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Author Topic: Rear speaker in reverbrant room  (Read 9228 times)

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Rear speaker in reverbrant room
« on: March 26, 2014, 07:28:11 AM »

Hi, is there anybody who has experience with using rear speakers (delayed & flipped phase) to mitigate reverbs in small hall (13x23meters)? Does it make any sense? Where should be those speakers located? Corners/center?

Btw, in my installation we can't use mounting brackets and hang tilted front speakers from the truss.. So I suppose the best solution is putting them on stands close to the wall on both sides of the stage.
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Brad Weber

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Re: Rear speaker in reverbrant room
« Reply #1 on: March 26, 2014, 08:38:17 AM »

Hi, is there anybody who has experience with using rear speakers (delayed & flipped phase) to mitigate reverbs in small hall (13x23meters)? Does it make any sense? Where should be those speakers located? Corners/center?
Reverberation is a factor of the room and won't be changed, in fact the added speakers will likely just make things worse by adding more sources putting more energy into the room.
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TJ (Tom) Cornish

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Re: Rear speaker in reverbrant room
« Reply #2 on: March 26, 2014, 09:18:22 AM »

Hi, is there anybody who has experience with using rear speakers (delayed & flipped phase) to mitigate reverbs in small hall (13x23meters)? Does it make any sense? Where should be those speakers located? Corners/center?

Btw, in my installation we can't use mounting brackets and hang tilted front speakers from the truss.. So I suppose the best solution is putting them on stands close to the wall on both sides of the stage.
In addition to Brad's great information, time alignment - especially if you're trying to do some kind of active cancelling of reverb noise, ranges from very difficult to impossible.  You may be able to fix the problem for one seat in the house, but that will likely not improve the situation anywhere else and/or make it worse.

Better to treat the root of the issue - sound treatment, reduce stage volume, etc.
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Tim McCulloch

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Re: Rear speaker in reverbrant room
« Reply #3 on: March 26, 2014, 10:27:12 AM »

Hi, is there anybody who has experience with using rear speakers (delayed & flipped phase) to mitigate reverbs in small hall (13x23meters)? Does it make any sense? Where should be those speakers located? Corners/center?

Btw, in my installation we can't use mounting brackets and hang tilted front speakers from the truss.. So I suppose the best solution is putting them on stands close to the wall on both sides of the stage.

You cannot "cancel" reverb.
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Re: Rear speaker in reverbrant room
« Reply #4 on: March 26, 2014, 10:51:07 AM »

You cannot "cancel" reverb.

I require at least 48 hours notice to cancel any reverb....
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Tim McCulloch

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Re: Rear speaker in reverbrant room
« Reply #5 on: March 26, 2014, 01:07:14 PM »

I require at least 48 hours notice to cancel any reverb....

It takes a reservation to get a D9 EQ?
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Brad Weber

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Re: Rear speaker in reverbrant room
« Reply #6 on: March 26, 2014, 01:42:56 PM »

I require at least 48 hours notice to cancel any reverb....
So that's how long it takes to collect a bunch of dead cats and mount them to the walls.
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Re: Rear speaker in reverbrant room
« Reply #7 on: March 26, 2014, 01:58:56 PM »

So that's how long it takes to collect a bunch of dead cats and mount them to the walls.

Fe-lining the room???
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Mark McFarlane

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Re: Rear speaker in reverbrant room
« Reply #8 on: March 26, 2014, 02:19:43 PM »

So that's how long it takes to collect a bunch of dead cats and mount them to the walls.


I wish my brother was still alive, he would have loved this response, and he would have volunteered to nail them in place.  LMAO....
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Mark McFarlane

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Re: Rear speaker in reverbrant room
« Reply #9 on: March 26, 2014, 05:32:31 PM »

Fe-lining the room???

Great idea, I'l surely find some plugin in my X32 for using this...
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Re: Rear speaker in reverbrant room
« Reply #10 on: March 26, 2014, 05:51:13 PM »

Great idea, I'l surely find some plugin in my X32 for using this...

Can't be done with just the usual Cat5.  Maybe Cat5K...
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ADSfa sdf asdfa sd

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Re: Rear speaker in reverbrant room
« Reply #11 on: March 26, 2014, 06:00:49 PM »

In addition to Brad's great information, time alignment - especially if you're trying to do some kind of active cancelling of reverb noise, ranges from very difficult to impossible.  You may be able to fix the problem for one seat in the house, but that will likely not improve the situation anywhere else and/or make it worse.

