live sound question

[guitarmonkey]

so, i am pretty new to gearslutz and i have a live sound question, is that allowed here?

i'm a worship pastor at a church. our auditorium is roughly 50' wide by 100' long and we are getting ready to re-orient the room sideways, so it will be 100' wide by 50' long. the ceiling is 14' or 15' high. walls are plaster covered brick/masonry. carpeted concrete floors. modern padded chairs instead of pews.

how much PA do i need in this room. i thought i knew, but i'm second guessing myself, now.

how many sub cabs? how much sub power? how many mid-hi cabs? how much power?

we have an allen and heath gl series 32 channel board, and good mics and good cables. we're currently using 2 mackie powered subs (srs1500) and 2 mackie powered mid-hi cabs (srm450) for our mains.

thoughts, links to other sites or books and opinions are all welcome.

thanks!
g-monkey

[tINY]

How much you need depends on a lot of things. If you are looking to do this on the cheap, then the coverage angle is important. You'll probably want to go mono in a space with those dimmensions.

Some of the biggest gains can be made by acoustic treatments and proper placemnent of the cluster. You may want to talk to an acoustician familiar with setting up worship spaces. Ask around at other congregations that have remodeled or upgraded sound systems in the last couple of years.

The biggest problem is often finding a ballance between the music and the spoken word (not to mention that music styles tend to change every decade or so).



-tINY

[doug_hti]

at the risk of being crucified by the room crusaders:

I won't disagree with the importance of the room, because there are a lot of nasty rooms with problems for days....but....on a budget, with today's technology, I feel that (many times) more bang for the buck can be achieved with better boxes setup and flown properly, then with spending 10's of $k's on an acoustician consulting and room treatment(that never turns out to be enough), when no budget is left for a good sounding rig.

I think the pattern control of PA's has really improved so much in the last few years, that many times just putting in the enough boxes to get direct sound to the listeners and putting in the right boxes, will yield a better $ for $ result.

I've been in so many rooms, where the house guys will talk about how bad the room is, etc, etc...and sure it's not amazing, but most of the time it's just that they have a horrible untuned, non-time aligned, underpowered, improperly flown PA, in a mediocre room that all together sounds awful.

And I know it's much easier in the key music cities (in the US) to find a great, very legitimate and efficient acoustician, but sometimes, I have to almost put acousticians on par with chiropractors...there are some GREAT ones out there that get to the source of the problem, but there are also a good few that never really get to the source of the problems and keep running you in circles, meanwhile you spend loads of money(whether they are good intentioned and ethical or not).

And I have to disagree a little bit about the balance between music and spoken word. I think a good rig is a good rig and will handle 70db's as well as 115(if you choose the right one). I wouldn't have said that 10-15 years ago.

that being said, I agree with tiny, that you may want to go mono in this wide of a room

[Dave Martin]

Originally posted by doug_hti
I feel that (many times) more bang for the buck can be achieved with better boxes setup and flown properly, then with spending 10's of $k's on an acoustician consulting and room treatment(that never turns out to be enough), when no budget is left for a good sounding rig.

I'm not gonna argue with the idea, Doug (since you're far more experianced with live sound then I will ever be), but I do know that a lot of churches have volunteers to do stuff like hanging PA's, and the member who used to be in a local band is responsible for putting the system together...

I've seen PA cabinest hung by ropes, chains, wire left from building speaker cable... They DO need to hire competent people to put design and install teir system, even if it's not an acoustic consultant.

[RobMacki]

Your biggest challenge will be to get the 'board' to agree on anything.
Your next biggest challenge will be to have someone who knows how to mix well for worship. If that will be you then I retract that statement.
Your third biggest challenge will be all the opinions on how it should be and how it should sound from the pastor's daughter who has to do a solo to the pastor's mother who says it is too loud, to the musicians who think nothing sounds good in mono to the person who has been there for 20yrs and says "we can't put those speakers there"
I have seen so much money thrown at church sound systems to have some volunteer ruin the sound. Or worse, some kid who doesn't know the first thing about, well, much of anything really.
Ok I rant.
The change of the room will benefit the worship experience. The folks will feel more together. If at all possible check for slap back and try to treat it and put that into the budget. You get a drummer in a parallel box with hard surface and he will lose the beat and it will kill the worship. I don't know if you specified a budget or not but keep it as simple as possible. You can have quality and simple too. If you go for treatment for the room I'd suggest to keep the ceiling reflective. This will add to the worship experience IMHO. Trust me.
If you are looking into new equpment check out EAW speakers and Spirit console. (that will go over well with the board too) Although you don't need to replace the A&H. I agree with mono too. Get a RTA to tune up the room. (speakers) Just my .02 mites.

[doug_hti]

Originally posted by Dave Martin
I'm not gonna argue with the idea, Doug (since you're far more experianced with live sound then I will ever be), but I do know that a lot of churches have volunteers to do stuff like hanging PA's, and the member who used to be in a local band is responsible for putting the system together...

I've seen PA cabinest hung by ropes, chains, wire left from building speaker cable... They DO need to hire competent people to put design and install teir system, even if it's not an acoustic consultant.

