falcon said:
We have rented 5
Audio-Technica 600 series wireless
headset mics. We have 4 of them working perfectly, but the 5th one is causing us problems. It's jumping recievers, causing
feedback, there is tons of interferance on the
line and so forth. Any basic problem that you can encouter with them, it probably has done that. Now, thes mics work on the the 400 mhz frequencies and for anyone who knows waht they are, they are all A band frequencies. Each reciever/transmitter can be set to one of ten channels and we've tried them all, excluding the ones that the other 4 mics are on, of course. Does anyone have any ideas as to what can be going on, or did we just get a really crappy mic mixed in with the good ones?
On another note, I have 6 other wireless mics (I can't remember the brand, but I think we got them from Rockford...) that we have hooked up to compressors and sometimes, the mics don't work, but it works when I remove the
compressor from the
channel. How do I make it work with the
compressor? and if anyone can give me the basic of how compressors work and how to use them properly, let me know.
Hiya falcon,
Couple things to check with your AT--first off on the
Audio Technica 600's, its a NON DIVERSITY
system. It may have two antenna's but its not a diversity
system (and you can check with AT on the website for that too)..so its very suceptible to frequency interferences. Second--its a lowband UHF--also suceptible to problems. Since you have gone the route of changing frequencies and still have probs, my best guess without seeing it is that the reciever or transmitter is having frequency issues that are not locking. So--the way to see which it is, is to assign a different
beltpack to that problem reciever, and then assign the problem
beltpack to a different reciever etc--see if the problem carries to another
unit or
beltpack you know works fine. That narrows it down... If it carries to another reciver--then your
beltpack transmitter is the problem....if the problem stays with the reciever no matter what different transmitter you try--then the reciver is at fault. This way you at least can narrow down the problem. You can also try relocating the reciever away from the other units and see if that helps it. With those 400mhz range frequencies on a non diversity system--its gonna be hard pressed to not be suceptible to interference--and even crosstalk or interference between like-units.
Another thing to check that is a common problem--which can be a possible problem in your situation too (again--I am not there to SEE what it is actually doing), is the
SQUELCH control for that
unit. It should be a little knob or hole for a screwdriver in the rear of the reciver
unit. Turn it to adjust the squelch--which in a
broad nutshell of an explanation will help you "tighten up the transimission connection" between the transmitter and reciever. Basically, when the
unit is not recieving--it will not
pick up or make any "noise". See how that works and post your answers and I or someone else will gladly help out..and others may have other info for you to try..
On your other note about compressors--what are you trying to achieve with the compressors on the wireless?? Most compressors are great for helping with
channel control and
level control--however they will not help you if your mic's are
clipping, distorting or being overdriven before they even get to the
compressor. Also to answer your quesion--how are your compressors hooked up to the wireless mics? Are they INSERTED using an
insert cable into the wireless channels? If so--your
insert cable may be backwards or not be a real insert cable--a common mistake. Also--check your connections--make sure if you are going from an output that you maintain whether it is balanced or unbalanced--XLR or
TRS / TS type of
phono plug. You cannot mix and match when it comes to those cables when coming out of a balanced output and you use a unbalanced cable.
If thats not it, then answer this--Are your wireless run into the compressors first--and then into a
console channel? If so--bad idea and it won't work or if it does will be intermittent and crappy, because of the extremely low signal... You need to run the signal from the reciever into the
console first, because the
console has a PREAMP which in a nutshell changes the
voltage in an input into a usable
voltage that most other electronic equipment can then do something with. The Output
voltage from most
outboard equipment like CD players, Tape Decks and Wireless Mics are very low
voltage levels and do not travel more then 10 feet before degrading into unusable garbage..they NEED a pre-amp to boost and make them into as usable
voltage level.
Now to the Second part of your question....
Compressors 101... Compressors are great little tools for useing to help control an input
level to not go above a set
level. It does this by compressing the signal--which if you think about water flowing in a trough, its like daming up the water flow with your
hand so that only a small part of the water passes--the rest builds up before its released when it reaches your
hand. So think of a
compressor as your
hand in the water. A
compressor can be used for simple compression on a whole PA
system or a single
channel, and it can be used for tricks like "Ducking" and so on (see below). But overall a
compressor can help with a Sound
System or
channel input to keep levels even or balanced in peaks and dips and from overdriving speakers--however over-use or poor settings of comprerssors can be just as detrimental to a
speaker as the
distortion is because too much compression can cause distortionon. It also causes what is called "breathing" or "pumping"...a notable sound where the levels go from being unclear and "muddy" to suddenly being loud and
clear on lesser levels. A compressed signal HAS to
release that compressed signal--it cannot hold onto it forever or just make it go away.. so the trick and problem most folks
face is setting the
compressor properly for the application. You can HEAR compression if its set hard or the signal is too strong at a
point. It sounds like the sound is being pressed down.. For example: If you get a copy of Whitney Houston's "I Will Always Love You" song you can HEAR the
compressor kick in on her strong vocal notes..and its not much around this because her voice is so powerful.
