from China, spread out over two years and all were mono.

While we're talking about IEMs we should also remember that wireless in general is unreliable. The best wireless system is nearky as good as a $10 cable. Signal strength is the thing we all talk about, but really the problem are the common, unpredictable RF black holes. You take a step forward and a perfect signal just vanishes. RF systems in the same band can suffer from desensitisation - a transmitter pack in your pocket makes the receiver in another pocket, deaf. I had this with my bass. A sennheiser pack taped to the strap. My IEM receiver in my pocket. It just made the black holes a bit worse, and if your IEM cuts out, you are stuffed. I swapped to a line 6 system for my bass, which was much more reliable and didn't upset the IEM. Actually a great system, but a rubbish battery compartment clip, which needed copious gaffer tape to keep closed.

 

[bouldersoundguy]

I strongly agree about stereo. It's especially critical for vocals, but helpful with guitars and pretty much everything. I have a cheap Audio2000s IEM setup. It's actually analog, which is unusual these days, but it is stereo. The range is limited, but it sounds good and the stereo makes it especially effective.

For any musician who sits in one place, there's not a real good reason not to use a wired IEM. It's way more reliable and much cheaper. I know people who move around using a wired IEM attached to their instrument cable.