I DEFINATELY was not recommending the DIY route or self installs, but maybe to not dismiss the idea of getting a great PA in there and have a SMAART guy bring out the potential of it, then address the room if need be. They may be suprised with how good it sounds, and find the real reflections of the new rig.

And if you choose a company like EAW (which i'm also a big fan of with Rob), you can utilize their ASG department, and they will tell you the ideal locations and angles to install the boxes. EAW has really dialed in their settings of how to get the most out of their boxes. And if you have a great SMAART person to dial it home, your in business.

[Dave Martin]

What Doug said. EAW cabs, a rigger to hang them and you're set.

[tINY]

Another thing that is gonna get tricky is the aspect ratio of the room once you consider the stage/altar. If it's thrust into the room 20 feet (which isn't much) then it'll be 30' to the back in the center and 55' to the corners. It will be hard to get good coverage without putting a lot of sound energy onto those hard plaster walls.

Look at the JBL website for a good overview of sound reinforcement ...

http://www.jblpro.com/pub/manuals/pssdm_1.pdf
http://www.jblpro.com/pub/manuals/pssdm_2.pdf
http://www.jblpro.com/pages/tech_lib.htm




-tINY

[Brad Lunde]

G Monkey:

The rules of the game in SR seem to boil down to a PA avoiding sending direct sound against hard reflective surfaces (tile/marble floors, brick walls, wood seats, hard plaster ceilings). The objective is to send direct sound only to where the listeners are and nowhere else. One of the ways to envison this is to imagine the speakers as "flashlights" that must shine down on ONLY were the listeners are. Anything extra is wasted and becomes the source of most live PA problems [reflections, bounce, echo].

Modern PA's in ambient (reflective) spaces use defined coverage horns, the larger and better ones maintaining their stated pattern at wider bandwidths. A 90 x40 Constant directivity horn covers 90 horizontal, 40 vertical from 1 to 1.5K to 8K or so. With a properly scaled floor plan, pen and onion paper in hand, you can draw out the angles on the onion paper and move it around over the floor plan from the speaker location and get some idea of where the speaker must be and how it must be aimed to cover ONLY what you want. If the 90x40 horn spills direct audio on tons of hard surfaces close to the speaker location, you try a 60x40. If that's too wide, you try a 40x20. Usually it requires some combination of horns to get defined coverage for a complete room with minimum spill onto walls. A 40x20 for the back of the room (a long throw horn), 60x40's for the middle/front or 90x40's for the "closer to the PA" areas. Its a trick to match all these multiple coverage horns up so they cover evenly. This is where a pro can make a huge difference in the end result: its experience+art+science!

You say you have a carpeted floor. This is good: a terrazo floor, wood floor or tile floor is a tremendous relector of sound and always causes a mess. Most churches that go this route for esthetics sooner or later hire a sound designer that tells them to cover it up with carpet! You say you have brick walls, this is bad. You must keep direct sound OFF those walls (or be forced to treat them with acoustic absorbers). A well damped room is forgiving and cheap PAs can work there; an all hard surface room is near impossible even with the largest budget and the best of technology.

All the better companies, JBL, EV, EAW, OAP, Renkus Heinz, etc all have defined coverage horns that are pretty good from 800hz to 10K or so. In horns, horn mouth size dictates low frequency pattern control limit. If its a physically small dimension horn, the pattern control falls apart (widens) at the lower freq's. A physically larger mouth horn [ugly!] can maintain pattern to as low as 800Hz. If you want pattern control to 400Hz, the horn is huge (remember the Community Leviathan?). All horns get narrower and narrower in dispersion above 10K. Bass bins have horrible pattern control no matter what they tell you, unless the bins are actually low freq horns and also have a very large mouth (many feet wide!). These v.large horns control pattern great, but look like hell and almost nobody is willing to look at a what appears to be a construction project hanging over the alter.

Both low freq pattern control and very high freq pattern control is a physics thing you CANNOT get around no matter what the spec sheet says. Many spec sheets in PA are pure marketing........ so buyer beware. This is why a quality sound contractor can cost more initially but save thousands over time.

There is newer pattern control technology that uses DSP in commination with the speakers to make an "array" of speakers behave like a single element to maintain pattern to lower frequencies. This technology is pretty expensive and complex and well beyond the DIY. But a skilled sound contractor can do it and it is the where the art of SR is going now.

Some sellers and manuf pitch direct radiators into ambient spaces under the idea that if you provide a lot of drive units at lower output levels in ambient spaces, you can get audio into the room without "exciting" the extensive reflective surfaces. This is still very controversial because one of the most visible proponents of this is Bose, who is using 4" drive units (with near zero inherent pattern control). If you need only music through the PA, direct radiators can work well. If you need speech, its not very good.

If you use a combination of direct PA and distributed/direct radiator system (horn cluster up front and ceiling speakers in back of the room) you invite sync/delay problems in even modest size rooms.

Direct sound should be 12dB above reflected sound to be understood by most folks. This becomes very important in speech, less so in music. Its common to have the music director want a reflective room (boy all that reverb sounds great!), exactly what destroys clarity in speech! Easier to add a reverb to the music in the PA than to get rid of reverb in the room on speech.

Sorry for the v.long post!
Brad