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[Martin Matthews]

I'm in the position many people seem to end up in.  I have inherited the job of sound engineering (feels wrong to glorify what I do with that term yet!) a small church.  I'm learning loads and plan to keep doing that so that I am ready to recommend a few changes in January when our renovations are done.  I'll keep most of my questions until I have read the back posts here as the answers are probably in there somewhere with one exception...

It seems to me that a narrow horizontal dispersion field would minimise both reflections from the solid stone walls (thankfully the ceiling is fairly high and both it and the floor are fairly non-reflective) and feedback from the preacher's mic front and centre.

Having read a book on sound engineering for live performances I am still far from an expert so I'd like someone to point out where I am going wrong in what seems best to me.  I must be going wrong because it is so hard to find the kit I would need to do what I want so no one else is doing it!  I have attached a drawing of the setup I envisage as working best.  It's sort of to scale.

The red circles are mics with the front trio for preacher and so on.  The oval is the drum kit and rectangle is keyboard.  I picture two foldback monitors between instruments and the front three mics and 90 degree dispersion means they can easily cover the guitar and bass either side with little risk to the three front mics and not too much to the cardioid mics if they are placed properly.

It seems to me that using narrow dispersion main speakers as far forward and to the side as possible I can keep the main HF sound away from both walls and the three front mics (I can use 90 degree dispersion and keep away from the musicians and walls but not those front three mics).  I was hoping for 50 degree but even finding 60 degree outside of stack system components has been a challenge.  Placing them in the corner should minimise any out of synch reflections from the nearby walls.

That leaves the two questions:

• Is my thinking on narrow dispersion being potentially helpful for this system in keeping the bulk of the main PA system sound away from those three mics?
• What speakers offer the narrowest dispersion for a reasonable price?

I think I will need 120dBA maximum SPL although that's only for youth concerts not services where I suspect even 90dBA would do.  The other changes would probably include an Allen & Heath ZED436 or similar with a individual power amps near the speakers.   May try to make do with existing foldback but that decision can be made once the main PA is there as the monitor and slave are just about OK.  DI boxes and a couple of multi-cores complete the picture.  No budget in mind as such (the cash is available to do this professionally but as ever what we don't spend on sound can be used elsewhere - perhaps more wisely).  Seems to me I can get decent 90 degree dispersion speakers with enough volume for £300-600 ($450-$900) each although our existing ones may well do once I fix the cabling which is currently really messed up.  If narrow dispersion helped the sound I guess we might be willing to double the top price but I'd rather not.

Sorry that went on so long but hopefully that's clear.  If not ask and thanks in advance for any help even if it is to point out that I am wrong.

[g'bye, Dick Rees]

Martin....

Welcome.

You are at the start of a long road.  How quickly you get to feeling familiar and competent sort of depends on how much information you can provide those wishing to assist you and keeping an open mind while attempting to sift through the various responses you'll get.  As of now you have given a general over-view of your situation, objectives and experience.  You'll be asked to clarify many points along the way.  The more specific you can be, the better the answers (and opinions) will be in return.  Here are some questions for you to begin:

1.  What are the exact dimensions of the room?
2.  What speakers do you have at the moment?
3.  Are the aims presented those of the congregation, a committee, or just your own?
4.  What processing (if any) do you have now, especially EQ (graphic, parametric, FBX)?
5.  Are there any aesthetic limitations or requirements affecting possible speaker placement?

These are just a few to begin.  Good luck. 

[Tom Young]

It seems to me that using narrow dispersion main speakers as far forward and to the side as possible I can keep the main HF sound away from both walls and the three front mics (I can use 90 degree dispersion and keep away from the musicians and walls but not those front three mics).  I was hoping for 50 degree but even finding 60 degree outside of stack system components has been a challenge.  Placing them in the corner should minimise any out of synch reflections from the nearby walls.

That leaves the two questions:

• Is my thinking on narrow dispersion being potentially helpful for this system in keeping the bulk of the main PA system sound away from those three mics?
• What speakers offer the narrowest dispersion for a reasonable price?

