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Old 15th November 2009, 10:49 PM   #11
Eva is offline Eva  Spain
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Quote:
Originally Posted by AuroraB View Post
There is a strange misconception by a lot of "PA installers" (quotes are deliberate) that PA is all about large to huge speakers in one end and lot's of power. If this was a band gig, it could be OK, but this surely isn't?
If the main aisle is, say 40 m long, in order for the listener in the rear to have an acceptable level, the poor folks in the front row should wear ear protection. I may be wrong, but if the system you're looking for is speech amplification during services and the likes, you don't need a PA system , - you need sound reinforcement. Not the same task! Using higher sound levels in a highly echoic environment ike a church, will only make the echo and feedback problems even worse.

If this system is not to be used for music PA, you'll be a lot better off using 4-5 ( the more the better) smallish speakers on each side, all mono fed by a 100V amp system. Bandwidth in the order of 100-10k Hz is plenty good enough for a task like this. The whole idea is not to make peoples ears wobble, but to present an acceptable and most uniform level of sound over the actual listening area. If this doesn't make any sense, like e.g. 100V amplifiers, drop me a PM, and I'll respond...
( I'm travelling, - away from home base and may not see direct post in this thread )
NEVER use many small speakers spread over different locations. This is THE #1 MISCONCEPTION and a very bad practice (from the ones that only care about $elling $peaker$) it really makes understanding speech harder (not to mention zero sound quality) because many more delayed copies of the sound are created and overlapped (echo/reverb is multiplied, particularly if they are placed near corners).

A line source is a good solution. Line sources suffer less attenuation with distance and directivity prevents reflections from troublesome surfaces. A vertical line source would prevent floor and ceiling reflections (and most of the echo/reverb). If the speakers comprising the line source have controlled horizontal directivity (or it is controlled in some way), reflections in walls may be avoided resulting in much cleaner sound.
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Last edited by Eva; 15th November 2009 at 10:52 PM.
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Old 16th November 2009, 03:10 AM   #12
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I slept through the sermon this morning, could someone tell me what I missed.

Church is like being on a NYC subway platform -- you'd better know where you're going before you get on.
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Old 16th November 2009, 11:38 AM   #13
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Reflections are certainly the biggest problem. Clap your hands in the empty church and the sound takes about half a second or more to disappear (to my aged ears!). It's great for hymns - reinforces the music but speech is the issue.

As for a cure, cost of dealing with the problem is another one. I may be mistaken, but unlike the American churches, churches in the UK struggle just to make enough money to maintain the buildings. Ours was built in 1120, and is Grade 1 Listed (i.e. special regulations apply to any work we do in it) which makes any job doubly expensive. We may not even be permitted to install a chain of speakers.
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Old 16th November 2009, 08:09 PM   #14
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Bose l1 compact .... i truly think that particular system will not only look good, but sound nice for what your using... its really easy to setup.. you could do it your self really...
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Old 18th November 2009, 01:32 AM   #15
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I'm no expert in church or PA sound, but here are my thoughts.

1. Acoustics

Firstly, try to do as much as you can about the acoustics. Do you have a creative department in the church that might create some banners? These banners hanging across or down the side walls can appear as decoration, feature bible verses, seasonal themes, but actually they are also acoustic treatment. (Also a clever way to sneak it into the budget). You enhance them by having foam behind them so they sit out (the thicker they are, the more they will work into the low midrange).

If you don't have carpet or cushions or padded seats, this will help a great deal in floor to ceiling reflections. Probably best to leave the ceiling.

Treat the wall opposite the front where the sound comes from. Foam is expensive when it's called "acoustic foam," and even expensive when you buy it in a store without any special label. However, it's potentially free when recycled from old couches or foam matresses. I have quite a few bits of foam like that I picked up with acoustics in mind.

These things can be cheap, have an extra benefit and make a bigger difference than the choice in amps!

2. Speakers

Also a great area for DIY. I'd probably look at a DIY speaker with a 15" driver and matching waveguide. Possibly bigger than you were thinking but the larger size gives greater directivity control over a broader range, meaning less reflections. You also get higher efficiency as a bonus. In a decent size vented box you'll get down to 50 Hz and while speech is the priority you'll cover the range needed for music as well.

You might consider Geddes kits, or Pi speakers

3. Amp

There are a lot of good choices here, including a number of affordable options. It's always better to have more power than you need. I have 650watts in my home audio amp! I don't use all of it but it's good to have. Also if you ever hire out your hall for events it can come in handy.

One thing to look for is an amp that powers up and down without thumps, which can come from other components.

4. Mixer

Here you might consider your immediate and longer term needs, as well as uses that might go beyond what is typical. Having more channels is going to come in handy if you hire out your hall. If budget is tight perhaps that's something to consider. Over time it could cover the cost of the system.

5. Installation

Pro cables are easy to solder up. The XLR connections are easy to solder up and allow plenty of room and cover things up nicely. Of course, you want to make sure everything is robust as the end user is not the person soldering the cables.

I can't visualise the space, but some care is needed in placement of the speakers to get the best result. You may want to post some photos.

