Do I need to call in a professional to adjust hanging speakers?

[dpak]

Long story short, we may have to adjust the placement of our auditorium speakers due to feedback. A sound pro has talked to some one else at school, but I have not had a chance to talk to that guy yet.

Here's my concern -if we have to adjust the placement of the speakers, either by rotating the assembly on the top (from the first pic, it looks like that could be done) or by completely re-hanging them, should I be nervous about district maintenance people doing the work? Maybe this is something easy that competent facilities people can safely handle, but my instinct is that I need to get both a sound pro and a rigging company to work together to take care of this.

Any thoughts?

 

[mikefellh]

It's hard to tell from the photos...are those speakers backstage??? I assume so they are "hidden" from the audience? If that's the case relocating the speakers so they are in front of where microphones are used (so the sound from the speakers isn't directed towards the mic) and using mics with a cardioid polar pattern might be better.

In my own situation because we have a "movie theatre" auditorium (no stage with draperies to soak up sound and the screen is a solid wall), we switched to a lectern mic with a tighter polar pattern (actually, the polar pattern is adjustable with this mic) and a feedback suppressor (in setting it up you generate feedback to find and cut out frequencies that generate feedback).

But getting back to your situation, if you had a diagram to actually show the location of mic(s) and speakers in relation to each other would help us answer your question...but someone who deals with sound issues to look at the situation and tell you what you should do would be better to higher than just a rigger.

 

[Amiers]

If the sound pro directs the in house facility guys I think you will be fine.

 

[MNicolai]

I would encourage a professional is brought in to do it.

You could have district staff get scaffolding or a lift ready for them when they show up, but you can trash the output of your system pretty quickly by flipping the polarity of the boxes or adjusting the spay between them.

You also need to make certain that however they're being reaimed is still accomplishing at a minimum what they aren't currently doing, and that by moving them you are prepared to make any/all changes you need to for delay/EQ/balancing. This means having someone set up Smaart or the like and retune.

You may be solving the problem at the wrong step though. Generally speaking with a properly tuned system you should be able to walk right into the flame of the speakers with your mic open and not encounter any feedback. If you are doing musicals and have a large number of mic's out on stage, you will get hands-down the best results by throwing faders instead of leaving all of those mic's open for anyone who happens to be out on stage whether they're talking or not.

What is the nature of the way you use this system that you are encountering feedback?

 

[venuetech]

It looks to me that one speaker is pointed at the audience and one speaker is a high side fill pointed at the stage.
I assume there is another pair on the other side of the stage. Do both get the same signal? Do you have a center cluster?

 

[dpak]

Here's the auditorium (one guess as to what show we're doing). We had some feedback during our last musical, and the thought from the sound pro guy is that the inside speakers are points too far in and are going over the apron instead of completely out to the house. If we rotate each set of speakers out, the outside speakers will hit the walls. I'm a little skeptical about moving the speakers since I didn't think it was much of a problem before. I'm meeting with the guy on Monday. If it matters, we're using a Soundcraft Expression. We have a FBX 2400 Dual Feedback Eliminator that was used with our old board but is not hooked up now.

Again, I'm meeting with him on Monday and will press him on the details and possible solutions. My uneducated gut is that it is not the placement of the speakers.

 

[FMEng]

It looks to me like turning the speakers will result in a large coverage hole in the middle of the house, plus nasty reflections off the side wall. There are no magic bullets for eliminating feedback. Keeping the number of open mics low, and controlling levels carefully will resolve most problems. Re-installing the FBX 2400 would also help. There's no reason it can't be used with your console.

 

[MNicolai]

Looks like those speakers are where they need to be to cover down center, especially without front fills.

You can try using the feedback eliminator again but I find they are usually more trouble than they are worth, especially if they notch different frequencies out and are configured to hold those notches indefinitely. Then you end up with Swiss cheese EQ.

This is probably more about mixing and miking technique than anything.

 

[JD]

Keeping only active channels open as well as riding gain can be aerobic as this old video shows, but it's just what has to be done on a feedback prone situation.
(Wish they had better audio for this recording!)

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[Van]

I don't know about hiring a professional "sound guy' to move the speakers but I think you want some qualified Riggers to rehang them under direction of the Sound Consultant. Especially if they are having to move rig points.

 

[MNicolai]

I don't know about hiring a professional "sound guy' to move the speakers but I think you want some qualified Riggers to rehang them under direction of the Sound Consultant. Especially if they are having to move rig points.

Important distinctions. Most professional AV firms have installers qualified for this kind of work if in fact you need it to be performed.