I think I will need 120dBA maximum SPL although that's only for youth concerts not services where I suspect even 90dBA would do.  The other changes would probably include an Allen & Heath ZED436 or similar with a individual power amps near the speakers.   May try to make do with existing foldback but that decision can be made once the main PA is there as the monitor and slave are just about OK.  DI boxes and a couple of multi-cores complete the picture.  No budget in mind as such (the cash is available to do this professionally but as ever what we don't spend on sound can be used elsewhere - perhaps more wisely).  Seems to me I can get decent 90 degree dispersion speakers with enough volume for £300-600 ($450-$900) each although our existing ones may well do once I fix the cabling which is currently really messed up.  If narrow dispersion helped the sound I guess we might be willing to double the top price but I'd rather not.

Good idea to read old threads. But I do not recall one which addresses your primary inquiry.

A few comments/questions:

You state that you may need 120dBA and for youth concerts. You will need subwoofers for this.

What you refer to as a "stack system" is more commonly referred to as a "point source system" and each ldspkr is usually trapezoid shaped and can be arrayed side-by-side and/or top-to-bottom.

Is what you have been looking into a line array system ?

Are you planning to fly (suspend) the new system ?

Is the system going to be stereo or mono ?

Why are the ldspkrs so far back ?

Can they be moved forward so as to not be behind the front microphones ?

How would you describe the acoustics of this space ?

How many seats ?

What type of microphone does the pastor use ?

A partial answer to your question and concerns:

Wall reflections from loudspeakers are less destructive (typically) than those from the ceiling. Picture (or draw) the energy from a ldspkr projecting onto the wall and its reflection coming back out and combining with the direct sound. There is not that much of a time (arrival) difference at the listeners' ears. So much of the energy is combined with the direct sound constructively and discrete reflections are not heard. This assumes that the ldspkrs are close to the walls. If these ldsprks were tilted down a bit, much of this energy is absorbed by the seats and audience, as well.

Now picture the sound going up and reflecting off the ceiling and then combining down at seated height with the direct sound. Much more timing offset, right ? We (humans) generally do not perceive reflections until they are 30mS (milliseconds) or greater behind the direct sound. They also have to be close to the same level as the direct sound in order to be noticeable and/or interfere to a degree that we would be concerned with.

Another reality to be aware of is that the specified coverage angles are really only "nominal". Below the frequency where the HF horn has pattern control there is less and less controlled coverage as you go down in frequency. A well-designed fullrange ldspkr has a large enough HF horn to control the pattern down to (at least) the crossover point. Many ldspkrs do not have a HF horn large enough to do this. An additional reality is that at higher frequencies the sound begins to beam. Few HF horns are designed to spread upper frequencies out.

So the underlying point here is to not take the specified coverage angles as the "gospel", although we do use them as general guidelines at higher frqeuencies.

The coverage issues above also come into play as far as how the ldspkrs will impact those at the front of your platform and the potential for feedback. In your drawing the coverage angle skirts, but misses, the front microphones. But at those frequencies below where there is pattern control the coverage angle increases and these mcirophones will be in the coverage of the ldspkrs. Not good.

I should note that undertaking this task is quite ambitious. Aside from selecting the best ldspkrs you will need to ensure that they are mounted at the best positions and rigged safely. Then you have to measure the installed ldspkrs and optimize them with equalization, high-pass (and low pass if subs are in the system) filters, delay and dynamics (level) protection.

More later. I'll wait to see your answers to my (and Dick's) questions.

[Brad Weber]

Martin, it's great to see someone thinking about these things ahead of time!

To add to Tom's comments, you have the the right general idea regarding coverage angles but the problem with your concept and sketch, or more specifically where they diverge a bit from the real world, is two fold.  First, the nominal pattern of a speaker is simply where it's output is 6dB down compared to the on-axis response.  A nominal 50 degree speaker may be 6dB down at 25 degrees off axis, but at 45 degrees off axis it could be 20dB down or still 6dB down or even just 1 or 2 dB down.  The same at any other angle.  Having a 50 degree nominal pattern does not mean that there is no sound emanating outside that 50 degree 'cone', only that it is likely to be at some lower level. 

Related to that, the actual pattern of most speakers varies with frequency, sometimes significantly.  Speakers also tend to have less directional behavior at lower frequencies, and not just very low but well into the speech range.  The typical horn of a typical compact speaker may start to lose directional control well above 1,000Hz and for a full range speaker to maintain an true 50 degree pattern even down to 800Hz or 500Hz would usually require a physically rather large horn.

