PA System Problems...

[DDroke]

Got hired on as an engineer at a church. After being very unhappy with mixes for several weeks, I started thinking I'd tune the room myself. My reference music sounds a lot closer now, which is good, but there's still some weirdness going on. Walking around the room, I can hear a lot of phasing happening in all frequency bands of low, mid, and high. I've also discovered after sweeping some pink through the room there is no crossover in the system. On top of that, the three line array stacks we have do not have any DSP calibrating them. The system is set up to run Mono and the install is done up so tight I don't have access to the audio after it leaves the board from the mono out. Line array is JBL with crown amps for each box, and I think they are either dual 8" or dual 10" boxes - too high and no lift for me to know and I haven't gotten that far in the user manuals yet. Subs are dual 15" boxes, not sure if they are powered or not. My amp rack has amps that are labeled for a few 70v systems which are fed by a matrix for a hallway mix, a few other amps for my front fills which are coming from my mono mix (also receiving full range), and lastly the rest of the amps for floor wedges. We also have Momentum to handle routing and splitting (recording console in another room). The only paperwork the install company left behind was User/Owner Manuals for each piece of equipment installed, no diagrams.

Aside from calling the company that did the install, is there anything I might be able to do to help with these problems a bit quicker? I know there are a lot of unanswered variables for everyone here, but any help is appreciated.

[rwhealey]

I'm having a bit of trouble visualizing the system - are there three line arrays hung left, center, and right, but all three are fed the same signal? Most line arrays have very wide horizontal coverage, often making them poor tools to use indoors. Can you show us a picture or draw a diagram?

What mixer are you using? Also, what model of Crown amps? The Itech series has built in DSP.

I'd find out what the install company has to say - try to have one of the system's designers run you through what you've got.

[DDroke]

Yes there are 3 arrays with 7 boxes each aimed center left and right. They are spaced a fair bit apart. The stage is center, and the seats spread in a half circle from the stage. I will post pictures later this week, most likely Saturday.

Running an M7CL console. There is one signal leaving the board feeding the system, coming off of my MONO channel, which is routed out of the console through one of my OMNI outputs.

I'll have to get some binoculars to check out the amps on the back of the arrays. Pictures soon to come though. I'll include the amp racks in my room, the momentum racks, the room itself, and possibly the amps on the array if I can get zoomed in well enough.

Thanks

[hbphotoav]

I'd say first call is to the install company. If they blow you off, have the business administrator at the church make the followup. Part of their responsibility is to provide access at least to information regarding the system design and wiring... unless they have a contract for exclusive maintenance/repairs. But that, too, is a question for the business administrator.

Be good to know as well if your poking about will nullify, void or transgress the contract/warranty between the church and the installer. Wouldn't want to mess with that, if one exists. More info is always better than less.

[edva]

Phase shift? Did you use the EQ in the M7 to tune the room?

[DDroke]

Originally Posted by edva

Phase shift? Did you use the EQ in the M7 to tune the room?

Yes I used the onboard EQ (insert -> rack geq31band -> mono) for the room. There is no outboard processing.

The phasing I am hearing is when I move to different locations of the room. At the top and bottom of each array's throw the highs become a lot more apparent. In between the top and bottom, the highs disappear and the mid range really sticks out.

[hbphotoav]

Originally Posted by DDroke

Yes I used the onboard EQ (insert -> rack geq31band -> mono) for the room. There is no outboard processing.

The phasing I am hearing is when I move to different locations of the room. At the top and bottom of each array's throw the highs become a lot more apparent. In between the top and bottom, the highs disappear and the mid range really sticks out.

Sounds a lot like the setup on the arrays is not quite right. Either there are phase problems in the wiring between the boxes (or the amplifier channels driving them), or the level balance through the curve is way wrong. Without analysis and access to the main array processing, there's not much you can do. Further EQ may just exacerbate the problem.

So, I'll reiterate... call the installation company. Or, bring in someone knowledgeable enough to get inside the lockdown and adjust the system.

[mixedupsteve]

Originally Posted by hbphotoav

Sounds a lot like the setup on the arrays is not quite right. Either there are phase problems in the wiring between the boxes (or the amplifier channels driving them), or the level balance through the curve is way wrong. Without analysis and access to the main array processing, there's not much you can do. Further EQ may just exacerbate the problem.

So, I'll reiterate... call the installation company. Or, bring in someone knowledgeable enough to get inside the lockdown and adjust the system.

