Kate asks:
Thanks very much for your helpful article about PA system recommendations. I hope Bose & Sennheiser are kind to you! I upgraded to both recommended items & during testing at home & at a venue it worked perfectly, but once the ceremony started there was some audio issues; couple of those high pitches squeaks and I think a bit of cutting out. It wasn’t a disaster but also wasn’t great, and I’d like my audio to be as good as poss so just trying to figure it out before the next ceremony.
In your experience, do you know what that could have been? Eg more likely to have been a speaker or mic issue? The only thing that changed from sound check to ceremony was that there were more people… can that have an effect? Would massively appreciate any thoughts or tips.
There are two possible sources of the noise, and without hearing it I can’t diagnose it directly.
The first is an easy one, and it’s unique wireless systems, squelch. The other is feedback.
Squelch
Squelch is well described in this Quora article:
Squelch is a function by which the wireless receiver mutes the audio signal when the radio signal drops below a certain threshold. This can happen due to interference from another, stronger radio source, distance from the receiver, or any other situation where some other radio signal (even just background radio hash) is stronger than the radio signal from the desired transmitter. In many cases, these undesired, stronger radio signals may carry louder (or certainly more annoying) audio signals than what would be output from the transmitter, and that is no fun for anyone involved should your receiver suddenly lock to them.
Ideally you set the squelch control so that it is above the level of background radio (noise), but well below the lowest level of useful radio from the intended transmitter (Signal).
So on my Sennheiser G4 wireless receivers look for the Squelch setting in the menu, and I’ve got mine set to High. The instruction manual for my system describes how to change it on page 58 of the manual, but it’s not hard to find and change yourself.
Feedback
When the audio that enters a microphone which is then amplified out a speaker is then received again by the speaker, the frequency bias of that speaker creates an audio loop which you hear as a high pitched sound.
This is a really easy problem to fix.
This is why you’ll see professional audio set ups have the speakers on speaker stands to the left and right of a stage. The audio engineer is physically moving the output of the speakers away from the input of the speakers, the microphones.
An ideal setup would look like this.
Hi Josh, Kate mentioned something about “I think a bit of cutting out”. Would this possibly be because of all the guests that are in between the transmitter and receiver? I read somewhere that RF doesn’t travel well in between people as they contain water. Would this also be true for digital transmission? I’m still tossing up between RF connection and bluetooth connection before making my next big investment in speakers and microphones.
Hi Kim, that’s correct about radio frequencies struggling with water and human bodies which are mostly water.
I had a problem at a rehearsal upon my first time using this system. When I went to switch off the mic prior to switching off the speaker and the receiver, an almighty noise erupted from the speaker from the switch being turned off on the mic. It made a baby cry and I felt terrible! It hasn’t happened again since although I did conduct the first ceremony without turning the mic off until everything else had been shut down, which was not ideal.
Embarrassed to say it also took me a while to realise how to mute the mic :/
Hi Josh, thanks for such a quick reply to my question. Much appreciated!
Happy to say the ceremony went ahead with perfect sound, and my equipment even got a compliment from the acoustic band (“wow, your speaker has such nice sound and volume for its size”). Another thumbs up for your recommendation.
Upon reflection, I’m pretty sure my previous sound issues were due to feedback loop. Now that you’ve pointed it out with those diagrams it seems SO obvious about speaker/mic placement – what can I say, except total rookie error 😛
Clearly, public speaker comes more naturally to me than tech skills but I’m learning. I know it’s super important to be very familiar with my equipment but until this problem came up, I didn’t even know what I didn’t know.