Put these together and the problem is that between distance losses and angular losses, at some frequencies the microphones may be receiving levels greater than what the audience receives.  And because the speakers are not that far off-axis for the microphones, the microphones themselves will provide limited rejection of the sound.  That is typically a recipe for feedback problems.

So while you are right that reducing the energy from the speakers hitting the walls would generally be desirable, there are also good reason why it is also typically desirable to locate the speakers in front of the microphones.


To highlight Dick's comments regarding it being a long road, good sound system design is not something one can learn all about by reading a book or two regardless of how good the books.  Between Dick, Tom and myself there is probably somewhere close to 100 years of sound system design experience, yet we are all still learning new things all the time. 

[g'bye, Dick Rees]

Between Dick, Tom and myself there is probably somewhere close to 100 years of sound system design experience, yet we are all still learning new things all the time.

Amen, brother!!!!

Just would like to add a bit:

As pointed out, reflections are a three-dimensional phenomenon requiring you to think also of the positioning of the speaker(s) in three dimensions.  The subject of "to fly or not to fly" will inevitably arise since it is often the case that equal coverage of a space and focusing the largest percentage of sound directly on the listeners dictates an elevated and centered position.

You should also keep in mind that there will be reflections no matter what you do.  Whether they are early or late reflections makes a difference, but the over-riding principle in this regard is that of "critical distance".  This is something you should research and take to heart.

More later, most likely. 

[Martin Matthews]

To highlight Dick's comments regarding it being a long road, good sound system design is not something one can learn all about by reading a book or two regardless of how good the books. 

I'll try to answer everyone's questions in one post so this may take a while.  Meanwhile though on the subject of this field of knowledge the big impact on me is that it is a monster.  I'm a pretty quick study and have picked up fairly advanced ability in a range of IT-based areas from working on computers and networks to Web-based programming.   Most of the time it puzzles me that anyone could do a whole degree in the subject but with sound engineering the opposite seems true - how could even a degree cover all this stuff given the math, science and just practical experience required.  So to the questions:

1.  What are the exact dimensions of the room?

13.5 long by 10.5 metres wide with three rows of raised pews at the back which take up the 3 metres shown ont he drawing.  There is an alcove behind the musicians which I have not been able to measure as it currtently has no floor as we wait for the baptistry to be delivered!  Height is probably 5-6 metres with a false ceiling (will try to confirm today if we have access).  Walls are painted stone with windows set back giving a few 45 degree 18 inch deep angles to spread the sound around a bit.  Floor will be carpeted wood but with lots of very solid beams to reduce resonance nicely.

2.  What speakers do you have at the moment?

Not sure of the models as they are in storage ATM but Phonics with 15" bass drivers.

3.  Are the aims presented those of the congregation, a committee, or just your own?

Mine but I have been priming the leaders with my thoughts and they are happy to be advised.  We doi intend to bring in professional advice and help but I like to understand what that type of person is saying from my own knowledge.  If only to judge their competence with a few well-aimed questions.

4.  What processing (if any) do you have now, especially EQ (graphic, parametric, FBX)?

Nothing now so I have no experience with this area.  The current mixer has simple three band EQ on inputs plus 8-band on output but the quality degrades so badly I don't use it.

5.  Are there any aesthetic limitations or requirements affecting possible speaker placement?

Suspended speakers below four metres up would obscure the main LCD projector but otherwise sounds good.  Leadership is at least partly keen on flat panel speakers.  I can't think of any other limitations.

You state that you may need 120dBA and for youth concerts. You will need subwoofers for this.

Thanks for confirming my thoughts on this although this can come later if necessary.

Is the system going to be stereo or mono ?

I have no fixed thoughts on this.  Previously the musicians were crammed into one corner and the sound quality has been awful so any attempt to spread the soudn stage failed.  With the musicians spread across the front I did hope to pan each instrument to provide some separation but I haven't spent much time thinking about that.

Why are the ldspkrs so far back ?

I think largely because I hadn't thought of suspending them!  I am generally aware of the inverse square rule and therefore now that the sound level will drop most quickly nearer to the speakers.  By moving them back I can reduce the difference in level from the front of the congregation to the back (picture attached although it does assume a point source which I am guessing the horns at least will not be).  Aesthetics was part of it but suspended speakers would fix that.  Would I then need a delay on them or are the distances too small to worry about?

Can they be moved forward so as to not be behind the front microphones ?