Better to treat the root of the issue - sound treatment, reduce stage volume, etc.

Thanks Tom & Brad! I was just wondering if this is possible, now i know I should focus more on absorbers rather than playing with impossible...
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Don Boomer

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Re: Rear speaker in reverbrant room
« Reply #12 on: March 26, 2014, 06:21:39 PM »

As Brad said, reverberation is a factor of the room.

What you can do by using remote speakers is to change the ratio of direct sound to reverberant sound by putting them closer into the direct field of a speaker.  So the idea is to not increase the overall level of sound in the room but to get everyone close to a speaker.  Easier said than done.

If everyone wore headphones there would be no reverb, right.  So if everyone sits within ten feet of a speaker (depends on the room of course) then they will be hearing more direct sound and less reverb.  Now the problem is you have to offset time to adjust for the difference in arrival time because of the different distances and then add in the Hass effect.  Depending on a number of things this could get you moving in a better direction ... at least for more listeners.
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John Rutirasiri

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Re: Rear speaker in reverbrant room
« Reply #13 on: April 02, 2014, 01:37:41 AM »

Hi, is there anybody who has experience with using rear speakers (delayed & flipped phase) to mitigate reverbs in small hall (13x23meters)? Does it make any sense? Where should be those speakers located? Corners/center?

Btw, in my installation we can't use mounting brackets and hang tilted front speakers from the truss.. So I suppose the best solution is putting them on stands close to the wall on both sides of the stage.

Can you tell us what speakers were installed?  Maybe the reverb issue is compounded by speakers that do not have good pattern control or directivity, or just wrong type of speakers for the venue. 

Are you (aggressively) gating the mics? This can help tremendously in an acoustically-challenged room.

-JR

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Re: Rear speaker in reverbrant room
« Reply #14 on: April 02, 2014, 04:31:38 AM »

Are you (aggressively) gating the mics? This can help tremendously in an acoustically-challenged room.

-JR

No.  In addition, hard gating will be audible and may well introduce other problems.
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John Rutirasiri

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Re: Rear speaker in reverbrant room
« Reply #15 on: April 06, 2014, 03:12:49 AM »

No.  In addition, hard gating will be audible and may well introduce other problems.

Life is full of compromises....sometimes it is necessary to gate aggressively.  Audible?  Perhaps, but we're not talking as bad as compression and pumping.  Not sure what other problems you mean though.  Speech has short decay.  You can set the release time to be fairly fast so as to shut the vocal mics as soon as possible.  This helps tremendously in a reverberant space.   We are only talking about vocals and speech here, am I correct?

JR
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Ivan Beaver

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Re: Rear speaker in reverbrant room
« Reply #16 on: April 06, 2014, 09:20:30 AM »

Life is full of compromises....sometimes it is necessary to gate aggressively.  Audible?  Perhaps, but we're not talking as bad as compression and pumping.  Not sure what other problems you mean though.  Speech has short decay.  You can set the release time to be fairly fast so as to shut the vocal mics as soon as possible.  This helps tremendously in a reverberant space.   We are only talking about vocals and speech here, am I correct?

JR
Part of the problem with hard gating a vocal mic is the sound it makes.  When the mic is open you hear not only the person speaking-but also the room/PA getting back into the mic.

When it shuts off hard-that sound is different.  I have had a number of "lay people" complain about this "odd sound" when I tried to do it year ago in an automix situation.

And the other problem is where to do set the threshold?  If you set it to keep all the sound except a loud speaker out, then when somebody who is softer spoken will not trigger it and it gets real choppy sounding and WORSE than not using a gate.

If you set the threshold real low for quiet speaker-then any sound (person coughing-door closing-HVAC coming on etc) will trigger the mic open and the "sound" will constantly be changing in the sound system-which can get quite annoying.
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John Roberts {JR}

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Re: Rear speaker in reverbrant room
« Reply #17 on: April 06, 2014, 11:33:13 AM »

Part of the problem with hard gating a vocal mic is the sound it makes.  When the mic is open you hear not only the person speaking-but also the room/PA getting back into the mic.

When it shuts off hard-that sound is different.  I have had a number of "lay people" complain about this "odd sound" when I tried to do it year ago in an automix situation.

