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



## dpak (Jan 12, 2018)

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?


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## mikefellh (Jan 12, 2018)

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.


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## Amiers (Jan 12, 2018)

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


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## MNicolai (Jan 12, 2018)

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?


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## venuetech (Jan 12, 2018)

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?


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## dpak (Jan 12, 2018)

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.


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## FMEng (Jan 12, 2018)

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.


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## MNicolai (Jan 12, 2018)

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.


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## JD (Jan 12, 2018)

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 (Jan 12, 2018)

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.


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## MNicolai (Jan 12, 2018)

Van said:


> 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.


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## themuzicman (Jan 12, 2018)

FMEng said:


> 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.


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## mikefellh (Jan 12, 2018)

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.


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## josh88 (Jan 12, 2018)

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.


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## dpak (Jan 13, 2018)

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.


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## JD (Jan 13, 2018)

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.


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## RonHebbard (Jan 13, 2018)

JD said:


> 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.


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## JD (Jan 13, 2018)

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.


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## AudJ (Jan 14, 2018)

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.


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## EdSavoie (Jan 14, 2018)

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.


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## dpak (Jan 14, 2018)

The speakers are pretty much over the stairs, so scenery wouldn't have been in the way (and the only thing close to the speakers were periaktoi that were behind them, and in front of the doors). 

Yesterday I had my student techs mic up 8 actors (Shure ULXs and headset mics, in case it matters) and the actors stood center and on the front edge. They all spoke in a fairly loud volume and only one student's mic started to feedback when pushed too high (it was a lower tone feedback - probably in the baritone range, if that helps). In general, we could get all eight at a decent level without any problems. I'm thinking (given my limited knowledge) that this is just a matter of being careful with the gain and levels of each mic, and not a deeper problem. 

I'll post another update tomorrow after talking to the sound guy.


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## lwinters630 (Jan 15, 2018)

Several things strike me, you are running a great sound board with built in compressor, all sort of eq control. To control feed back ring out your mic frequency. You may also add the HPF ( high sq 1pass filter. ) and take all high end out.
Use something like RTA to find the specific freq thats givung you trouble. 
Rigging- You touch and you are now liable. If your not qualified , please get one.

i wish you well.


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## FMEng (Jan 15, 2018)

I would be cautious about using the low pass filter. It would only be effective above about 8 kHz. Murky mics are not an improvement. A _high pass filter_ takes the low frequencies out and prevents feedback at those frequencies. Use the high pass filter set to about 100 Hz on each actor's mic. Avoid boosting EQ controls, use cuts only. 

Use compression sparingly, with a high threshold. Compressors can bring about feedback by increasing gain when the actor lowers their voice or stops speaking. 

Remember that when multiple mics are running near feedback, you have to lower the levels of them 3 dB every time the number of open mics double. For example, you have less feedback margin with 8 live mics than you do with 4.


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## kicknargel (Jan 15, 2018)

Lots of pro info here, much of which is over my head (and perhaps the OP's as well). Working from the assumption that the solution is to be found in mixing rather than installation, I might suggest that you bring in a good audio engineer / mixer for a consult, to EQ (or "ring out") the system. Then make a careful record of the settings. 

re: the Legally Blonde video. I did not know that gain riding was performed on the level of syllables. Pretty impressive. Also, they need a preset page button in a better spot (like a space bar).


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## dpak (Jan 15, 2018)

Okay, I think the main take away is that I have to make certain school admin ignores any one else's opinion on what the auditorium needs and should come to me first.

That said, the sound guy was very helpful. I explained what we did the other day and said that we don't need to move the speakers. He agreed, then went on to show my student techs some of the things they can do while mixing the show. I know just the very basics of compression, high pass filters and gating, but he was able to go into detail with the girls. 

Thank you everyone for all the advice - I owe all of you a round!


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## Ben Stiegler (Jan 15, 2018)

Um, let me pose a few more questions for you here. ( I come from a 50 year background of designing, installing, tuning and operating venue systems for theater and concert uses). 

1. Are the 2 speakers hanging together under separate amplifier control, or are they wired in parallel and fed from the same amp? Why this matters - gain for the center-fill cabinet(s) may need to be lower than the outer cabinet to manage feedback when actors are moving downstage, or there are mics in an orchestra pit, etc.

2. Without photos of the audience space, its hard to see if the aim on those cabinets is optimal. If standard spacer bars were used, vs. doing the math and trigonometry first, there may be improvements possible there.

