Easy to set up and take first measurements

[Dan Thompson]

For me, REW was a cinch to setup and take some initial measurements. And then I realized I don't have a clue where to measure, how really to analyse the results at any deep level, and finally what corrective actions to take.

I'm working on our church's sanctuary. It was set up 15 years ago with a pair speakers at front of the front of the room above the proscenium, and then speakers, wired in pairs, 8 feet up on either wall, pointing straight out, perpendicular to the wall, spaced 12 feet apart. Everything set up for mono. Upgraded to a Behringer X32 mixer, which seems to work perfectly well with REW. The room is 56 feet long, 36 feet wide. No sound treatments other the ceiling is acoustic tile. I set up delay lines on the side fills, and we think it helped cut some muddiness and improve clarity. But now we want to make better, more educated guesses at what to do.

My gut tells me I should measure with the two mains mains on and the side speakers turned off, taking maybe 9 measures in a 3x3 grid in the room, at sitting height. WIth or without the padded folding chairs set up in the room is one question. Turn the ventilation system off or leave it on? That's another question. That would prove to me that my db drop calculations log20(x/y) were correct or not. I expect a 12 db drop from first row of seats to last row, which is one thing I want to fix. These measurements might also tell me where lows might be building up, where the highs are going. It should also tell me what I have to boost or cut to get the room more or less level across the spectrum, or at least down the middle of the room. We know there's an echo off the back wall from my initial measurement (The IR graph showed a repeat at 60ms, the mic was 32 feet from the back wall, so that seems about right. I think that's what it was showing.) And then based on the dropoffs I can start to bring up the side speakers to fill in properly and EQ them for the missing frequencies in their area of custody. I don't know of REW will help with this, but it seems like it will.

Does this sound like a good workflow? I think it will help me with setting levels and EQing, but I have no ideas about treatments.

 

[John Mulcahy]

Turning off the ventilation should help lower the background noise. If the chairs are usually in place when using the space best leaving them. If you have more than one speaker playing the measurements will have a pair of peaks in the impulse response unless the mic is exactly the same distance from each speaker, complicating the interpretation of the results. Generally better measuring speakers individually. Note that if the room is symmetric and the speakers are symmetrically placed across the width there will be differences in the modal response when both are playing as the odd order width modes will not be excited. If you use a timing reference when you are measuring you can measure individual speakers then see the combined response by adding the results in the trace arithmetic option of the All SPL graph.

 

[Dan Thompson]

I probably didn't do everything exactly right, but I followed this advice the best I could. And I read through the manual a few more times. As a result REW gave us great insight into our church's sanctuary sound. We had been guessing that we would have to spend money on room treatments until we saw our RT60 was right around where it should be. We learned that all of our side speakers had an enormous peak at 150hz, and that the front speakers were actually pretty good but could be aimed better. We generated EQs and plugged them into our X32 mixer, and everyone agrees there is a night and day improvement in the room sound. So I made a small donation to REW because of the impact it has made in our church.

 

[John Mulcahy]

That's great to hear Dan, and thank you for the donation!