The Settings of a
compressor are the hardest to figure out. You typically have basic settings in cheap units, like a
THRESHOLD , and ATTACK and a
RELEASE and a RATIO...and on some of the cooler pro compressors you will have more settings to adjust like Frequency/shelving, Peak setting,
Gate, Expander, Hard Knee/Softknee--also known as Overeasy (dbx) and many others. Here is a quick explaination of these basic knobs....
THRESHOLD is the
level at which the input signal activates the
compressor. Ideally, you want the
compressor to barely click on or not move at low and optimum sound levels, and only click on when the levels peak. Low thresholds will compress a LOT of signal that is passed into the
unit, and higher thresholds will allow more signal to pass before it compresses. There is no overall good
threshold setting because signals vary so much..its the one true knob you have to
play with and learn to get right..
ATTACK: this is how fast your
compressor kicks in to a signal that has past the
threshold level. Sometimes a fast attack is desired--other times a slower attack is desired to lessen the "sound" of the actual compression so its not so fast or "overeager" sounding to click the
compressor. Typically--a FAST to Medium fast attack is what works 95% of the time. Depends on the sound and reaction of your
compressor and how the
threshold is set...
RELEASE is sort of the opposite of attack--its how fast the
Compressor RELEASES the compressed signal. If you
release too fast it can sound like pumping if the
compressor is triggered a lot. If you
release slowly however you can end up adding an extra "harmonic" or muddyness to an otherwise
clear signal.. Generally--a medium
release works 90% of the time so as not to be noticable.
RATIO is the setting displayed by a ratio comparision--a 1:1 or 1 5:1 or a 10:1, INFINITY:1 and so on.. You can have as manay as 10 or 15 different ratio settings on a compressor--including Infinity. (the sign for Infinity is an "8" on its side) What this ratio does is tells the compression ratio, or amount of db that is compressed, when the
compressor is triggered. For example: a 4:1 ratio will compress the signal 4db for every 1db over
threshold. a 10:1 will compress 10db for every 1db over
threshold, and so on. Infinity means no matter how much goes over the
threshold it will not get beyond 1db louder. The more compression you set it for, the harder and more noticible the compression can be. The less compression you set, the opposite happens--but it may also not be ENOUGH compression for a very large peak. The higher the compression ratio the more you are making your
compressor into a LIMITER--and that is a device that LIMITS the signal--so the less signal will go pass the
compressor after
threshold is reached. On a poorly set or very LOW
threshold, this will make a signal sound like MUD if it is too heavy in saturation..as all the compressed sound will
build up and
release 1/2 or 2 seconds later or whatever and that is exponentially to the input amount. So try to avoid too much compression--its a killer and can cause mud and
distortion. A Good overall ratio setting is 2:1 or 4:1 for about 90% of the things you will do as a sound guy.. Its great for Vocals, drums & cymbals (4:1 is OK for most drums if the
threshold is right--sometimes you need 6:1 for drums and a really wild drummer), horns and so many other things. It sounds more natural on peaks--and is less noticble by an ear.
Again--the
Threshold is THE KNOB you must learn to use properly... You can use the settings I have suggested above for the others--but the
Threshold is the one you HAVE to learn how to set yourself.. ALL the above settings must be set to work together or you achive nothing in compression.. A great
threshold setting won't do squat if you don't have a ratio or attack/
release setting done. A great Ratio or attack or
release won't do squat if you don't have a good
threshold level for the signal. A good way to
play with and learn what a
compressor does is to sit down with a CD or Mic, a
console and PA or
headphones, and
play with one. Set a low
threshold, input your sound (mic or CD or
instrument) and adjust the Attack and
Release and Ratio and LISTEN to the differences each one does.. Then Go about and do the same to the other knobs. Only after you LISTEN and Learn what compression sounds like will you be able to understand how all the other knobs work together..and then you will want MORE knobs to
play with like Peak and Overeasy and Frequency/Shelving and so on. I will explain what those and other fun knobs you can find on compressors can do later on if you want.. If you have a
Compressor GATE set up--a
comp and a
gate in a single unit--then you will have evcen more knobs and things to set and playwith--including another
GATE Threshold knob that works opposite how a
compressor threshold works.
Thats its for Compresors 101 in a rough nutshell..... Oh yea--DUCKING with a
compressor is setting the
compressor to use a signal as its source for
threshold, and another input signal for the trigger--which will then
DUCK down the original signal. This is mostly used in recording and for commercials. If you hear music in a commercial and then it dips down immediately when the voice talks and pops back up when the voice stops talking, thats DUCKING.
well hope this helps ya.. Others will come and fill in the gaps I have left and I hope they will offer their opinion and insight as well. Feel free to post back any questions or problems and I or someone else will be glad to answer.
Cheers,
-wolf