Infinite Baffle PA sub

[SQCherokee]

Anybody know of an application like this? I may be incharge of helping the church my friend works at with updating their sound system. The sanctuary is about 80ft wide by 150ft long by 15ft high. Meaning the empty room is about 180,000 cubic ft. (yes I think in cubic ft not liters)

They are trying to get into the swing of more contemporary services, meaning live band instead of cd tracks. So they want to upgrade the sound system.

I know from previous experience that you an build a pro sub for waaaay less and have built a couple of folded port subs that were tuned to about 30hz using peavey drivers. Good SQ.

However they don't want to give up any room on the floor to speakers.

The wall off to the side of the stage has a really large storage room that is completly empty and is isolated from the rest of the room and would make a perfect IB chamber.
Would this be ideal for this type of application?

[Mike P.]

Interesting concept. Live bands would mean extension down to 30 hz. For modeling purposes how big is the "really large storage room"? Is there a budget for drivers and the required amps?

[SQCherokee]

storage room is about 15ft wide, 15ft tall, 30ft long, so it would be infinite. door is only on other side of room and they don't share hvac

no budget set yet, however I think that 4 fiQ's and 2 berringer 1000's would put them below the price that the local sound shop would charge for a single jbl 18 and a 1,000 watt amp

[Mike P.]

Here is what 4 Fi IB3 18's would do in the given volume with 2400 watts input power and a Hi-Pass filter at 14 hz. I'm not sure that would be enough SPL for that size of room.

[looneybomber]

I've gone to one of son's play/sing-a-long thing's in a church in a room bigger than that. They had two Yamaha bass bins with what looked like a single 18 in each. It was plenty for that kind of environment and music.

...If it was in a club or theater, I would have laughed and walked out.

Remember, 127db@1m is a tad over 100db at 20m (about the middle of the church), which louder than my mom and grandma would like. If it was me, I'd go with more subs, but 4 could be a good starting point.

My next thought was the people in the front row are going to get BLASTED while the people in the rear will have output in the 90's db area. Multiple subs and speakers are needed. Either that or just good speakers running down the side walls and keep the subs up front? (time delay issues, but ah well)

[Mike P.]

I agree on multiple subs and speakers placed in the room but apparently that isn't an option.

[SQCherokee]

I used to volunteer for the audio team at my church, every christmas they do alot of traditional organ music. The installed subs only play down to 35hz, so during this time they bring in a couple extra subs that extend down to 15hz.

The opening organ part for "A mighty fortress" has some really really low notes. Because of the holiday they only had me come in for the service and let me stay home that morning with my wife instead of come in at 6 for the practice. So all morning I was mixing on the fly I hadn't heard that song yet but it was hilarious because when she played those really low notes I think I shook some dentures loose. First service is usaly the retirement crowd.

It was a fun day.