Yes.  There are even bracing bars (narrow steel struts maybe as little as an inch in width) in various useful places for suspending speakers and lights.

How many seats ?

None at the moment!  The pews at the back seat maybe 45-50 leaving the 10.5x10.5 metre area for flexible use.  As the work is still being done I can't be sure but most of the time I expect 80 semi-permanent seats in that area with another 40-50 added as needed.

What type of microphone does the pastor use ?

ATM an Audio Technica UHF radio mic but I think it is about to become illegal under UK law next year so will probably be replaced.  Currently there is also a fixed condenser mic (unknown model) which will either be replaced or supplemented with another for the total of three.  I'd like the two fixed ones to double as extra mics for vocals at times.

All three will be muted when music plays unless we get a preacher who is a bit more involved with the music than normal.

Responses to other comments so far

Obviously many thanks for the tips already given.

Reflections from the walls may be more of an issue due to their nature but once it's done I will try and find out.  Wall hangings are unlikely to be an option judging by the reaction to that thought initially.

I am aware of the very different directional characteristics of high and low frequencies.  In fact it was that lightbulb turning on which convinced me I was understanding some of what I was reading!  I was able to experiment with our temporary setup (in a hotel function room nearby) when the muscians complained they could not hear the keyboard or female vocals.  We had set up slightly differently and they were just outside of the effective beam of the higher frequencies but still getting the lower ones clearly.  It was that which started me wondering about narrow dispersion and how it might help.

On early and late reflections that was (I now remember!) another reason for thinking the speakers might benefit from being in the corners.

For information the plan is:

• Steal as much opinion from people such as yourselves up to mid-December
• Set up the old system again but with proper cabling (they were using unbalanced cables over 20-25 metres and have maybe even more from powered mixer to speakers) to see how much that helps
• Visit a convention/show in January to look for ideas and more opinion
• Get a couple of people in to advise and then one to set up

My ideas of how it might work are mainly to allow me to understand the basics and will only be used as solutions if the cabling helps enough to say that the sound is good enough without spending on anything other than cabling, mixer and power amps (unlikely but possible).

Thanks again.

Edit (twice): I have uploaded some photos to Picasa showing the inside of the chapel as it stands.  My guess about height was about right - 4metres to where it starts to bend in and another 2 metres to the highest.

https://picasaweb.google.com/110179376277902636292/SCFInternals?authuser=0&authkey=Gv1sRgCJaKguri7NS_xAE&feat=directlink#

The only other update is that one of the reasons for the renovation was to improve flexibility.  Fixed suspended speakers in one location would reduce that.  However, would it be possible to fix a speaker in each top corner (at 4m height) corner and only use two at a time depending on the way the room was being used?  If you have a look at the remaining banked pews and you know that here in Cornwall male voice choirs are as popular as in Wales you can probably see that sometimes the audience might face the opposite direction.

[Ivan Beaver]

There is a lot to address, but here are a couple of thoughts.

Do you REALLY understand how loud 120dB A is?  Think of your LOUD rock bands-AC/DC'Metallica etc-don't get that loud A weighted.  I am assuming some sort of slow/average response time.

Do you need to be louder than them? Do you realise how much hearing damage you will cause?  just something to think about.

In a properly designed system, the levels at the front of the room will be the same as those at the rear of the room.  If the loudspeakers are flown this is possible-using the proper design.  If you place the loudspeakers down low-it will be louder in the front than the rear.

Why do "others" think flat panel speakers are the proper tool?  Or is it the name they like?  If horizontal pattern control is what you need, you will need to look for loudsepeakers that are horn loaded with large horns-at least down through the midrange freq.

I may have missed it, but what sort of budget do you have to work with? And what does it include? Loudspeakers? amps? Processing? install? etc.  that is also going to limit what you can and can't do.

Of course the "correct" answer is to hire somebody who really understands system design and your needs-not just somebody who wants to sell you some gear.

[g'bye, Dick Rees]

Why do "others" think flat panel speakers are the proper tool? 

My guess would be, "because they don't look like speakers".........

[Arnold B. Krueger]

I'm in the position many people seem to end up in.  I have inherited the job of sound engineering (feels wrong to glorify what I do with that term yet!) a small church.  I'm learning loads and plan to keep doing that so that I am ready to recommend a few changes in January when our renovations are done.  I'll keep most of my questions until I have read the back posts here as the answers are probably in there somewhere with one exception...

