Reverb Time





Thread: Reverb Time


One member of the ChurchSoundcheck Discussion Group wrote to ask for help in how to control
the reverb time in his new church sanctuary. Man, did he get an earful.


From: John Hentschel (Columbia, SC)
Subject: Reverb Times

Gentlemen;

As I think most of you now know the church that I attend is in the very
final stages of completion. Our first service is planned for 3/1/98. I
did a simple test and was really amazed at the results.

I clapped my hands, fairly hard, and it took about 3.5 seconds for the
room to become quiet again. The peak was at about 1.5kHz. Even with my
vast amounts of training, I am quite sure that this is going to be a
problem. I think I am headed for another NEW learning experience. I
could hear that sucker racing around the room. There is a huge amount
of painted sheetrock in this building.

My question is, how excessive would you consider this?

John Hentschel
Ministry Resources

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From: Rob Parpatt (Chilliwack, BC, Canada)
Subject: Re: Reverb Times <"My question is, how excessive would you consider this?">

Is all the carpet, pews/seats, furnishings, etc in place? If all you
have is bare walls & unfinished flooring, you are not getting a real
result.

If you have everything in place and have padded pews/chairs etc., you
have a problem.

In the book "Why Are Church Sound Systems & Acoustics So Confusing?"
written by Joseph De Buglio he states that you should never accept a
building with a reverb time at 200 hertz of less than 1.4 seconds or
greater than 2.3 seconds.... again the same times for 2000 hertz. He
later gives a chart with recommend reverb times depending on style of
worship. Pentecostal type services require 1.2 - 1.5 seconds ....
traditional (Catholic with pipe organ?) requre 1.7 - 2.3 second reverb
times. Of course, everyone else is in the middle somewhere.

Having shorter than 1.2 is not recommended. Greater than 2.45 he
recommends fixing the room as the sound will be very poor for listening
or performances.

Mabe you can give us more info. ie, style of worship, # of seats,
height of ceiling (not that you can change that now), shape of room,
padded or hard pews, placement of speakers (cluster?), etc.

Also, you stated that there is a huge amount of painted sheetrock
(drywall for us canucks)in the building. Are all these surfaces flat?
Is there a large flat wall at the back that is ready to reflect sound
back at the stage? Flat walls reflect sound.


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From: Bob Enlow (Norwalk, OH)
Subject: Re: Reverb Times

Hi John,

The organist and musicians will love it, but I would hate to try to listen
to a sermon in there. I have a real problem with speech intelligibility in
a reverberant environment.

Bob Enlow
RESOUND Co.

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From: John B. Hentschel (Columbia, SC)
Subject: Re: Reverb Times

Rob Parpatt wrote: <"Is all the carpet, pews/seats, furnishings, etc in place? If all you have is bare walls & unfinished flooring, you are not getting a real result."> <"If you have everything in place and have padded pews/chairs etc., you have a problem.">

All the carpet and chairs are in place.

The room shape:
Picture a baseball field - the stage is at home plate, the pulpit about
a third of the way between home and the pitchers mound. The wall behind
the pulpit is flat except for a baptistry opening. Looking out from the
pulpit,(baseball again), envision a wall running between where the
second baseman and the shortstop would play. Ceiling is 24 feet with
center cluster and a boxing hanging on either side of the cluster.
Center cluster is just forward of the pulpit (maybe 8 feet).

One disclaimer, I know some of you folks make your living fixing problems
like this and I'm not trying to wheedle out of spending some money. I
knew this was going to be a problem (the acoustics) and tried to prepare
the appropriate people. The information I get here is primarily for my
own training.

John Hentschel
Ministry Resources

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From: Eric Kleinpaste (Gahanna, OH)
Subject: Reverb Times

John,

This sounds similar to a situation I had about ten years ago
with my church in Florida. It was a PCA church and they were
building a new 1200 seat facility. I was new to the church at
the time and talked to the leadership about what they were
constructing. I told them they needed something soft to absorb
and some diffusion because it was a typical 75'x120' rectangular
sanctuary. They said that there would be something done with
it.