"Sound guys" tend to neither be qualified in rigging nor in consulting. Unless this guy has a resume to show he knows how to design sound systems -- not just mix consoles -- don't let him near your speakers, and don't let anyone near your speakers under his direction.

 

[themuzicman]

It looks to me like turning the speakers will result in a large coverage hole in the middle of the house, plus nasty reflections off the side wall. There are no magic bullets for eliminating feedback. Keeping the number of open mics low, and controlling levels carefully will resolve most problems. Re-installing the FBX 2400 would also help. There's no reason it can't be used with your console.

I agree here -- your speakers look appropriately positioned for an L/R OUT to cover the sides and an L/R IN hitting the center section. Moving them will create a hole in the center, unless you move your outs AND add in Front Fills or a Center. That being said -- adding in FF + Center will allow you to drive the system at a lower overall SPL per box and distribute the load over the increased number of boxes.

 

[mikefellh]

Now that I see the actual layout, personally I feel that part of the problem is speaker sound bouncing off the curved ceiling panels back towards the mic(s). Then again others here probably have more experience with them than I do.

 

[josh88]

You mentioned not really having problems before your last musical (or at least not remembering any).... so what changed? Started using more mics? different type of mics? new sound guy running the system? The first red flag to me out of all of this isn't that the problem was the speakers, that it was the sound guy. Just my hot take.

 

[dpak]

Thank you for all of the advice! The thought of moving the speakers is coming from someone else at school. Before it was brought up a few days ago, I didn't think there was much of a problem, though this person claims that the feedback happens when anyone if center stage near the edge. We have rehearsal today so I'll have my sound kids play experiment to see if we can recreate the feedback - or control it with the faders and gain on the mics.

 

[JD]

A couple of other things come to mind. If there are specific locations and frequencies that are problematic, phase cancellation of those frequencies can be achieved with mic locations, EX- two microphones placed 1/2 wave apart of the axis of source will kill a specific frequency. This, however, only works with fixed mic locations and for obvious reasons will not take care of "microphones on the move." Although I am reminded of a trick used by the Grateful Dead years ago, where two out-of-phase microphones were placed on each stand, with the singer (in this case) biased toward one. All other sound entering the microphones canceled out. A similar trick can be done with Lav mics, but not head worn.

 

[RonHebbard]

A couple of other things come to mind. If there are specific locations and frequencies that are problematic, phase cancellation of those frequencies can be achieved with mic locations, EX- two microphones placed 1/2 wave apart of the axis of source will kill a specific frequency. This, however, only works with fixed mic locations and for obvious reasons will not take care of "microphones on the move." Although I am reminded of a trick used by the Grateful Dead years ago, where two out-of-phase microphones were placed on each stand, with the singer (in this case) biased toward one. All other sound entering the microphones canceled out. A similar trick can be done with Lav mics, but not head worn.

@JD The same cancellation trick can work extremely well by cancelling either electrically, polarity-wise, or mechanically with communications headset microphones such as the Beyer DT108 and DT109 when deployed in electrically and / or physically noisy environments such as telco-style hard-patches from the pre dimmer per circuit days combined with air-born intense HVAC noise.
I had a Beyer DT108 with a spare mic element glued in place on the outside [Rear] of its boom mounted microphone. It was a little heavy out on the end of the mic boom and required a little extra effort when snugging down the tilt-lock. They were wired with their polarities electrically additive but, as they were reversed / 180 degrees out of phase physically, they combined to reduce ALL electro-magnetic and HVAC noise entering the comms system while making it extremely easy to converse with the assistant LX when confirming mid-scene / mid-act physical repatches of the single-conductor hard-patches.
Toodleoo!
Ron Hebbard.

 

[JD]

The cancellation of feedback was so effective they were able to put their whole sound system behind them and still avoid feedback.

Notice, no monitors! No need as the "vocal array" is the section flown over the drum set.

 

[AudJ]

In the current photo, it appears as though the scenery can get pretty close to those speakers - is it possible scenery during the last musical interjected an acoustical plane near a speaker that dramatically caused problems? If that is possible, changing the scenery angle, or proximity to the speaker, even a little could make a difference.

In my space, the in/out position of the grand drape makes such a difference, I have two different libraries of mic settings saved to be recalled by situation.

 

[EdSavoie]

If you do wind up getting them moved, I'd be careful letting the school board's general contractors touch the speakers...

I've seen them hang cabinets in very... "Special" ways, hanging safety chains in such a way that it wouldn't stop a fall, just make that fall look visually spectacular, by ripping the cabinet through the thin plywood...

This was further evidenced by them having never seen, nor taking the time to figure out how to disconnect a SpeakON connection, so instead they chopped off the cable, which left us to find shorted wire.