# Newbie: measuring a church sanctuary



## stevewahl (May 1, 2013)

I'm a self-taught, volunteer, amateur sound guy at our church. A few of us are having discussions and perhaps disagreements on what to do to improve the sound we have. Some of the contention probably lies in the competing objectives of amplified speech, amplified contemporary music (with drums, guitars, etc), and traditional, unamplified choral music. I'll try not to bore you with details unless you want them, but it may help to know that the main problems are a section of the sanctuary that can't hear well (IMO because the speakers we have don't have a wide enough angle of dispersion to cover the area we have), and one guy wants to remove sound deadening material to get more reverb for choral singing -- which I'm worried might make the room muddy for amplified contemporary music.

I've downloaded REW. I use OS X on a macbook. I toyed with it last night on my home stereo system, using the built-in macbook audio i/o, and a Zoom H1 (hand-held recorder) as the mic, feeding its line out to the line in on the computer.

I don't currently have access to an SPL meter, or a measurement mic. I do have a MOTU 8-pre that I would probably use as the sound card when not toying around. I'm aware of the OS-X workarounds in the sticky thread.

I believe my aim at this point would be to get an objective measurement of RT60, and to compare the frequency response at a few points in the sanctuary. For example, I've seen some say that for speech, an RT60 value of 1.5 seconds is about right, but how do I come up with a single number to compare?

I'm wondering if I really need a calibrated mic and/or SPL meter to do this? RT60 would seem to me to compare the initial signal level to where it is 60db lower, a difference that I'd think would cause the mic response to "subtract out". And comparing the frequency response from one position to the other would similarly subtract out.

If I'm wrong and I need to get something, can I get by with a measurement mic, or do I need an spl meter? If I need an spl meter, has anybody ever modified a Galaxy CM-130 to give it a line out?

Thanks!


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## Wayne A. Pflughaupt (Apr 13, 2006)

Welcome to the Forum, Steve!

Wow, where to begin. First of all, there is no way for a room’s acoustics to equally accommodate the needs of traditional choral and contemporary amplified music. One requires a highly reverberant room, the other one that’s highly dampened. It’s like saying “I want to go scuba diving, but I don’t want to get wet.”

You can probably ditch the goal for meaningful RT60 readings. It’s a complicated measurement that requires an omnidirectional sound source, which is hard to come by, and any figures you've seen that weren't generated with the proper sound source are suspect. Home audio enthusiasts have “scabbed” the measurement and are spreading around the figures they’re getting with their decently-treated rooms. I highly doubt that anything they’re coming up with will translate to a public auditorium.

If the choral advocate in your church is clamoring to remove acoustical treatments, it suggests to me that your room has decent acoustics, which is good for those of us in the “contemporary amplified” camp.  That would support your contention that the “dead” places in the sanctuary are the result of speakers with inadequate coverage. So, it appears we have the classic scenario here of a church that “cheaped out” on their sound system and is now paying the price (here’s a good read on that subject). Hopefully no offense, been there myself; the “powers that be” at the church I went to for many years were so cheap on sound it drove me nuts (here are the sad details).

Along those lines, it appears you’re trying to accomplish whatever it is you hope to accomplish with REW with whatever hardware you can find laying around. I appreciate that you’re a volunteer and reluctant to pay out of your own pocket for equipment that the church should be paying for, but you can’t get adequate results from REW without the proper equipment. I hope I don’t sound like a jerk in saying this, but it’s unrealistic to expect to do this for free. We offer the software for free, and even starting from scratch (i.e. having none of the necessary hardware) you can get highly accurate full-range frequency response measurements, and virtually any kind of acoustical measurement you’d ever need, for about $200 - the price of a calibrated measurement mic and associated pre-amp/USB interface (a SLM isn't necessarily needed). By contrast I paid $500 in 1996 dollars for my AudioControl real time analyzer - what would that be, over $1000 today? - and it won’t do half of what REW will.

At the end of the day, this Forum is mainly about helping people get REW up and running. Few of us here are experts in public auditorium acoustics or church politics  which explains why your thread has lingered as long as it has without a reply. Can’t help you with the latter, but for the former you might check the Audio forum of the Church Media Community or the Church Sound area of the Pro Sound Web. 

Regards, 
Wayne


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## Wayne A. Pflughaupt (Apr 13, 2006)

Probably should add, you only need a calibrated mic if you’re interested in accurate full-range frequency response measurements. If you’re only interested in acoustics measurements, you don’t need the mic calibrated. In that case, you can find the Behringer ECM8000 or Dayton EMM-6 for around $50-60, I believe. So if you can get the MOTU up and running with your macbook you can do this dirt cheap. :T

Regards, 
Wayne


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## tonyvdb (Sep 5, 2007)

Hello Steve, welcome aboard!

I am in full agreement with Wayne so just to add to what he said I also belong to a church and have run sound for 30 years. We in the last 7 years built a new building and a good sound system and acoustics were high priority as our old building was awful and "poor sound quality" was the number one complaint next to what kind of tie the pastor was waring that sunday LOL

Sadly in todays contemporary worship service you still have many older people who hate the "noise" of a full band so proper acoustics is a must, if the guy removes that acoustic material you will be asking for far more problems than your solving. You can always have good condenser mic's to pick up choir and other ensembles but you cant remove reflections and feedback issues that it will cause if you take those measures of removing acoustic deadening material. 
AT our new church we installed 3 seperate EV line arrays with 5 in each and the sound is almost perfect from front to back (our sanctuary seats 850 people and we have two services) I would highly suggest looking at adding more speakers to get sound to those areas rather than push the volume or brightening up the EQ of what you have.


