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[g'bye, Dick Rees]

Well, I’m actually focusing on trying to understand the logic behind what most people are suggesting here. But I’m not given any explanations here. Instead I’m given maxims like “less speakers the better” without explaining why is it better in this particular case.

You've been "given" enough information to make a decent stab at doing the job.  You cannot be "given" a specific solution for your question without first-hand, on-site consultation.  The principles for implementation are absolute.  The specific implementation depends upon your ability to interpret and apply the principles to your specific situation.

At some point, you're going to have to actually sit down and study.  This is a forum for dispensing and sharing knowledge and experience.  It is not somewhere to have people do your work for you and spoon feed you what you think you want to hear or to validate your misconceptions.

Good luck.  You're on your own no matter how many suggestions and opinions you may receive on the Interweb.

PS...

Just as you can't tell us exactly how the room sounds (other than a gross statement characterizing it as "live"), we can't tell you exactly where to put things to make it sound the best.  We can only tell you the applicable principles.

We can hand you the hammer.  We can't drive the nail.

[Stan Chigintsev]

Dick,
Just to clarify, this is where I got the “speakers at corners” idea from:

John Halliburton  said:
"If so, one pair of speakers at each corner, aimed out to maximize the coverage hopefully with no overlap".

Tim Perry said:
"What would make you think that 2 speakers in stands would be insufficient?"

They didn’t have a chance to explain why. From what I understand, above advices don’t make sense. The link you gave me points at the need for more speakers because critical distance is short in this room...

Just as you can't tell us exactly how the room sounds (other than a gross statement characterizing it as "live"), we can't tell you exactly where to put things to make it sound the best.  We can only tell you the applicable principles.

It sounds somewhat like a school gym with even longer decay.

[Mac Kerr]

Well, I’m actually focusing on trying to understand the logic behind what most people are suggesting here. But I’m not given any explanations here. Instead I’m given maxims like “less speakers the better” without explaining why is it better in this particular case.

I’ve given all the information about the event, including floor plan, available speakers, mics, requirenements to cover whole room, type of performance (speech) etc., etc..  Please, let me know what more information you need – I will gladly provide. If you want money for this advice then I don’t understand why this forum is free and what is the purpose of it at all.   I thought this is place where people can learn, give and get advices, share experience… I guess I was wrong? Looking down with attitude like “I won’t tell you the secret, newbie” does not make anyone look professional, if that matters to anyone.

To start with you could provide a better drawing.

I can't tell what you are trying to show, but if the blobs in the corners are speakers facing into the center of the room, there is probably no worse place to put them. Try using an x to define the speaker position, and an arrow to define the direction it is pointing. You should be trying to cover the audience area with as little overlap between speakers as possible. If the primary performance area is in that area defined by the columns the speakers should face out from there, and you will probably need some delayed speakers halfway down the long dimension to continue the coverage farther into the room. As a rule of thumb, I define a normal single box speaker of 60x40 or 90x40 as being able to reach about 2.5x the height it's flown at. You want the speakers as high as you can get them (unless you are talking about more than 25'), and angled down at the audience to keep reflections off the walls.

If the talent is really going to walk all over the room there will be other issues that come into play. With delayed speakers relaying the sound down the long dimension of the room it will be increasingly harder for the talent to speak clearly as they hear their own voice coming back at them with a delay. You really need to limit their movement to one end of the room.

Mac

[g'bye, Dick Rees]

Dick,
Just to clarify, this is where I got the “speakers at corners” idea from:

John Halliburton  said:
"If so, one pair of speakers at each corner, aimed out to maximize the coverage hopefully with no overlap".

You missed the point.  What John said was this:

"Please clarify-The area defined by poles 5, 6,7, and 8 will be a stage?

If so, one pair of speakers at each corner, aimed out to maximize the coverage hopefully with no overlap."

