Center speaker above pulpit

[balanr]

Is there any king of general distance rule for this? We have L/R speakers on the outside walls now and would like to replace them with a center speaker but only have about 10ft from the pulpit mic to the ceiling, so that would be 9ft or so to the center of the speaker. We tried a few speakers we had here, just sitting on top our 12ft stepladder and loved the sound but couldn't get any kind of volume out of the pulpit mic without feedback. I'm sure we could EQ some of that out with an equalizer of some sort, but is this just too close to work with. The speaker can only be a few feet in front of the pulpit as thats where the seating starts. The room is 40' wide and 65' deep with the pulpit 15' in from the back wall.

[Frank DeWitt]

The distance rule you are looking for is the inverse square law
http://hyperphysics.phy-astr.gsu.edu...ic/invsqs.html
As you have discovered, the closer the speaker is to the mic the greater chance of feedback. A more accurate statement of your problem is the closer the speaker is to the mic compared to the distance from the talker to the mic the greater the chance of feedback before you have enough volume.

The difference is that you can move the speaker further away. You can also move the microphone closer to the talker. If the microphone is 12 in from the talker and 9 feet from the speaker you can move th emic to 6 in from th etalker or move the speaker to 18 feet. the effect will be the same.

Some other things you can do. Make sure that the Vertical dispersion angle is a low number so less sound get's dome to the pulpit.

Perhaps move the speaker back over the 3rd row or so. (Do people sit in th efront row at your church?) Convince the pastor to use a over the ear mic. (You probably still need a pulpit mic for other things.)

Get a very directional pulpit mic.

Frank

[Brad Weber]

There are several factors potentially involved. Of course the distance from speaker to the microphone is a factor as is the distance from the speaker to the listeners.
The listeners are further away that the microphone so the loss due to distance will be greater for the listeners than for the microphone. To avoid feedback, you need the speaker and microphone to have some directionality that provides a difference that is greater that than that difference due to distance. Basically, you need a speaker that provides greater output toward the listeners and reduced levels toward the microphone and a microphone that is more sensitive toward the person talking than it is toward the speaker. So not just the physical distances but also the patterns or directionality of the speaker and microphone are factors.

Adding to that, the output and directionality of speakers and microphones varies with frequency, so what frequencies are involved can be a factor. For example, both speakers and microphones tend to be less directional at lower frequencies, so anything to reduce the low frequency output of the speaker can help.

But the basic point is that it is not just the relative locations of the speaker and microphone but also their directional characteristics and relationships.

[balanr]

We do use an over-the-ear mic for the pastor, its for the other(announcements, scripture reading,etc) things. The problem with moving the speaker to the 3rd row or so is that the rows of chairs angle towards the front at the outside, so while the people sitting in the front row center don't need the speaker anyways, the people on the outsides do.
We tried a QSC 3way model with the conical 2way coax horn which did help the feedback(I'm not sure what the crossover was, I'm guessing 500Hz) because of the directivity, but being only a 60degree horn, the sides of the sanctuary were very muffled because of the lack of highs. There don't seem to be alot of options besides Danleys, which are a bit out of our budget once you add a DSP. Renkus-Heinz has some 90X40 but the ones I saw did not have a rotatable horn and we need to keep the speaker horizontal for line of sight from the balcony issues. We have a budget of 4-5000 if that helps, that would include price for the dsp if needed. I don't know if the SM96 would do or not. Theres no place around here (southern Ontario) that has Danley as far as I know.

[Frank DeWitt]

We have s setup where if the front mains are angled high enough to catch the back row then the front 6 rows don't get any highs. We mounted a couple of small speakers connected with there own amp and a DSP channel they put out just a bit of highs and with the wash of mids and lows from the mains they sound perfect. Perhaps you could have a large center main where you want it and a couple of side fills carefully aimed and EQed so they fill the side rows but don't cause a GBF problem.

Frank

[Tim Padrick]

The published dispersion specs of most speakers won't help, as they don't tell you that at the frequencies the woofer is reproducing, most speakers are darned near (or are) omnidirectional (you need to look at polar plots to see this - and even a lot of the Danleys are like this - the only way to control lower frequencies is with a BIG horn).