I agree. You might be able to improve it a little bit but line arrays need DSP and nobody runs them without it.

[Roland]

Originally Posted by DDroke

Got hired on as an engineer at a church. After being very unhappy with mixes for several weeks, I started thinking I'd tune the room myself. My reference music sounds a lot closer now, which is good, but there's still some weirdness going on. Walking around the room, I can hear a lot of phasing happening in all frequency bands of low, mid, and high. I've also discovered after sweeping some pink through the room there is no crossover in the system. On top of that, the three line array stacks we have do not have any DSP calibrating them. The system is set up to run Mono and the install is done up so tight I don't have access to the audio after it leaves the board from the mono out. Line array is JBL with crown amps for each box, and I think they are either dual 8" or dual 10" boxes - too high and no lift for me to know and I haven't gotten that far in the user manuals yet. Subs are dual 15" boxes, not sure if they are powered or not. My amp rack has amps that are labeled for a few 70v systems which are fed by a matrix for a hallway mix, a few other amps for my front fills which are coming from my mono mix (also receiving full range), and lastly the rest of the amps for floor wedges. We also have Momentum to handle routing and splitting (recording console in another room). The only paperwork the install company left behind was User/Owner Manuals for each piece of equipment installed, no diagrams.

Aside from calling the company that did the install, is there anything I might be able to do to help with these problems a bit quicker? I know there are a lot of unanswered variables for everyone here, but any help is appreciated.

Just a quick reply, but, with all the stuff you say the system has, it must have DSP control, you can't be running that without. I suspect that they may be using DSP in the Crown amps. Why the system is running in mono sounds a little strange, however, it may be that was specified originally to make sure amateur hands on the desk didn't do anything silly that meant only half the room would be hearing the "message".

A quick call to the install company should (if they are any good) tell you what is what with the system. On an install, they system should have been calibrated to the room, meaning that little or no interference with set-up should be needed.

There are companies out there that do not do good install work, and systems performance can significantly vary if they have been ill treated, or adjusted by those with little or no knowledge of what they are actually doing. The very fact that little user access has been offered, should suggest that care was taken to put the gear in, however.......................

[fifthcircle]

If you're running an M7, you can also set different delays on the omni outs (as a matter of fact, that is one of the only delays in the whole board). So one output can in fact split out with different levels and different delay times through the omnis.

Depending on the room setup, I could see a rig like this working just fine- especially if the stage juts out into what is a more circular or arked seating area. You have a center and flanking sides that cover the whole seating area. As the speakers throws don't cross, a mono system is required.

Also, while you may not see outboard DSP, some of the amps may have the dsp built in. I'm seeing that more and more on the PA systems I rent. Your 70v amps are definitely not PA- that is all long run, mulitple speaker indoor systems. Hallways, cry-rooms, offices, etc...

Can you quantify why you are hearing phasing? Is it slop that is bouncing from somewhere? Is it between speakers? Is there some sort of polarity issue going on with the wiring of the system?

--Ben

[Thomas W. Bethe]

One of my interns was the mixing engineer for his church. They had a very nice looking system with all top quality gear but he could never get enough level out of the system. He asked me to trouble shoot the system. I brought down all my acoustical test gear and we started "proofing" out the system. The first thing we did was to check the phase on the two speaker line arrays which were hung together over the stage. They were wired out of phase so the harder the system was pushed the less sound came out into the auditorium. We corrected that and then they had plenty of level in the church. The next problem was that it really sounded all boom and hiss with no midrange. I went to the equipment room and saw that someone had changed the equalizers setting so they boosted the lows and the highs and cut the mids almost completely. The equalizers had a security cover on it secured with security screws and I was unsure how we were going to flatten out the response curves when my intern showed me how you could get a pencil in under the security cover and move the knobs with the eraser. So much for security. We spent a day getting everything setup and checked out and I was invited to come back the next day, Sunday, to hear the results. It was a vast improvement and after the services a lot of people came up to my intern to ask what new equipment they had installed because for the first time in years they actually heard what the pastor was saying (yes it was that bad).

As to what the OP can do. All good suggestions from others and I would only add that there maybe some acoustical problems in the church that were not fixed when the new system was put it due to costs or ignorance and no amount of DSP (IMHO) will correct for bad acoustics.

Best of luck!

[Rolo 46]

PA such a variable art, so easily abused.