Clearly, he is defining the center of the room in this case as "the stage", and if it is "the stage", he is suggesting placing the speakers  at the corners of the stage, not in the corners of the room.  The key is "aimed out". 

Pay very close attention to what Mac says.  It's pretty much gospel.

[Stan Chigintsev]

You missed the point.  What John said was this:

"Please clarify-The area defined by poles 5, 6,7, and 8 will be a stage?

If so, one pair of speakers at each corner, aimed out to maximize the coverage hopefully with no overlap."

Clearly, he is defining the center of the room in this case as "the stage", and if it is "the stage", he is suggesting placing the speakers  at the corners of the stage, not in the corners of the room.  The key is "aimed out". 

Ok, I can see where I did not express myself clearly. The area defined by columns is the area where more people will be, because there will be a small stage somewhere by the columns, so people will be more concentrated by that general area. But actually people will be walking around the whole room and they should be able to hear everything clearly in any point of the room. In other words, the whole room must be covered, but area defined by the columns is what needs to be covered even better.

I can't tell what you are trying to show, but if the blobs in the corners are speakers facing into the center of the room, there is probably no worse place to put them.

Basically, speaker #1 facing #2, speaker #3 facing #4,  speaker #9 facing #10. Speakers 5,6,7,8 aimed at center of the “square” defined by those columns. Speakers can’t face out of that area because actually more people will be inside of that area. I was going to lower level of the 5,6,7,8 comparing to the rest of the speakers but to have them for providing critical distance for that area. And I wasn’t sure if I should delay this group 5,6,7,8 against the rest.   OR maybe delaying 5,6,7,8,9,10.

[g'bye, Dick Rees]

Ok, I can see where I did not express myself clearly. The area defined by columns is the area where more people will be, because there will be a small stage somewhere by the columns, so people will be more concentrated by that general area. But actually people will be walking around the whole room and they should be able to hear everything clearly in any point of the room. In other words, the whole room must be covered, but area defined by the columns is what needs to be covered even better.

Basically, speaker #1 facing #2, speaker #3 facing #4,  speaker #9 facing #10. Speakers 5,6,7,8 aimed at center of the “square” defined by those columns. Speakers can’t face out of that area because actually more people will be inside of that area. I was going to lower level of the 5,6,7,8 comparing to the rest of the speakers but to have them for providing critical distance for that area. And I wasn’t sure if I should delay this group 5,6,7,8 against the rest.   OR maybe delaying 5,6,7,8,9,10.

Your diagrammed set up has many drawbacks.  You'll certainly put out a lot of sound into the space.  How it's going to sound is debatable, but smart money looks for another setup. 

It's very common for folks to post their ideas here looking for validation.  I don't think your design is going to get many votes.  You're going to have to prioritize your coverage areas, realizing that in a highly reverberative space there will always be areas which are "not as good" as the best area of coverage.  For the last time, the more speakers you put in there, the more reverberation there will be.  You should "dial it down" a notch concentrating first on the most important area.  Pointing speakers at each other is just a recipe for defeat.  Avoid that at all costs.

You estimate an RT60 of 4 seconds, but you don't say at what frequency(s).  You may have missed the mention of eliminating the most part of the sound outside of the critical range for speech.  It is entirely possible that the length of the reverberation considering only the "telephone" frequencies can be significantly reduced and intelligibility increased by using high-pass filtering on the mic(s) and judicious use of PEQ over the entire system output.

Again, I would encourage you to study up on what you CAN do within the space first, then think about how to do it with your speakers. 

Speaker height and aiming (tilters).

HPF and EQ.

Good luck.  I'm done.

[Ray Aberle]

Ok, I can see where I did not express myself clearly. The area defined by columns is the area where more people will be, because there will be a small stage somewhere by the columns, so people will be more concentrated by that general area. But actually people will be walking around the whole room and they should be able to hear everything clearly in any point of the room. In other words, the whole room must be covered, but area defined by the columns is what needs to be covered even better.