It seems to me that a narrow horizontal dispersion field would minimise both reflections from the solid stone walls (thankfully the ceiling is fairly high and both it and the floor are fairly non-reflective) and feedback from the preacher's mic front and centre.

Good insight.

If you want to see some speakers that were designed for rooms like the one you are in, check out Electrovoice's EVI series:http://www.electrovoice.com/family.php?id=39

I'd like to encourage you by sayng that you've got a pretty nice room to work with. It reminds me of a room in my church we call the chapel, and its probably the best sounding room in the whole building except maybe our youth room which is pretty special.

I agree with those who suggest that your SPL goals are probably over the top. Good stewardship includes the ears of your congregation, and even just peaks of 102 dB SPL are probably damaging to them. A reasonable goal is 90 dB long term average for the loudest segments of a selected song or two in your worship service. With A-weightnig which might allow up to 110 dB for very short term peaks.

[Brad Weber]

For information the plan is:

• Steal as much opinion from people such as yourselves up to mid-December
• Set up the old system again but with proper cabling (they were using unbalanced cables over 20-25 metres and have maybe even more from powered mixer to speakers) to see how much that helps
• Visit a convention/show in January to look for ideas and more opinion
• Get a couple of people in to advise and then one to set up

My ideas of how it might work are mainly to allow me to understand the basics and will only be used as solutions if the cabling helps enough to say that the sound is good enough without spending on anything other than cabling, mixer and power amps (unlikely but possible).

The only other update is that one of the reasons for the renovation was to improve flexibility.  Fixed suspended speakers in one location would reduce that.  However, would it be possible to fix a speaker in each top corner (at 4m height) corner and only use two at a time depending on the way the room was being used?  If you have a look at the remaining banked pews and you know that here in Cornwall male voice choirs are as popular as in Wales you can probably see that sometimes the audience might face the opposite direction.

This is where you may need to change your plan.  Step 1 should be to identify the goals for and limitations on the system.  Put together a document that in simple terms describes what would define a desired or acceptable result.  This should identify what the system needs to do, what it needs to not do, what you wish it could do, how much you want to spend, etc. all in language that everyone involved can understand.  It should be something those involved in the church can review and eventually get everyone to 'buy into'.  Once you have that then you will have a good definition of the actual the situation and can start looking at potential solutions based on that information.

I'm in the position many people seem to end up in.  I have inherited the job of sound engineering (feels wrong to glorify what I do with that term yet!) a small church.  I'm learning loads and plan to keep doing that so that I am ready to recommend a few changes in January when our renovations are done.

Another place where your plans should probably change as you probably don't want to wait until the renovation is done, in fact this effort likely should have started back when plans for the renovation started so that it could have been an integral part of the overall renovation.  Unless you already considered and prepared for aspects such as power provisions, cable paths, equipment locations, etc. then instead of being able to work the sound system in as an integral part of the renovation work and the renovated space, you are going to be working around those and possibly redoing work that was just completed.  For example, unless you accounted for power to the proposed amplifier location and cabling paths from the mixer to the amp and from there to the speakers, then that may end up dictating what you do or require opening up newly finished walls.

If the church leadership views the sound system as something like furniture that you add to a completed room and change at will then that is an important consideration and may drive many aspects of the sound system.

Frankly, I do not understand the plan to use the existing system temporarily and then soon put in a new system.  It would be typical, and recommended, to plan for any long term sound system installation as part of the overall renovation so you could address the issues noted above.  I'm also thinking that they would want to use the space once the renovation is complete and not finish one renovation just to start another.  And you may also want to think about timing in terms of realistic time periods to allow, if you wait until the last minute to make equipment, system designer and system installer choices then the decisions on those may end up driven by availability.  You could spend a lot of time narrowing your choice down to particular products only to find them temporarily backordered while good system designers and installers may not be immediately available when you want them.

The simple reality is that based on the pictures you provided and the apparent progress of the renovation, your hands may be tied on many of these issues.  However, knowing that and the potential limitations and conditions it could then apply to any potential systems and its installation are important.  For example, if it is not practical at this point to get power at the speakers or in a place where amplifiers could be housed then powered speakers or your concept of locating the amps nearer the speakers may not be practical.

[ProSoundWeb Community]