Three weeks prior to opening I walked into it to see what was
happening. There was nothing soft and no diffusion. RT60
greater than 4 seconds. The way I dealt with it was to take the
leadership into the room. I had one of them go to the platform
and the rest stand about 2/3's back in the room. I told the man
on the platform to speak loudly. You could barely understand a
word he said. The rest freaked. They brought in some high
priced consultant to try to deal with it. Due to the late state
of construction, the treatment given looked like the patch that
it was. I would fight with the room for the next two years
before moving here to Columbus, OH.

My suggestion is deal with it *NOW*! Save yourself a lot of
headaches.

Eric Kleinpaste
Karl Road Baptist Church

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From: Jim Brown (Chicago, IL)
Subject: Re: Reverb Times <"My question is, how excessive would you consider this?">

Assuming your brain is well calibrated to the 3.5 second
decay, it isn't at all good news. While a very skilled
audio system designer can get an audio system to work well
for speech, any kind of a live band playing contermporary
music is probably going to be varying degrees of awful
before the sound system is even turned on. And there is
nothing to be done electronically to remove this
reverberation for the live band. The sound system can
amplify the direct sound, making the overall sound much
louder, but is likely to become uncomfortably loud before
overpowering the reverberation. And such an audio system
wouldn't be cheap either!

This very well may be exactly the sort acoustic nightmare
that audio professionals and worship teams at other
churches have been telling you can happen. And the worst
news is that there rarely are inexpensive solutions once
the building is built.

For those of you who don't know me, I run my own small
consulting firm designing sound and video systems for
churches, stadiums, and performance facilities. Although I
don't do acoustic consulting myself, I work regularly with
some of the best in the business, and I often feel like I
know more acoustics than a lot of those passing themselves
off as acoustic consultants (but not the good ones).

If any project I'm working on doesn't already have a good
acoustic consultant involved and needs one, I always make
sure a good one is hired for whatever work is needed to
make things right. In fact, I feel so strongly about
getting the acoustics right that I have been known to tell
clients that if their budget is limited, get the acoustics
right and buy the sound system later when they have the
money!

Friends, acoustics is more important in a church than
almost any physical part of the building (after making sure
that it doesn't fall down and the roof doesn't leak!). If
your congregation is building or remodelling a space and
not getting the acoustics carefully attended to, do what
you have to do to make sure it is. It is a near certainty
that if you don't, you and all of your congregation will
regret it in a very large way. Don't trust it to a church
architect, a contractor, or an organ builder, all of which
have littered the landscape with the ugly corpses of their
false assurances.

If you need help, there are several of us on the list who
can point you to good acoustic and audio system
consultants. It ain't cheap, but it is MUCH less costly
than fixing things after they are built. And the sad thing
is that building it right the first time often costs little
more than the poorly designed mess that is built!

Jim Brown
Audio Systems Group, Inc.

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From: Nehemiah Lacar (Chicago, IL)
Subject: Re: Reverb Times

Amen Jim, Accousticians are one of the most valuable tools for building a
church and it's sound system. "Sound" people and sound system consultants
(unless you're an accoustician) need the valuable insight from acousticians...
insights that we're not educated in. Remember, doing it right the first
time will save alot of problems in the future. If studio designers and
owners frequently require their services, shouldn't we?

God Bless

Nehemiah

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From: Rob Parpatt (Chilliwack, BC, Canada)
Subject: Re: Reverb Times <"Picture a baseball field...">

Well, it sounds like the basic setup is well..., er, sound. I'm trying
to guess where the problem lies.... from your description, I would say
the side walls fan out toward the rear? What about the back wall? Is
that a large flat surface? I'm not going to try and guess at a solution
as I only operate a sound system like you. I'm curious as we have a bit
of a reverb problem as well and our church (seats about 350) sounds very
similar in design (except for the unmentionable speaker setup).

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From: Rob Parpatt (Chilliwack, BC, Canada)
Subject: Re: Reverb Times

Jim Brown wrote: <"Assuming your brain is well calibrated to the 3.5 second decay, it isn't at all good news.">

I was under the impression that you wanted more reverb with the worship
team than you did with the pastor? Am I wrong? Our church is about 85%
contemporary (not quite Pentecostal) with drums, guitar, bass, keyboard,
etc. with the occasional organ & piano service.

