surround sound

[AlexD]

I am going to be instaling a surround sound system into my schools theatre. We have 6 places where wires have been instaled into the wall (3 on iver side).

I dont not know what speakers to get ior what amp to get to run them. So could you please advise me on what to get?

If it makes a difrence it will be running through SCS cueing softwere.

[headcrab]

It depends on how large your theater is. For our venue (about 70' from front to back, probably room for 200 people) we can get away with a RMX850 by QSC. It is 200Wx2 into an 8 ohm load. Most speakers are 8ohms.

The speaker must be able to handle the power the amp can deliver. Don't get a 50W speaker and a 300W amp. If you overdrive a speaker, the speaker can be damaged. It has been said that an underpowered amp that starts clipping can damage speakers rated for more power.

If you can afford it get a larger amp than you think you need. You can always turn down the gain, and if you decide to expand later, you have the capability.

[AlexD]

Ok if i can tell you the size of the hall could you recomend me something? Im quite new to all this as in i know bearly anything to do with setting up a system. Just to be sure the wat output of an amp isnt devided up to the speakers? so 6 50w speakers dosent meen u need a min on a 300w amp u need a 50w amp with 6 outputs?

[NickJones]

Yup, thats correct. As headcrab said, sticking to much power in can fry them. So make sure you buy an amp that matches the wattage of your speakers. Whoever sells you this should (you hope) be able to sort you out with a system.

As for your question about the cueing software would work fine, it would be no different with a surround sound system, you would just need to select the Aux Sends it goes to.

Nick

[museav]

Answering your question can get rather involved and requires knowing the space, the goals for the system, how it will be used, your budget for the speakers, etc. After reading your posts on this project I really have to be honest and state that I think you would be best served to get a local professional to help determine what it is you really need and how it all goes together. Forums are great for addressing specific questions or general discussions but it is simply not practical or appropriate to try to design a system via a forum like this.

Originally Posted by headcrab

If you can afford it get a larger amp than you think you need. You can always turn down the gain, and if you decide to expand later, you have the capability.

A common misconception. The 'gain' controls on an amplifier do not adjust or limit the output, they instead attenuate the signal between the amp inputs and the amplification circuit, which in most professional amplifiers is a fixed gain circuit. So an amplifier is always capable of full output regardless of the level control setting, the level control simply varies the input signal level required to get that output. This is important to understand as something like someone dropping a mic could still result in not only full rated output, but full output of a severely clipped and distorted signal.

Originally Posted by NickJones

So make sure you buy an amp that matches the wattage of your speakers.

Another common misunderstanding caused by applying band/PA sound concepts to installed audio systems. For permanent installs a more effective approach is to determine the levels and headroom that you want the system to provide at the listeners and then work back through the room to the speaker sensitivity and from that to the power required. The speaker power rating is then merely a verification that the speakers can handle the power required and not actally part of determining the power required. That is quite different than portable systems where the goal is not a specific result in a defined application but rather the most flexibility to support any variety of applications.

Maybe you start to see now why forums are not always a good way to try to design a system.

[AlexD]

Ye this is much more complcated than i thought it was going to be... I will get some one in to help me out on this one shame that its the begining of the school holday and the site is closed... oh well\

Thank you for your help

I dont need any mroe help on surround sound i am not going to be instaling it now.

[AlexD]

I was wondering how do you get suround sound to work through a mixer? From what you guys have told me you run it through aux. Do you have to run all speaker outputs through aux?

[Edit by Moderator: This post merged here from its own thread, for continuity purposes.]

[hsaunier]

Take Brad's advise. If you try to do this without a very clear understanding of the intended use of the room, and without very experienced help, you will end up spending more money in the long term, after several dissapointing attempts with an undesired outcome.

[AlexD]

I was wondering how suround sound works thorugh a mixer. From what you guys have told me alredy it runs through aux. How exacly do u run it though aux? Do u need to have as meny aux chanles as there is speakers? Do u have to run normal speakers though aux?

[Edit by Moderator: This post merged here from its own thread, for continuity purposes.]

[gafftaper]

First off an important point is:
Why do you want to run surround sound. The vast majority of pro-theaters are running mono sound. Why? Because Surround sound or (and to a lesser degree stereo) only works for one seat in the theater. Everyone else is either too close or too far away from the other speakers to get the correct effect. Someone sitting in the back left corner is generally only going to hear the rear surround speaker. That's not very good. Stereo is also a problem because you have a single row of seats down the middle that sound good but the rest don't. The exception to this rule is if you are in a unique seating space like a black box or theater in the round. In my theater I have speakers all over the place that I use to send specific sound effects to unique locations... But the mains come out mono.

As for how you would hook it up:
That depends a lot on your sound board. Some boards are set up to run surround more easily while others are more difficult. What make and model board do you have? We can tell you how it could be done.

As for the headroom concept mentioned above:
We installed an 18" sub woofer in my theater. Even though the amp was supposedly "ideally matched" by an "expert" it was a 1400 watt sub with an amp bridged to 1800 watts. In order for the amp to hit those really deep notes it has to pump out everything it's got. The more power the amp puts out the more distortion it creates. The end result was on the really big deep notes, the speaker would "bark" or go "thhhhpppppppppph" in a very bad way. We upgraded to an amp putting out 3000 watts and now it sounds great. The amp doesn't have to work hard to put out the power needed to drive the speaker... this is head room. True we could potentially damage the speaker if we cranked the amp all the way up. But the truth is you are actually likely to do more damage by under powering than over powering a speaker.