# Outdoor Room Modes!?



## Lumen (May 17, 2014)

Some buddies of mine played an outdoor gig on a concrete stage under a wooden, shingled roof. All four sides were open to the surrounding fair. Word has it (I wasn't there) that band members experienced a strange phenomenon with certain bass notes: the frequencies seemed to reinforce and cancel just like they would in a typical, enclosed listening room! 

For example, the low-C note (65 Hz) on bass guitar would sound out just fine, but the musician could hardly hear "G" (98 Hz). This was through the on-stage monitors. I was told the audience could hear all notes just fine. But the band's performance was poor because they couldn't hear themselves play. Any musicians out there experience anything similar?


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## Sangram (Dec 18, 2013)

Floor reflection from the concrete stage maybe? Or cancellation between two adjacent monitors?

Does sound odd though, normally never happens either side of the stage with f<100Hz.


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## FOH (Aug 27, 2012)

Not a musician, however I've mixed live shows in every conceivable acoustic environment one could imagine. 

What you describe sounds like simple destructive interference from the structure above them. 

Typically outdoors, or when there's a lack of adjacent boundaries, such as sidewalls etc., whatever acoustic interaction that does occur (be it destructive interference or constructive "power alley" type summation) is very easy to hear.


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## Lumen (May 17, 2014)

Sangram said:


> Floor reflection from the concrete stage maybe? Or cancellation between two adjacent monitors? Does sound odd though, normally never happens either side of the stage with f<100Hz.


Reflection and cancellation is what most band members thought. Now they're changing their story to bass feedback and talking about getting a sound man. Isn't that what a Behringer Feedback Destroyer does?

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## Lumen (May 17, 2014)

FOH said:


> Not a musician, however I've mixed live shows in every conceivable acoustic environment one could imagine.


Live close to Indiana and need a job running sound? 

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## FOH (Aug 27, 2012)

Indianapolis, yes
Running sound, sorry no. 

Curious however, what type of venues, what type of PA?


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## Lumen (May 17, 2014)

FOH said:


> Indianapolis, yes Running sound, sorry no. Curious however, what type of venues, what type of PA?


 ...errrr. You got me there! I'm just a friend of the band so I don't know much about their performances except they play indoor and out. They don't seem too concerned about the mishap, but maybe they should be!

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## FOH (Aug 27, 2012)

Hey no problem, just curious.
I'm not actively involved in FOH work much anymore, my focus is HT and music playback via my HT rig.


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