I'm inclined to think you should start with a main pair of speakers. Considering the length of the hall you may benefit from an additional pair of speakers towards the rear on the side walls. These should have a delay so that they are "in-time" with the main speakers. This prevents making it too loud in the front so the people at the rear can hear. I've seen this done in a large long high reverberant church and it worked fine.

You can do this with a unit like Behringer Ultradrive. It's a digital active crossover, but you can also use it for digital delay. Also it has compressors which you might be a bit sneaky and use with speakers who like to preach a little too loud at times! You can set up filters that start to reduce the volume when the level hits a certain point. Some speakers get a bit too loud to make a point, but you can keep it within reasonable limits without turning the volume slider down! If they complain you can say "hey I didn't change the volume!!!!"

Again, this isn't really my area, but this is how I'd tackle it.
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Old 1st December 2009, 02:22 AM   #16
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1. Bose is crap.

2. Consider the relative distance to the speakers - if the front row is 1ft from the back speakers and the back row is 50 feet from the speakers, you've got a bit of a problem. The simplest solution to this problem would be to put some corner horns on the ceiling in the front of the room. Another option is line arrays, which use a trick of acoustics to decrease the difference in volume between the front and back of the room.

This leaves you with two options - a relatively simple and traditional "speaker in a box", and a more complicated line array. Implementing the former is relatively simple - build the large high-efficiency design of your choice and EQ as necessary. Earl Geddes makes some very well-rated kits, and there are no doubt some freely available plans out there. Alternately, you can buy some commercial speakers - you can get some Tapco Thump 15" powered 2-ways for about $500 that might do the job if all you need is to amplify human speech.

The second option is a lot more complicated - line arrays generally require some rather fiddly design, an active crossover, and multiple amplifiers. The cost is also likely to be higher, though not by as much as you'd think. (There are a few designs for simpler, smaller designs with passive crossovers, but the size of a line array is directly tied to how far you sit from it, and all of these are much too small.) However, if you an pull it off, the result can have some pretty spectacular results.

Regardless of speaker, buy good amplification. Tapco, a Mackie brand, offers very good value for money - not fancy, but generally regarded as well made.

Building an enlarged version of one of the aforementioned similar arrays is also an option, but the operative word here is "enlarged". If you were to get several cartons of 3"-4" fullrange drivers, you could build some whopping enormous line arrays - at least 20' high. If you can find a few cartons of cheap fullrange drivers (such of the NSBs of which I myself have a carton of 30), this could be a very economical option that's also quite simple to build.

Incidentally, soldering the ends on XLR cables is relatively simple. Go buy a spool of good quality cable - shielded Canare Star Quad, for example - and some heavy duty XLR connectors, like Neutrik. You can also buy premanufactured "cable snakes" with multiple XLR connections on two ends of one very long, very heavy cable.
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Old 1st December 2009, 03:09 AM   #17
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I have done an install with these characteristics. My two cents are

1. Bose is crap!
2. Don't 'overcome' the envioronment, 'Use it' Use mono sound, speakers (100Hz to 20K, tweeters don't cost that much). Mount the speakers at the opogee and use the hight to provide a horn load.
3. Test first before buying. Borrow some good 6" two ways, mount them high up and run some music through them, see what happens. It will be the most fun you have had in a church.
4. Make sure you have a three band parametric equalizer in the system, these are great for dealing with feedback nodes.

And the voice from on high sayeth to me.......

Terry
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Last edited by pheonix358; 1st December 2009 at 03:12 AM. Reason: Added 4
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Old 1st December 2009, 03:11 AM   #18
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Originally Posted by pheonix358 View Post
2. Don't 'overcome' the envioronment, 'Use it' Use mono sound, speakers (100Hz to 20K, tweeters don't cost that much). Mount the speakers at the opogee and use the hight to provide a horn load.
I suggested much the same thing.

One note, however - if you're going to be putting the speakers in the high front corners of the room, you'll really be wanting horns. Horns limit dispersion, which prevents high frequency sound from being bounced off the walls and making an echo-y mess. Covering these walls with some sort of cloth might not be a bad idea.
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Old 1st December 2009, 03:23 AM   #19
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Quote:
Originally Posted by Spasticteapot View Post
I suggested much the same thing.

One note, however - if you're going to be putting the speakers in the high front corners of the room, you'll really be wanting horns. Horns limit dispersion, which prevents high frequency sound from being bounced off the walls and making an echo-y mess. Covering these walls with some sort of cloth might not be a bad idea.
Perhaps you missed the point? The ceiling is a church ceiling with a height of 30 metres. If you mount speakers close together pointing downward you end up with point source covering the whole church. Use MTM speakers to get in the order of 92dB, one wave of sound coming from maximum height using the ceiling itself as the horn. Works very well.

Terry
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Old 1st December 2009, 03:33 AM   #20
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An example, just to give you some ideas. Take a 6.5" woofer with good power handling and say 90dB. Put four each in two enclosures. The first woofer gives 90dB, second woofer takes that up to 96dB. The third and fourth woofers double the xmax and power and 8 Ohms. The second box is connected // to the first and gives another 6 dB gain. If tweeters may be required or maybe not, run them in a close array (Morel MDT41 are ideal.) and run them from a separate power amp, the second channel perhaps. Now you can have them off for speech and on when you wish to play angelic music.

Terry
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