Basically, speaker #1 facing #2, speaker #3 facing #4,  speaker #9 facing #10. Speakers 5,6,7,8 aimed at center of the “square” defined by those columns. Speakers can’t face out of that area because actually more people will be inside of that area. I was going to lower level of the 5,6,7,8 comparing to the rest of the speakers but to have them for providing critical distance for that area. And I wasn’t sure if I should delay this group 5,6,7,8 against the rest.   OR maybe delaying 5,6,7,8,9,10.

Just rent a bunch of IEMs and send everyone a customized mix.

OK, since that's not realistic, as the esteemed Mr. Rees has pointed out, neither will adding more and more speakers to the mix. Remember, of course, the the people on the stage are going to be higher then everyone else in the room-- so presuming that you get the corner speakers up high enough, they're going to pick up a good amount of the signal from those speakers! Four corners of main room, maybe two more each wall facing directly towards the stage, keep those last two on an aux so you can adjust them separately from the rest of the mix, and call it a day. Or put four speakers on the corners of the "stage" and run two more further down the room with a suitable delay.

... or hire someone who has the experience and appropriate equipment to do this right. Even if it's just an A1 who can guide you in the system design and deployment-- there is a limit to what we can offer over the interwebz. You have received a large amount of very valuable advice from people with a helluva lot more experience then you or I.

-Ray

[Jim Thorn]

Stan,

This setup reminds me of one I had to do for an indoor swim meet.  My best bet was to space 10 speakers around the perimeter of the pool so that nobody was very far from the nearest speaker.  Although the reverb time was horrible, most of the participants were in areas where the direct sound from the nearest speaker was louder than the reverb, and none of the speakers had to be very loud.

Most of the other guys are advising you based on a conventional stage-to-audience geometry for a musical performance, and the principles they mention are sound, but I suspect that your situation is a candidate for a distributed system.  I’m a little surprised that nobody has mentioned it yet.  The idea is to spread speakers out so that each speaker has its own section of coverage, with minimal overlap between speakers.  No delays are involved.  In a distributed system, symmetry is your friend – when you transition from one speaker’s coverage area into another’s, you are equidistant from the two speakers, so there is minimal comb-filtering.  (There will always be some, but the symmetry helps to minimize it.)

If I were setting this up, my first effort would be to put five speakers along each of the 140-foot walls, facing directly across the room.  I’d put the end speakers about 20 feet in from the corner, and put about 25 feet between speakers.  In the interest of symmetry, I would have all speakers producing identical levels, rather than trying to emphasize the prime audience area.  Even in the “stage” area, I would have the speakers against the wall.  If the system is equalized to be feedback resistant in other parts of the room, it will be equally feedback resistant in the stage area.  This setup would put cable runs along the baseboards for minimal trip hazard, and maintain the symmetry of coverage areas.  If you hear too much of that “Darth Vader” sound of comb filtering as you walk down the long centerline of the room,  space the speakers farther apart.  But check that you don’t lose too much intelligibility when you walk between speakers near the long walls.  Your best spacing will be determined by the compromise between coverage near the walls and comb filtering near the centerline.  You may even find that you can eliminate two of the speakers if you have to increase the spacing.

As Dick Rees said, the reverb is likely worst at low frequencies, so reducing low midrange will greatly improve intelligibility.  And the advice to get speakers high and tilt them down is always a good idea, as long as you can safely do it.

I hope that your MCs come to you with good mic technique, but you will still have to be vigilant about describing good mic technique to EVERY presenter who will be using a microphone, and do so before show time – you can’t really fix it mid show!

If you have the equalizers to do so, I think you should equalize the Peaveys and the JBLs separately to make them sound as similar as possible.  Based on my experience at the swim meet, I advise you to be ready to adjust EQ on the fly – what sounded good in a silent natatorium was NOT very intelligible in the presence of crowd noise.  I had to carefully re-adjust a couple of octaves of midrange (1k to 4k) upward at meet time.  Later, in a silent room again, that sounded pretty nasty, but it was EXACTLY what was needed during the event.

