Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums > LAB Subwoofer Forum
Lowering low frequency noise n stage
Kenny Phillips:
Hello All,
I have a small outdoor stage. I notice quite a bit of low end on stage from the subs which makes sense due to the omnidirectional nature of the lower frequencies. Even when I do not use the subs, I still notice excess low end. Along with that I also measured a bit of an increase in 65hz and 130hz on stage. So I was wondering if anyone has experimented with the idea of actually putting a sub on stage, and feeding it with just enough out of phase sub to cancel some of the low frequency noise. By setting the eq up to be emphasize the 65hz and/or 130hz I may get more of an effect.
My thinking is along the lines of noise cancelling headphones and other applications of inverted feedback.
Any thoughts?
Kenny
Luke Geis:
You will need to change your user name to your real name to get much further here on this forum ( as per the rules ).
I will answer anyway though. Yes that has been done and no it does not work very well. Three real problems with that idea.
1. The sources of noise comes from different locations, so the sub on stage could only ever cancel frequencies at the ONE location that you set it to have maximum rejection. As soon as you move, game over.
2. Now you have sub energy from the stage that will interact with your FOH sound. It won't get better, only worse.
3. You have just added another source of noise that costs money to have an implement and that device just adds more noise to the stage.
One way to reduce rumble on stage is to isolate them more with perhaps a sand barrier, concrete structure or some other way to make the stage not resonate. You could implement a cardiod sub setup, but that requires the subs to be next to each other. However FOH sub content is usually not as bothersome as most think as long as it is not blasting into the mics like crazy. Let me explain.....
The sub energy should really only contain kick and bass for the most part, so while it is obviously going to be heard, if it sounds good and right, it shouldn't be too bothersome. If it makes the whole stage rattle, it is a sonic tuning issue. Reduce the offending frequencies to reduce the soaring rumble. Next thing that most never consider is MONITORS..........Monitors add a crap ton of low end energy that is really of no need. If you are not hi-passing your monitors up to 140-200hz, there is most certainly low end gunk flying out of them all over the stage. Next is the stage floor. Basically a huge diaphragm that is really good at making low notes and mid bass content reproduction. Sureing up the stage and making it sound as dead as possible will do more than you can imagine. If it resonates and makes sound, it will find its way into mics and your FOH mix.
The hardest part to help reduce rumble and over the top low end notes, is to get the band to change their tone. If the bassist is playing a note that makes the whole stage rattle, then he needs to turn down the bass, notch out that frequency ( if he has a graphic or parametric EQ ) and or turn down. If the guitarist has a note that makes things sing, again same thing, turn down the offending EQ band. Good musicians should be willing to help clean up stage noise issues.
Aside from that, it will come down to PA system tuning. Too much of a good thing is still too much. Getting the sound to be clean and a little more natural can really help clean things up. If the sound out front is bigger than life in every way, it will find its way back into a mic which further reinforces that sound out of the PA. Most of the offence I find though, exists from the monitors. The monitors will make a wooden, resonant stage really woof up and make for a sound guys worst nightmare.
Kenny Phillips:
Luke,
Thanks for your gracious answer in spite of my name faux pas. Not sure how to change the name other than create a new profile with my real name. Will fix it.
Looks like beefing up the stage as well as damping with sand is first order of business. Planning on buying a cardioid sub and also placing the mains a little further of to the side of the stage. Its just an open sided shelter 12x12 stage in the back yard, but my goal is to do it as well as possible.
Once again thanks
Kenny Phillips
Luke Geis:
My caveat to the cardioid subs placed on each side of the stage is this: Cardiod subs reject predominately in the rearward plane, which means if they are side stage, they will be ineffective at keeping energy off the stage. If you had a center cluster of subs, this would be a more viable solution.
I feel that making the stage non resonant will be the biggest help, followed by getting the monitors low end under control, then tuning the FOH system to not excite things on the stage. Cardioid subs are not as much help as their solution appears to offer. It requires a very specific situation for them to be effective; at least objectively.
Tim McCulloch:
--- Quote from: Luke Geis on June 19, 2018, 02:18:06 PM ---My caveat to the cardioid subs placed on each side of the stage is this: Cardiod subs reject predominately in the rearward plane, which means if they are side stage, they will be ineffective at keeping energy off the stage. If you had a center cluster of subs, this would be a more viable solution.
I feel that making the stage non resonant will be the biggest help, followed by getting the monitors low end under control, then tuning the FOH system to not excite things on the stage. Cardioid subs are not as much help as their solution appears to offer. It requires a very specific situation for them to be effective; at least objectively.
--- End quote ---
A center cluster of subs will put about half it's energy right on the stage.
Navigation
[0] Message Index
[#] Next page
Go to full version