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From: Curt Taipale (Taipale Media Systems, Inc.)
Subject: Re: Reverb Times <"Flat walls reflect sound.">

As do concave walls. I'm working on a project now where the church has
insisted on keeping a concave back wall. Instead of being proactive and
allowing us to change the pattern of the wall, we're in damage control
with few options left except to put fuzz all over the wall.

The EASE software modeling I've done and auralization checks I've done
have proven out - even to the client - what our concerns were when we
first opened the plans. The focal point for the 200+ milliseconds
reflection? - just four feet behind the pulpit! They won't need a tape
ministry. If you miss the sermon, just stop by the sanctuary later in
the week and hear it again!

Curt
curt@churchsoundcheck.com

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From: Kevin Kaylor (Palm Bay, FL)
Subject: Re: Reverb Times

I have taken over the responsibilities for the sound and light team at my
church. A newly constructed gym/worship center 75x100 with 30 ft walls
and 40Ft peak has an RT60 of 8.53 seconds!!!!!!! Talk about nightmare.
Someone mentioned K-13 produced by International Cellulose a couple of
months ago so I looked them up. They have a website and we are exploring
the use of their product K-13 fc to be sprayed on the walls from 10ft up.
This product sprayed to a 1" thickness should reduce our reverb time to
2 seconds with no other treatments. Unfortunately we have a beautiful
tongue and groove wooden ceiling that cannot be treated. This project
should cost under $10K. Very reasonable considering about 7500 sf of
surface will be sprayed.

Does anyone have any experiences with this product?

We are also on a tight budget and mistakes have obviously been made. I
am trying to right the ship and get it on course....big endeavor. They
also installed a spherical speaker in the center of the room at the
apex...40' above the floor as their one and only speaker....another
topic altogether! The Sound consultant that sold it at full retail
won't take it back....it works fine!!!

Thanks for listening,

Kevin Kaylor
Sound and Light Team coodinator
Palm Bay Christian Church

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From: Rob Parpatt (Chilliwack, BC, Canada)
Subject: Re: Reverb Times

Curt Taipale wrote: <"I'm working on a project now where the church has insisted on keeping a concave back wall.">

Maybe concave is even worse because the concentrate the sound waves.
For some pictures of what one sound company did in Perry Sound, ON take
a look at http://home.echo-on.net/~jdbsound/parysnd.htm

The round outs on the upper wall looked like a pretty neat solution and
don't look like a band aid treatment.

I don't know this company or the person as I live 2000 miles away, but I
have read his book and have found it useful.

Why does everyone always assume that the architect knows more than sound
people. It is really amazing how some designs try to defy almost every
law of physics.

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From: Jim Brown (Chicago, IL)
Subject: Re: Reverb Times <"I was under the impression that you wanted more reverb with the worship team than you did with the pastor? Am I wrong?">

For contemporary music, I would like to see reverberation
times well under 2 seconds, and preferably in the 1 second
range. The major problem is that the reverberation makes
mush of the rhythm section, especially bass. A good sound
system designer can provide very good speech
intelligibility in a 6 second church with the right
loudspeakers in the right place.

On the other side of things, you don't want the church too
dead, so that congregational singing has some life to it.
It's a tradeoff. And in churches which worship with music
in the European classical tradition, you DO want lots of
reverberation. Composers like Bach wrote their church music
to be played in very reberberant churches, and it doesn't
sound right with less then 4-5 seconds. (Bach also wrote
stuff like the Brandenberg Concerti to be performed in much
smaller and less reberberant spaces, like the drawing room
of some wealthy guy's home, where the RT might typically be
1-2 seconds.)

Jim Brown
Audio Systems Group, Inc.

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From: Russel O'Toole (Romeoville, IL)
Subject: Re: Reverb Times

Sounds like a Roman Catholic Catholic Cathedral to me (:>)!

