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Author Topic: Help with evening out sub in an amphi  (Read 1490 times)

Miguel Dahl

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Re: Help with evening out sub in an amphi
« Reply #10 on: April 24, 2021, 08:28:40 am »

Do the old audiophile trick:
Place the sub in the middle of the audience area, then walk around possible sub placement areas and listen for the best sound.

Humm.. I didn't get it. I have two subs. Both need to be against the back wall since the amphi is retractable. The room is a big cube. So "perfect" lobes will happen, but I want A) To dampen the energy at FOH which is straight above the subs, and B) try to even out somewhat in the seating.

A is of more importance than B, as there will be uneven coverage no matter what, but I'm trying to look into if it's possible to dampen the energy which goes straight up from the subs, so the operator of the console can hear a spectrum which is closer to the what the most of the seats are hearing, comparing to now. When it comes to Sub-energy that location might as well be in china, it's not representative of what the rest of the room is getting.
« Last Edit: April 24, 2021, 09:50:56 am by Miguel Dahl »
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Tim McCulloch

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Re: Help with evening out sub in an amphi
« Reply #11 on: April 24, 2021, 10:02:10 am »

Humm.. I didn't get it. I have two subs. Both need to be against the back wall since the amphi is retractable. The room is a big cube. So "perfect" lobes will happen, but I want A) To dampen the energy at FOH which is straight above the subs, and B) try to even out somewhat in the seating.

A is of more importance than B, as there will be uneven coverage no matter what, but I'm trying to look into if it's possible to dampen the energy which goes straight up from the subs, so the operator of the console can hear a spectrum which is closer to the what the most of the seats are hearing, comparing to now. When it comes to Sub-energy that location might as well be in china, it's not representative of what the rest of the room is getting.

You are fighting a loosing battle, Miguel.  The acoustic problems created by the installation cannot be fixed without physically moving the subs or putting the "booth" on vibration isolating suspension.  As for the poor folks sitting in front of the subs... well, they're fucked.  No amount of electro-wizardry can change that.
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Kevin Maxwell

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Re: Help with evening out sub in an amphi
« Reply #12 on: April 24, 2021, 10:40:53 am »

Do you have a picture of this room that you can post here? When you say back wall (where you seem to be saying is where the subs need to be) are you referring to the back of the stage wall or the back of the room behind where the people are sitting? And I am not sure where the mix position is that is usually called FOH (front of house) that isn't in the front of the house but usually in the back of the house. FOH is used to refer to where you sit to control the sound that is coming out of the front of the house.
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Scott Bolt

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Re: Help with evening out sub in an amphi
« Reply #13 on: April 24, 2021, 01:23:12 pm »

You are fighting a loosing battle, Miguel.  The acoustic problems created by the installation cannot be fixed without physically moving the subs or putting the "booth" on vibration isolating suspension.  As for the poor folks sitting in front of the subs... well, they're fucked.  No amount of electro-wizardry can change that.
I'm going to have to 2nd Tim here.  This is just physics in action.

For wedding receptions, I frequently setup what you have (2 subs stage left and right near the rear wall).  This has the effect of putting a hyper bass node directly in front of the speakers and some number of feet in front of them (as well as one directly behind them which is a terrible place to sit with this setup ;)).  The rest of the venue (usually a large banquet hall) has much less bass so people can talk .... which really works out well for THAT application.

If ascetics are more important than the sonics, the sonics are .... well Tim said it best ;).
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Mac Kerr

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Re: Help with evening out sub in an amphi
« Reply #14 on: April 24, 2021, 02:29:12 pm »

Not an option, they stay on the ground, in the back..

If under the audience is the only place they can be and itís too loud for the sound man, turn them down.  The soundman is in the audience, if itís too loud for them itís too loud for the audience. There is no such thing as even coverage with subs indoors.

Mac
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Dave Garoutte

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Re: Help with evening out sub in an amphi
« Reply #15 on: April 24, 2021, 04:57:19 pm »

What if you put some delay on one of subs to get cancellation at FOH?
It would effect the audience too, but you already said it sucks.
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Scott Bolt

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Re: Help with evening out sub in an amphi
« Reply #16 on: April 24, 2021, 07:06:30 pm »

If under the audience is the only place they can be and itís too loud for the sound man, turn them down.  The soundman is in the audience, if itís too loud for them itís too loud for the audience. There is no such thing as even coverage with subs indoors.

Mac
Yep.  Really no such thing as even coverage period.  It is really just as even as it can be.

Best case for subs would be center clustered in front, outside with no boundaries to reflect and cause nodes.

In some indoor areas, bass coverage is just crap right out of the gate with nearly no hope of anything resembling a good sound for the night.  All you can do is adjust the volume to make it at least .... eh .... in most areas.

I had one room I used to play that was a subwoofer mud machine.  All you could do was turn down the bass .... which eliminated the punch, but at least cleaned up the acoustics for the rest of the music.
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raymondsoly

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Re: Help with evening out sub in an amphi
« Reply #17 on: April 24, 2021, 07:30:34 pm »

Fly the subs?

use only one side for the subs..defeat the power alley. I've done this in several difficult venues/situations it worked out better than the original "mushy" subs...of course YMMV.
Ray
« Last Edit: April 24, 2021, 07:38:17 pm by raymondsoly »
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Miguel Dahl

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Re: Help with evening out sub in an amphi
« Reply #18 on: April 29, 2021, 01:50:13 pm »

I tried my best. I guess you get the picture.

I was wondering if its possible to dampen the energy at the back wall, straight up, where some seats are, and also FOH. The lobes which will occur in the room are of course due to physics.  Power alley is nothing to do about, it's just there when the subs are mirrored. I guess a third sub would actually help, to create more lobes, but not as big differences between positive and negative if one "offset" it. That would even out the total for the room at least. But spacing the two subs I already have would still create quite big peaks and dips, even if I can offset them.

I did not paint in the lobes, but you get the idea, lobes between the walls, but in general the area marked green is "ok" but with the natural lobes occuring, that area is the biggest in in seating. So where the tuning is now, most people get an on average ok response. I've tuned the system for "where most people sit".

My thought was initially to lay the subs flat horizontally, then raise one of them to approx 1.1m above ground to make it cancel itself out at 65Hz in the vertical direction (calculated for that the acoustical centre is about 1.4m from the ground (can't remember if this is correct in fact), but fiddle with the output level relative to the one on the floor. So "just one sub will be playing vertically, at a given bandwidth".. but since I suck at maths and cant model what the sub on the floor would do, I have no idea of what could happen.

The thought was that cancel somewhat upwards, and the more horizontal the angle gets, the more coherent both subs will work together.

« Last Edit: April 29, 2021, 02:09:11 pm by Miguel Dahl »
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Dave Garoutte

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Re: Help with evening out sub in an amphi
« Reply #19 on: April 29, 2021, 03:59:30 pm »

Is it possible to scoot the subs forward to under the middle of the seating, when it's pulled out?
This would de-couple them from the back wall, put them closer to the center of the listening area, and away from FOH.
Then you could turn them down, since they would be closer to most of the audience.
« Last Edit: April 29, 2021, 04:03:16 pm by Dave Garoutte »
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Re: Help with evening out sub in an amphi
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