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  #1  
Old 02-26-2014, 08:49 PM
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Need surround sound advice...

I have been tasked with coming up with what I guess would be a surround sound system for a large hall with tile floors and hard walls. Ceiling is about twenty feet and this thing is about the size of a basketball court.

The speakers are there. Two monsters from some old rock band and two smaller one that fit on stands. These are real theater speakers and the big ones are about five feet tall and weigh over 100 pounds each.

There are two speakers mounted on the stage and two near the back of the hall. The big ones are in the back.

The problem is the sound towards the back of the hall is somewhat distorted. Things are great toward the front but it get pretty messed up towards the back.

I have asked our sound people if they know the cure and they said when I needed sound recorded to give them a call. Until then I need to find someone who knows how to set up a speaker system since that's not something they do.

Buying used equipment is the way I intend to go since there is always someone who is needing fast cash, so..... What am I looking for?

Some sort of sound processor? A home surround sound system? Is there something to the principal of a delay for the rear speakers?

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  #2  
Old 02-26-2014, 10:26 PM
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I've re-read this multiple times and I'm having trouble envisioning the existing setup. Is it possible to snap a few photos or just sketch the layout and post it?

At the least, I'd say you need an audio processor or a delay unit. You can get an older Vortex unit for pretty cheap that has quite a bit of processing power and may have a delay built in.

Do you have a list of the existing equipment?
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  #3  
Old 02-27-2014, 12:51 AM
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Details will be coming soon. I will have to post photos of the speakers since there is really no way I can accurately describe them except to say they are massive.

And there is, of course, the chance that I already have everything I need and just don't know it.

Photos coming.....
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  #4  
Old 02-27-2014, 10:14 AM
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My questions would be:

How old is the system?
Do you live in a humid environment?
What type of connectors are in the system?
Did the system ever sound good or has it always sounded like this?
Is the system bi-amped or tri-amped?
Is there a mixing console?
Is there any acoustic treatment on the walls?

If you can take pictures, try to shoot as many of the front and back of the equipment as possible, particularly close ups of the connectors. It would also help to see pictures of the front of the equipment when it's powered up to make sure all the LED's are lit properly.

When I have to deal with a situation like this, the first thing I do is go to every single piece of equipment and spin and slide the controls to their full extent. With the system power off, go to each control and spin or slide it all the way both directions and then return it to the position it was to start with.

Then, go to the connections and if you have any 1/4" (headphone type), jack them in and out a few times each. Do this for the entire system from inputs to the speakers if they have that type of connection. These type of connectors can be degraded by age and environmental conditions.

Hope this gives you a start.
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  #5  
Old 02-27-2014, 10:54 AM
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I consulted for a group of acoustical engineers for a few years. This kind of project is right up their alley. If you want this to be a success I suggest you contact a group with similar skills.
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  #6  
Old 02-27-2014, 11:30 AM
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What are you using it for? Just general PA system? A band would be fine in such a small room without much reinforcement. Your first reflection is going off the roof and the floor, so if the place is filled you won't worry much about the highs coming off the floor. You can control the bass using bass traps. Other than that you really need stuff that absorbs energy but you can do that with stuff from the hardware and fabric store.
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  #7  
Old 02-27-2014, 11:39 AM
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Quote:
Originally Posted by Kuan View Post
What are you using it for? Just general PA system? A band would be fine in such a small room without much reinforcement. Your first reflection is going off the roof and the floor, so if the place is filled you won't worry much about the highs coming off the floor. You can control the bass using bass traps. Other than that you really need stuff that absorbs energy but you can do that with stuff from the hardware and fabric store.
The walls are all hard concrete block. I have considered picking up some acoustic panels, like Dilbert lives in, from Habitat for Humanity in Dallas since it seems like they always have a bunch of those cheap, but it has also been suggested to me that buying some 1/2 insulation panels from Lowes and covering them with wool felt would also work and might even look better.

I am not talking about panelling the entire room, just a few spaced out there and there. Is this worth considering?

And..... The only time this would be used is when the room is filled with people and that seems to really make a difference. The room can sound fine until it is filled with those darn humans and their silly wandering around and moving and stuff! Why, it's almost like they were there to enjoy themselves.

Anyway, when the room is filled the sound towards the back tends to get distorted. My main goal is to make the sound as good in the back of the room as it is in the front when the room is filled with people who are wandering around and talking and what not.

Photos..... They are coming.
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  #8  
Old 02-27-2014, 12:00 PM
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What does a few panels mean? Your goal is to control the first reflection and break up the standing waves. So you will need soft panels to absorb, and hard ones to reflect the waves in different directions. So imagine the speaker as a point source that generates a cone of sound. On axis will be loudest of course, and you want to draw this line and stick your acoustic treatment right where it hits the wall.

And then also you can "tune" the bass by moving the speakers closer or farther away from the wall. The closer they are the more the wall will reinforce the bass. The next easiest thing to do is never place the speaker equidistant from the back and side. You want to avoid a square, it's the reinforcement thing. The walls will reinforce the same frequency twice.

But if you don't want to do it quasi scientifically you can just get a bunch of odd sized panels and work on speaker placement and aiming. That will get your at least halfway there.
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  #9  
Old 02-27-2014, 02:02 PM
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Quote:
Originally Posted by Kuan View Post
What does a few panels mean? Your goal is to control the first reflection and break up the standing waves. So you will need soft panels to absorb, and hard ones to reflect the waves in different directions. So imagine the speaker as a point source that generates a cone of sound. On axis will be loudest of course, and you want to draw this line and stick your acoustic treatment right where it hits the wall.

And then also you can "tune" the bass by moving the speakers closer or farther away from the wall. The closer they are the more the wall will reinforce the bass. The next easiest thing to do is never place the speaker equidistant from the back and side. You want to avoid a square, it's the reinforcement thing. The walls will reinforce the same frequency twice.

But if you don't want to do it quasi scientifically you can just get a bunch of odd sized panels and work on speaker placement and aiming. That will get your at least halfway there.
This is just the type of information I am looking for. There is no need to restrain yourself for fear of hurting my feelings. I have to give a lot of people news that is hard for them to take at first, but I have never had anyone tell me I steered them wrong. I need to do this as right as I can the first time since there is no way I will have the time to do it over.

Photos soon......
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  #10  
Old 02-27-2014, 02:06 PM
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One might almost call it sound advice.
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  #11  
Old 02-27-2014, 03:56 PM
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Quote:
Originally Posted by Jooseppi Luna View Post
One might almost call it sound advice.
ba-dum-tiss! You're on a roll today!
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  #12  
Old 03-01-2014, 02:45 PM
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I found a picture of a high school auditorium we did a couple years ago. The sound treatment is the alternating reflectors on the walls and the suspended paneling in the ceiling. The walls are cinder block.

Sorry for the fuzzy picture.

We also did a gym recently that's all block and about the size and shape you're talking about. I'll try to get some pics next time I'm over there.
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