3. What are the speaker models, please? From this we can look up the patterns.

4. How old are the speakers? Do they sound good-as-new, or do you hear distortion, grinding or buzzing from any of them?

5. While an installer's inclination is often to hang the box with the mfr logo readable (eg, the woofer on the bottom, tweeter or horn on top), often the reverse orientation is better suited to the room and the angles afforded by the hang position. Take pix from both top and bottom of house left, center, and right, as well as 1 from middle of house, looking up at the closest speaker in each case, and post them - that will help us help you.

6. Looking back in history - who designed and installed this the first time? Was it an organization that impresses you as knowing what they are doing? Would you want to invite them back for a look and a listen, or is it better to get a new set of eyes and ears in there? 

I completely agree that someone who knows how to mix ("sound guy") may be a dangerous choice if they are not also aware of rigging safety, how to calculate dynamic vs. static loads, etc. Often a structural engineer is also necessary to ensure that the place the hanging points attach to the building are strong enough to support not just the dead weight, but the momentum and side to side motion that could result from (say) an earthquake. We think about that a lot here in California 

Ben Stiegler
Performing Arts Audio
510/823-0850


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## Jim allen (Jan 17, 2018)

dpak said:


> 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.View attachment 15857


My take is that the speakers need to be father out from the stage, as someone DS CTR is standing in the cone of the speakers. Also you might be better off with a RT,CTR,LT speaker hang


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## MNicolai (Jan 17, 2018)

Jim allen said:


> My take is that the speakers need to be father out from the stage, as someone DS CTR is standing in the cone of the speakers.



You aren't in the flame of the speaker standing at downstage center. You're on the edge of the pattern off of those cabinets. Those cabinets are pointed toward the middle of the center seating section.

Bringing the cabinets farther into the room will turn a non-issue into an awkward audience experience. That's a pretty wide L/R split to begin with. Move it into the crowd and tilt down and now someone in the far right of your vision is being heard from above your head in your left ear.

In an ideal world, it would be a center cluster with coverage of the whole room, L/R fills to pick up the far left and right seating and to add a little envelopment to the acoustic signature of the system (not intended for proper stereo or LCR mixing), and front fills to bring the acoustic image down to ground level for the people seated near the front. In this case, you would probably have to cut a chunk out of that cloud and hang the cluster above the cloud shooting through fabric or metal perf.

The benefits of which would be marginal if you have someone opening a bunch of mic's on the lip of the stage, gained up for students who are still learning how to project while also trying to get enough headroom to ride the vocal mix above the pit orchestra. Only so much can be done to protect someone from improper mixing technique.


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## TDjohn (Jan 17, 2018)

Ben Stiegler said:


> Um, let me pose a few more questions for you here. ( I come from a 50 year background of designing, installing, tuning and operating venue systems for theater and concert uses).
> 
> Hello,
> 
> ...


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## JD (Jan 17, 2018)

It is important to remember that all systems will feedback. The question is, can you get acceptable headroom before this occurs? Before spending a dime on changing things, I would want to borrow an experienced soundboard op, who knows theater, to assess that there is indeed a problem, or if the solution is simply the mix/eq and expectations. Although there is some serious math behind sound, you best sound people are people who can also think in the abstract, and visualize what they are hearing.


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## dpak (Jan 24, 2018)

A quick update - things are working much better, mainly because of the tutorial from the sound guy -the girls are already much better at setting the levels and jumping on problems. The guy did find a possibly related problem - the antennas that we had on the catwalk are no longer there, and in fact had been mysteriously cut off. Grrr. We've made adjustments - moving the receivers, and the purchase of some used equipment with a working antenna system -so we should be fine for the production.

One thing that I want to do by the end of the year is to get a full inspection of the place, which probably hasn't happened since the auditorium opened about 20 years ago. But I'll save that post for after the show when I've had a moment to breathe. 

Thanks again for all of the advice!


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## sloop (Jan 31, 2018)

Make sure the sound specialist knows what he is doing. By re-aiming your existing speakers you could end up with some serious phasing issues on each side. The ones pointing in do look like they aim in a lot, but that maybe to balance phasing on the sides with the outside throw speaker. The speakers on the side of the stage are OK, but a center fill or a center cluster system overhead could help your situation a lot.


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## TimMc (Feb 1, 2018)

Uh... I think they've sussed this out, @sloop. While your observation is not to be dismissed I think it's important to remember that "phase" is a frequency-domain phenomena that exists when identical signals combine (or arrive at a common location) in a way that is not time-synchronous at a particular frequency. Normally this occurs when 2 loudspeakers (or an architectural/scenic reflection) both cover a portion of the audience area.

The center frequency of the resulting comb filter is based on the physical distance between loudspeakers/reflective surface.