And the other problem is where to do set the threshold?  If you set it to keep all the sound except a loud speaker out, then when somebody who is softer spoken will not trigger it and it gets real choppy sounding and WORSE than not using a gate.

If you set the threshold real low for quiet speaker-then any sound (person coughing-door closing-HVAC coming on etc) will trigger the mic open and the "sound" will constantly be changing in the sound system-which can get quite annoying.
Part of the magic with automatic mixing that uses the "Dugan" algorithm, even as the gain from individual microphones gets manipulated up and down, the background noise remains steady due to NOM=1.

JR
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Re: Rear speaker in reverbrant room
« Reply #18 on: April 06, 2014, 12:19:05 PM »

Life is full of compromises....sometimes it is necessary to gate aggressively.  Audible?  Perhaps, but we're not talking as bad as compression and pumping.  Not sure what other problems you mean though.  Speech has short decay.  You can set the release time to be fairly fast so as to shut the vocal mics as soon as possible.  This helps tremendously in a reverberant space.   We are only talking about vocals and speech here, am I correct?

JR

See Ivans excellent reply.

Downward expansion or a decent auto-mixer will work as will manually riding faders.   Hard gating will sound bad and will mark you as an amateur no matter how long you've been "in the biz".
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Tim Perry

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Re: Rear speaker in reverbrant room
« Reply #19 on: April 06, 2014, 07:54:38 PM »

Hi, is there anybody who has experience with using rear speakers (delayed & flipped phase) to mitigate reverbs in small hall (13x23meters)? Does it make any sense? Where should be those speakers located? Corners/center?

Btw, in my installation we can't use mounting brackets and hang tilted front speakers from the truss.. So I suppose the best solution is putting them on stands close to the wall on both sides of the stage.

Jenda, To deal with highly reverberant rooms first you tilt the main speaker down so the HF energy goes into the audience and not the back wall, ceiling etc.   This is pretty magical in itself. if you haven tried it you will be surprised at its effectiveness. 

The nest step is to set up a delay speaker(s). Typically they will be placed halfway to the back wall  and aimed roughly in the same direction as the main speakers. The delay is  88 milliseconds per 100ft. Often a digital delay allow you to select in feet, meters, or time which makes it pretty easy to set up.

Setting the delay for slightly longer then the actual distance gives the effect that the sound is coming from the main stage area rather then the delays.

The advantage here is main volume can be lower, speaker are not aimed at walls, reverb is less,  feedback issues from mains is less.

The disadvantage is if the talent walks into the delay field he hears the delay which may disconcert him/her and make it difficult to sing on pitch.

 
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Tim McCulloch

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Re: Rear speaker in reverbrant room
« Reply #20 on: April 06, 2014, 08:20:00 PM »

Setting the delay for slightly longer then the actual distance gives the effect that the sound is coming from the main stage area rather then the delays.

Ah, the Haas Precedence Effect.  I've found that using additional delay (beyond what is needed for a phase alignment) doesn't provide enough benefit to justify the messing with the alignment.

Quote
The advantage here is main volume can be lower, speaker are not aimed at walls, reverb is less,  feedback issues from mains is less.

The disadvantage is if the talent walks into the delay field he hears the delay which may disconcert him/her and make it difficult to sing on pitch.

I don't think it would be any worse than simply being X distance from the mains.  Even if there was no delay ring/zone/fills, a performer or presenter that far from the main PA would still be subject to the same speed of sound, time-of-flight.  Acoustic or electronic, it's still distance=time.
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Tim Perry

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Re: Rear speaker in reverbrant room
« Reply #21 on: April 06, 2014, 08:50:33 PM »

Ah, the Haas Precedence Effect.  I've found that using additional delay (beyond what is needed for a phase alignment) doesn't provide enough benefit to justify the messing with the alignment.

I don't think it would be any worse than simply being X distance from the mains.  Even if there was no delay ring/zone/fills, a performer or presenter that far from the main PA would still be subject to the same speed of sound, time-of-flight.  Acoustic or electronic, it's still distance=time.

It's Kind of funny to hear someone announce from the back of a large venue and hear their voice slow down as they try to sync with the sound.

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Re: Rear speaker in reverbrant room
« Reply #21 on: April 06, 2014, 08:50:33 PM »


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