church building bass traps

[gullfo]

can you send me the file to my email?

[bobmurphy]

yes thanks - do you want to pm me your mail

[bobmurphy]

here are some photos of the building - some of them are from a while back ( the balcony-like structure with the steps over what will be the stage area in the two photos titles beginning with "earlyview" has been removed in the later photos )

[gullfo]

yes thanks - do you want to pm me your mail

actually i got onto drop box but your URL is generic. can you provide a direct link to the file on there?

[bobmurphy]

sorry - i think it's http://dl.dropbox.com/u/9939843/FinalModel2.skp

[gullfo]

so... looking at it from a computational standpoint... you will likely have some issues from around 70hz-120hz and would need around 50% absorption scattered around the large half of the room and around 35% in the smaller section of the room to get the RT under 1000ms, with 60%/40% for an RT of 850ms. i would make a massive slat resonator set up on the front wall to deal with 70hz+ and hang the curtains and screens in front of that. to help, angle the slats on the vertical so they're narrow at the bottom and fill out at the top. the side walls will need some absorption as well but you'll need to find places for them.

to do this right you're probably best off with a number of 600mm x 600mm x 100mm cloth covered absorbers on the ceiling. dye the cloth to match the walls or use interior design ideas - symbols, colors, etc. treat all cloth with fire retardant.

[bobmurphy]

thanks glen, that's really helpful, and i will definitely do some of that... however i have a few problems with the slat resonator, the biggest one is that the wall ( i presume you mean the one behind the stage ) has a small problem in that i just discovered that there needs to emergency lighting in the top corners which is getting in the way of everything, and obviously it would get in the way of a slat resonator too. I also wonder how deep it would have to because it would take up precious inches from the depth of the stage ( which is a major issue for the room, as the pastors have essentially underestimated the size which would be needed for the stage, particularly the depth )
As i mentioned earlier on the post i have planned to make the stage into a bass trap and i'm wondering if this could be made to cover those frequencies ( the rough dims will be 6m by 3.5m by 0.5m ). I was also planning on putting a large number of absorption panels 705frk (which i understand to have a good bass efficiency ) on the back wall .... anyway it would be handier for me to do a combination of these two things instead and i'm wondering if i was to carefully design the stage and put as many 705frk panels on the wall would it tackle the bass issue instead of the slat resonator would you think ?

the other thing that i was thinking of was this: Would it work to try to make the stage area and the area immediately adjacent the speakers to be fairly dead while making the rest of the room ( ie the area where the congregation *sing*) to be as live as possible? This would be in an effort to keep the amplified content as controlled as possible whereas leaving the room itself nice and live for singing - i was in our current room today again and as i mentioned before it is really dead and to be honest i think it really does affect the singing so i want to leave the new room as live as i possibly can while *still* making it useful for the PA music and speech - to that extent i am still thinking of putting the polys on the ceiling like you were suggesting so im wondering if you would still think that was a good idea also ( i have found a couple of places on the net recommending an rt60 @2k of 1.5 for a contemporary church with amplified music - what do you think of this ?)

over the stage i was thinking of applying a good bit of absorption to the ceiling and either absorption or a combination of absorption and polys to the side walls

i was also thinking of putting a lot of absorption on the back wall to prevent as much slap back as i can

i would really appreciate any comments or further ideas, thanks so much

[gullfo]

i think if you put enough absorption behind the stage then it would be helpful. the polys are really good for cases where you need to preserve and scatter energy and it sounds like you have enough energy. otoh, i think 1000ms or less is probably better for your space, the 1600ms would (imho) be too much.

[bobmurphy]

thanks again glen,

Re: the rt60 level 1.0 vs 1.6 - i was thinking that it's not too difficult for me to add covered 703 panels going forward so i might deliberately aim for a higher rt60 than i actually want and then add the panels gradually over the opening weeks until the reverb level is where we like it - i know in a studio environment i could test the rt60 and tweak it so it's where i want but the congregation will play a big part in this scenario- do you know is there any way of taking them into consideration without them physically being there?

Also what do you think of the idea of making the stage area more dead and the congregation area more live - is this likely to have any effect or will it all just cancel out - the idea again being to make the pa and stage have a lower RT than the congregation singing

Question re polys: should they be filled or left loose - i read ethan winters saying they should be damped to prevent resonance

[gullfo]

the stage area can be more dead by adding more absorption overhead. that sloping ceiling though will be tough because of reflections back to the stage. the monitor placement and levels and time delays will be important to getting proper speech intelligibility and spacious music. I've seen some forum discussions where people ran two systems - one for speech and one for music to ensure best of both but this requires additional speakers, amps, and the eq and delay electronics. adding the absorption over time to get the full benefit of evaluating it with the congregation in place is a good idea. calculating the RT based on people is possible because people do have absorption coefficients...

in this case, the polys should have insulation added to dampen them.

[bobmurphy]

for the sloping ceiling would you be more inclined towards polys or absorption
for the delay i calculated that the sound differential would only be 0.02 seconds so i thought that would not be perceivable so i have ran all four main speakers from the same amp - am i mistaken ( the distance is about 7 metres i think )
do you know of anywhere on the net that describes building polys where they show a neat method of closing up the sides ( or should i just leave them open with the insulation inside in a pillow case type thing or damp them with something else )

thanks for your help

edit: meant to ask - if i test the physical room and get an rt60 of X then do you know what the correct method of adding a known figure for a given number of people to this would be - or do you know anywhere on the net that would explain a method of estimating a crowd's effect on a *measured* room rt60 .... or to ask another way how do i add an absorption co-efficient to an rt60

[gullfo]

check out the RT60 calculator on this site. lookup the human absorption coefficients and pick one from the materials list which is close enough. here's a couple of references including John's SAE site
http://www.sae.edu/reference_material/p ... 0Chart.htm
http://www.sengpielaudio.com/calculator-RT60Coeff.htm

here's an interesting paper on the topic http://www.sea-acustica.es/Sevilla02/arcgen016.pdf

on that sloped wall - i'd use absorbers first.

[FLZapped]

Better suited?

An analogy:

You have a heart problem and need a doctor.

Do you:

a) Go to a brain surgeon

b) Go to a cardiologist

They are both doctors, after all, right?

[gullfo]

do you know of anywhere on the net that describes building polys where they show a neat method of closing up the sides (or should i just leave them open with the insulation inside in a pillow case type thing or damp them with something else)

you can leave them open and use fabric covered insulation to dampen.

[Soundman2020]

Church acoustics are much different than any other room. You actually WANT a live room. People need to hear themselves in order to properly sing out during service. Therefore, you'll want the minimum amount of absorption as possible and what you do use, will be generally narrow band in nature. Diffusion is the way to go in a church sanctuary. Looking at the plans provided, I'd say there is too much absorption.

Ummmm... I beg to differ!
Contemporary churches frequently want treatment that provides suitably balanced acoustic response (as Glenn already pointed out), as for any other similar room. Too live, and the spoken word is not heard clearly and intelligibly. To dead and it is uncomfortable. Contemporary christian praise and worship music needs the same type of acoustic response from the room as any other performance space of similar characteristics, where high speech intelligibility is needed as well as good musical sound. The days of live, reverberant, "echoey" churches are numbered.

- Stuart -