I believe you do understand the concept of critical distance, and your comment about sports arenas is well taken.  Each cluster has an assigned area, with minimal overlap into adjoining areas, and each cluster, in its area, increases the ratio of direct to reflected sound.

I hope this post is of some help to you.  I believe that if you have an understanding of key concepts, such as the importance of the ratio of direct to reflected sound, and the occurrence of comb filtering as a result of hearing two identical signals of similar levels at different times, then you can experiment with setups to find your own best compromise.  The theoretical knowledge will keep you from pursuing blind alleys.  The best advice I can give is to walk through the entire area with music playing, and listen for the problems that theory says you will find.  Adjust the setup to address the problems, and walk again.  That will take you a long way.

Best Wishes,
Jim Thorn

Hi guys! I need some advice here.

We will be providing sound for an event. Please see a rough sketch of the floor plan (sorry for this ugly sketch :-) ). This is going to be for speech only (no music). The room is EXTREMELY LIVE with concrete walls… Area to be covered is 140 by 80 ft, but actual length of the room is aprox 200 ft, however there’s a kind of a partial plastic wall beyond the 140 ft mark.  Blue dots are the columns. Red are speaker positions as I see them.

Whole area must be covered with speech clearly heard in any point of the room as seen on image. No seats, people will be walking around. MCs will be walking with wireless mics. There will be some stage surrounded by the columns, that’s why I want to place some of the speakers around that area specifically. Only pole-mounted speakers are available. 10 cabs total.

My questions are:
1. Would you agree with proposed speaker placement positions? How would you place them?
2. DO I NEED TO DELAY the group of cabs 5,6,7,8 against group 1,2,3,4 ?  Any other delay scenarios? Or no delay needed?

Thanks!

[g'bye, Dick Rees]

Jim...

Some good points and well said.  But there are still a lot of "catches" stated or implied by the OP:

We don't really know the size of the central columns and what effect they might have on the sound field as far as blocking/reflections.

The OP has a limited number of mis-matched, not really appropriate speakers.

While there would appear to be speaker stands available, we don't know how high they can safely get.  Likewise we do not know if the tilting option is available for aiming.

I do agree that a distributed system is likely the better bet here.  It's the old Bovine Directional Conundrum (BDC).  50 cows grazing in a pasture all facing the same direction.  Which direction are they facing? 

Down.

If you want the most even, effective coverage over such an area with a minimum of destructive reverberation, using 50-60 evenly spaced speakers equidistant from the largest number of listeners, downward facing "ceiling" speakers would be the way to go...in theory.  You can't do that for a one-off.

Alternatively, a center cluster of four 90 degree cabinets mounted exactly in the center of the space facing outward in a ring and angled properly down would place the largest number of people equidistant from them...and in what the OP says is the critical listening area.  I'd think 15 to 20 feet up with the appropriate tilt would be  a good bet.

Any "fill" needed for the outer corners or to cover any shadows behind the columns could be addressed with some smaller boxes on delays.  And as you mentioned, as many channels of EQ as possible.

I have been holding back on the distributed system or delay ring recommendations for the obvious reasons.  Distributed is not within the realm of possibility here and a center cluster with outer ring delay fills may be hard to "sell" to the promoter and/or require more task-specific gear and ability/experience than the OP has available.

I have done a few community freebies in such "concrete caverns" and have found that the best way for all concerned is to communicate to the promoters the practical limitations of doing sound in such a space.  I usually put up a main pair and a few delays and call it a day.  The rate of return on amount of equipment, time and effort goes down very quickly in situations like this.

But an inexperienced announcer or two can still screw it up royally.

[Lyle Williams]

If the reverb time is really 4s you have got to get that down somehow.  Are there any curtains?  Windows/doors that can be opened?  Floorcoverings?  How many people will be in the room during the event?

[ProSoundWeb Community]