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## ceh383 (Jan 26, 2013)

PM me, I'll donate an almost new Behringer ECM8000 if you want it.
BTW, it in not calibrated...


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## aackthpt (Jan 24, 2011)

OK, I started typing a response to this, but any response that is quality and provides any reasonable level of detail is unreasonably long and probably enters territory very far afield for a self-taught, volunteer, amateur church sound guy. If you want to dedicate large chunks of your time and life to acoustics, and have a technical background, you may eventually get semi-decent answers (along the lines of someone like Chris Whealy for example).

But, my opinion is that it would be most effective, efficient, reduce headache, and probably cost less than you think to have the church hire a solid acoustics professional. To save you money they can provide you with plans that your congregation can build and install yourselves where required--but as mentioned changes to the speaker systems should also be considered as part of the fixes so you need someone knowledgeable in both areas.


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## stevewahl (May 1, 2013)

Thanks for all the responses.

No offense taken, our church did cheapen out on the sound system, especially the speakers. And they built a smaller, gymnasium shaped room to be the "temporary sanctuary" but the expansion plans will probably never happen from what I can see. The room is essentially a single basketball court without the baskets but with the high ceilings, and the altar/pulpit/etc is centered along the long side, musician's area in the front right corner. If we'd come at it the long way the speakers wouldn't have needed such a wide spread.

And I am trying to be frugal myself, but I do understand that sometimes money needs to be spent. If I get a measurement mic, but don't have an SPL meter, is that useful? (Wayne, I don't think you sound like a jerk in any way. I can handle the truth.  )

How does one find a solid acoustics professional? Minneapolis, MN area. I'm guessing that I'll get "why
do we need to hire somebody when we have this other guy?" though, so that's why I'm looking for some objective data that I can bring to the discussion. Wish me luck!


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## aackthpt (Jan 24, 2011)

stevewahl said:


> And I am trying to be frugal myself, but I do understand that sometimes money needs to be spent. If I get a measurement mic, but don't have an SPL meter, is that useful?
> 
> How does one find a solid acoustics professional? Minneapolis, MN area. I'm guessing that I'll get "why
> do we need to hire somebody when we have this other guy?" though, so that's why I'm looking for some objective data that I can bring to the discussion. Wish me luck!


A measurement mic without an SPL meter would be useful because essentially all of the important measurements are relative not absolute. Just set things so when you listen at the mic, the test tones sound well above the noise in the room by ear. You could look at charts of how loud some normal sounds are to guess at the SPL you run your test at (likely to be 75-85 dB SPL) and rough-calibrate REW's levels so if you post graphs people don't say "wow that's crazy". Anyway, if you want to do it max-cheap then take the offered ECM8000. It will probably be accurate enough for your purposes, and hey, free or just shipping is a great price to start getting used to REW. Only problem is you will still need some other gear...

As far as how to find an acoustics guy? Well actually I'm not 100% sure (LOL I realized that was a problem after I wrote the email), but the first thing is don't go to anyone whose main business is selling speakers/audio systems OR acoustical devices. In your situation I don't know if they might have to visit, but for ground-up acoustical design they often work remotely by pictures and drawings, and possibly acoustical test files, emailed back and forth. Anyway I'll shoot you contact information for someone that I think would be honest enough to tell you if he thinks you need someone more local who can visit (and will probably know how to find someone that can do what you need).

All this talk has got me wanting to build a dodec again, LOL.

I found this document that seems to discuss tradeoffs not requiring adjustable acoustics (it says they are generally undesirable, I don't know about an average church but certainly in a cathedral as it were. Also, when I mention congregations building devices, I'm mostly thinking about this page.


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## stevewahl (May 1, 2013)

Chuck,

I can't PM because I'm not at 5 messages yet, so I'll say this publicly.

I'd feel guilty taking your ECM8000 because I can afford to get my own, which is what I will do. If only because I'm sure there's someone else out there who could use it and can't afford it as well as I can. But, truly, thanks for the offer.

And John, thanks for the SPL meter vs. measurement mic info (and other stuff, too.) I have some reading to do!


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## ceh383 (Jan 26, 2013)

stevewahl said:


> I'd feel guilty taking your ECM8000 because I can afford to get my own, which is what I will do. If only because I'm sure there's someone else out there who could use it and can't afford it as well as I can. But, truly, thanks for the offer.


No worries, it's just sitting in my office not being used. I figured a donation for a church is better than collecting dust...


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## aackthpt (Jan 24, 2011)

stevewahl said:


> I can't PM because I'm not at 5 messages yet, so I'll say this publicly.


It turns out I can't PM you either, and I really don't think I should post this sort of thing publicly so as to avoid stepping on sponsors' toes. So, how about you make a couple posts in the Post Padding Thread and then I can shoot you the info.


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