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## sloop (Feb 1, 2018)

TimMc said:


> Uh... I think they've sussed this out, @sloop. While your observation is not to be dismissed I think it's important to remember that "phase" is a frequency-domain phenomena that exists when identical signals combine (or arrive at a common location) in a way that is not time-synchronous at a particular frequency. Normally this occurs when 2 loudspeakers (or an architectural/scenic reflection) both cover a portion of the audience area.
> 
> The center frequency of the resulting comb filter is based on the physical distance between loudspeakers/reflective surface.



Exactly what I was trying to convey. Changing the spread of the speakers could cause phase issues. Just because you have a "professional" advising you, doesn't mean its going to work. I have seen a lot of "professionals" screw up big time.


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## Jay Ashworth (Feb 1, 2018)

RonHebbard said:


> @JDI 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.



Why ever would you need to do that?

The 108/9 series have *noise-cancelling mics* -- both sides of the mic are open to the air, and since you're only on one side, you're (mostly) all that comes out.


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## RonHebbard (Feb 1, 2018)

Jay Ashworth said:


> Why ever would you need to do that?
> 
> The 108/9 series have *noise-cancelling mics* -- both sides of the mic are open to the air, and since you're only on one side, you're (mostly) all that comes out.


 @Jay Ashworth When you're in a room with 100 1970's vintage British Strand JTM series dimmers of a variety of sizes up to 6 Kw's and you're leaning into a telco-style, single conductor hard-patch to physically unplug and re-plug 120 VAC load circuits not only between performances but during performances while many circuits are active and many dimmers are dimming and / or fading, the coils of your dynamic mic are in close proximity to the magnetic fields being radiated from the single conductor load cables of your hard-patch. I understand what you're saying about airborne noise. The electrical cancellation of the two elements was to negate magnetic coupling and the associated unbearable hum it would induce into the unbalanced mic input of their Electro-Vox production intercom system of the day, originally custom fabricated by Electro-Vox of Montreal, Quebec, Canada. 
With apologies if I did not explain this sufficiently clearly in my post. 
Toodleoo!
Ron Hebbard.


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## Jay Ashworth (Feb 1, 2018)

Oh. The problem was EM noise, not acoustic.

Yeah, I can see that.


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## RonHebbard (Feb 2, 2018)

Jay Ashworth said:


> Oh. * The problem was EM noise, not acoustic.*
> 
> Yeah,* I can see that.*


 @Jay Ashworth To further clarify, this was back in 1977 thus some of the exact quantities of load circuits are becoming fuzzy in the crevasses of my mind. There were approximately 400 to 500 load circuits emanating from the telco-style hard patch. Smaller dimmers had 3 or 4 load receptacles per dimmer with larger dimmers having 6. I can't recall any dimmers having more than 6 load receptacles. As much as possible, cables remained plugged and loads were switched 'on & off' by switch-rated Heinneman (SP?) magnetic breakers with the aid of color-coded tape. The Stratford Festival operates as a rotating rep'. In 1977 they operated 3 venues physically scattered about the city. My first season, the bulk of my time was spent in their main building with its thrust stage. Again from memory, I believe we opened the 1977 season with 3 or 4 productions in June or late May then proceeded to add 3 or 4 more productions in August for a total of 6 or 8 productions running in their rotating rep' through to the end of their season in late September / early October with shows which opened the season being dropped from the rep' as the end of our season approached. The same pattern applied across all three venues with many of the acting company performing in all three venues with matinees in one venue followed by evening performances in others on a regular basis. In the first half of the season, booking time for maintenance was difficult as all facilities were booked solid until ALL productions were open and running in rep' when things settled down to 10 & 12 performances per week by virtue of cross-casting of Equity performers and only periodic understudy rehearsals being slotted into the schedule. I offer this to help you appreciate why physical re-patching of the telco-style load leads was often necessary during performances: There are only so many dimmer receptacles physically available on the hard-patch, even with the addition of out-board plugging boxes. [60 Amp rated 'cube-taps' if you prefer to envision them that way] Eventually you end up having to physically shuffle load circuits during rehearsals and performances thus the need for the board operator to receive confirmations of the completion of re-patches prior to executing his next cue. Nobody plans to intentionally shuffle single conductor loads while they're live and under load. Nowadays the term 'Arc Flash' leaps to mind.
Toodleoo!
Ron Hebbard.


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## Jay Ashworth (Feb 2, 2018)

By "telco-style", I assume you mean "switchboard", like a WeCo 557?

https://farm3.static.flickr.com/2713/4360697553_ba9dfacef9.jpg


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## RonHebbard (Feb 2, 2018)

Jay Ashworth said:


> By "telco-style", I assume you mean "switchboard", like a WeCo 557?
> 
> https://farm3.static.flickr.com/2713/4360697553_ba9dfacef9.jpg


 @Jay Ashworth Your assumption is correct Sir. 
Toodleoo!
Ron Hebbard.


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