See Syn-Aud-Con Volume 25 No. 2 Spring 1997 article on using %AlCons as
a Critical Distance Modifier. Basically it states that witha an Rt60 of
3 seconds critical distance becomes about 40'. Max d2 (loudspeaker to
furthest listener) is only 48'. Can you keep your listener's all within
48' feet of the loudspeaker to maintain 10% AlCons or less!

Solutions: *Keep loudspeaker to furthest listener distance as close as possible <48' *Use larger fomat high frequency horns *Keep the amount of low frequency boxes as low as possible to avoid exciting the room *Get some acoustical help to control the acoustics of the room

This is not necessarily in order of importance!

Russel L. O'Toole
AUDIO ELECTRONICS, Inc.

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From: Russel O'Toole (Romeoville, IL)
Subject: Re: Reverb Times

Jim:

I liked to cry when I read your post! (:>)

I can't count how many church building architects we have worked with
that refuse to consider the acoustical nightmares they are creating for
their clients and when challenged about this, we are the "bad guys!"

Thanks for the well thought out comments!

Russel L. O'Toole
AUDIO ELECTRONICS, Inc.

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From: Keith Kotch (Winter Springs, FL)
Subject: Re: Reverb Times

Oh John,

I'm so very sorry for you. I'm sure others pass along their condolences
too. To answer your question.......VERY!

I'm hopeful your little "test" was done in the room without carpet and
without furnishings! I think your sound quality will depend upon what
type of service you typically do....traditional, high-church or
contemporary P&W. Spoken word could be a problem too.

Keith

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From: John Hentschel (Columbia, SC)
Subject: Re: Reverb Times

The only thing missing during my clap test was lots of warm bodies.
But unless they're all 20 feet tall they won't make any difference.
Besides who wants to stand for the whole service anyway.

BTW, we use contemporary P&W. A lot of Vineyard style music.

John Hentschel
Ministry Resources

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From: Ron Hagelganz (Vancouver, WA)
Subject: Re: Reverb Times

Sometimes you've just got to drag the board or pastor or whoever out on
a field trip- take them to a church that sounds lousy and has spent a
fortune trying to but can't fix it, and then to a church that did it
right and pray they can tell a difference (which often is the biggest
problem in the first place!)

Ron

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From: Barry Birdwell (Nashville, TN)
Subject: Re: Reverb Times <"I clapped my hands, fairly hard, and it took about 3.5 seconds for the room to become quiet again.... My question is, how excessive would you consider this?">

Your organist will love it. Your pastor and anyone else who speaks will
probably hate it. The listeners won't fare too well either. It has been
my experience that reverberation times in this region, without significant
late in time reflection reduction or diffusion, will wreak havoc.
Typically about 2.5 seconds midband is about all that most speech signals
can stand. I would find out if anyone in the design team (architect,
engineers, etc.) was supposed to address this. If not I would certainly
seek qualified help.

Barry Birdwell
Birdwell Acoustics, Inc.

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From: Michael Henderson (Houston, TX)
Subject: Re: Reverb Times

From what I've read this spray will only dampen higher frequencies and
your room sounds like you probably have lots of freq. problems.

Mike Henderson
VCF Houston

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From: Bob Enlow (Norwalk, OH)
Subject: Re: Reverb Times <"Someone mentioned K-13 produced by International Cellulose a couple of months ago so I looked them up. They have a website and we are exploring the use of their product K-13 fc to be sprayed on the walls from 10ft up. This product sprayed to a 1" thickness should reduce our reverb time to 2 seconds with no other treatments.">

I have a complete set of International Cellulose literature and spec sheets.
The NRC is at its best at 500 Hz and up, but for 1" at 125 Hz, it has an NRC
of .08. If you double the thickness to 2", at 125hz the NRC is .26. The
overall NRC is .75 at 1" thickness and .95 at 2".

I hope this helps a bit.

Bob Enlow
RESOUND Co.

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Editor's Note: The conversation in this thread split off to talk about
how to get an acoustics consultant and/or sound system designer invovled
early on in a building project. For the continuation of this thread,
see the thread titled "How do I get a consultant involved during the
design phase?"

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