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Amplify building wiring

Discussion in 'Sound, Music, and Intercom' started by Sayen, Jan 27, 2009.

  1. Sayen

    Sayen Active Member

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    Strange question - I'm setting up a rig in a new facility, and signal strength from the stage through the house snake to the booth is extremely weak. Wireless mics are giving me a stronger signal than wired mics, and I'm wondering if the runs are too long, or if something else strange is going on. I've heard a few industry types mention amplifiers for the lines - can anyone chime in with some experience with these? Is there a specific cable length where they should be used? Brand names to look for?
     
  2. avkid

    avkid Not a New User Fight Leukemia

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    How big is the room?
     
  3. museav

    museav CBMod CB Mods Departed Member

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    Can you tell use more about the situation like how things are wired, what distances are involved, if the signals are so low to where you can't get enough gain on the mixer and so on? And on the wireless, where are they located and are they run as mic or line level? Many wireless receivers provide both mic level and line level outputs so while you could have some real problem(s) it could also be as simple as the wireless mics being line level signals while the mics are mic level.
     
  4. Sayen

    Sayen Active Member

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    It's more of a general troubleshooting question. Audio is not my expertise, and while I can operate and manage equipment, I don't know or understand every toy out there. Several 'experts' have told me we need transformers/amplifiers in the line considering the distance of our runs, and I don't know enough myself and figured I'd bring it to the real experts here.

    The theater seats around 1000 people, and the wiring runs up through the house, multiple junctions, splits into multiple sends. The audio company who did the installation will not turn over schematics or discuss the issue, and I'm too low on the pecking order to demand that information. The wiring could easily exceed 300 feet or so through the house.

    I'd have to check the wireless receivers - fairly certain everything is mic level.
     
  5. museav

    museav CBMod CB Mods Departed Member

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    Well, if you can't get the contractor to turn over drawings, which is not a good sign, then for your own and everyone following's sake I recommend that you try to create your own documentation. It unfortunately sounds like the system may have been poorly designed, or at least designed to meet a budget rather than for functionality, and thus fixing it may take considering how everything works.

    For example, you could introduce some remote preamps but where do you put them and how do you control them? And if you did add them, would it be better to use preamps with multiple outputs to address some of the splits you mentioned?

    How old is the system? You mentioned it being new and while it may be the fault of the administrators and system designer, as in what was designed and specified, as much as the Contractor, if the system is new you really should have receive documentation and training. So there may be a question of whether the system has actually yet been accepted or is under a system warranty. In either case, the installing Contractor should be responsible for either fixing it or providing a reasonable explanation.
     
  6. Sayen

    Sayen Active Member

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    Poorly designed doesn't begin to cut it, but I'm hesitant to post details publicly, even semi-anonymously. The last professional to come through started laughing when I walked him through the system. Suffice to say, several years of prolonged meetings, testings, and bringing in multiple experts has failed to solve the issue. At this point, I'm close to buying my own snake, running it through the house, and purchasing my own gear to go with it.

    I think some companies see 'Public School' in the install line and get $$$ in the eyes.
     
  7. museav

    museav CBMod CB Mods Departed Member

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    Actually, many good companies see "public school" and run! A very common scenario is that the audio and lighting get lumped in under the electrical. So the Electrical Engineer, who may not have planned on designing those systems and may even find themselves essentially forced into dealing with these systems, gets a dealer or rep to 'design' the specialty systems for free, getting exactly the value put into it (nothing). That then gets awarded to the bidder with the lowest price, often the same party that put the design together and specified the system such that only they have a real shot at it, who then do nothing more than they absolutely have to.

    Or it can be like one public school I had where the the school thought it was a good idea to have everything from security to audio under one 'low voltage' Contractor, so they awarded the project to a firm who may have been well qualified for security and CCTV but whose audio experience went about as far as school classroom PA systems. They then tried to substitute PA and intercom equipment for just about every item in the theatre sound system. When they realized they weren't going to get away with that type of thing, in order to hold on to the rest of the contract they ended up subcontracting someone who had some idea of what they were doing, even though they did so at a loss. The sad thing was that since they did not have a TD hired when this happened, if there hadn't been a Consultant involved then nobody probably would have any idea of the difference and the school probably would have ended up with a nice, big new theater with a Bogen PA system in it.

    On another project, we designed a nice little system for a theatre renovation in a public school and although what we did was nothing fancy at all, I ended up having to defend our design to a school board that wanted to put in the same single, omni speaker system with a mixer/amp that they had used in the gym. The school even sent us the equipment list from the gym PA system and told us to design around that, at which point we told them we could not do that since we would be liable and what they were asking would not work. We said that they could bid what we designed with us involved or do whatever they wanted but without us being part of it. But the dealer that sold the gym system was happy to sell them the same thing for a theatre.

    They're certainly not all this bad, I've seen public schools where things worked out quite well, but I will say that the worst design and bid documents I've seen have been for public school theatre and auditorium audio systems.
     
  8. FMEng

    FMEng Well-Known Member Fight Leukemia

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    In general, you can't compare the level from a wired mic to a wireless mic. Nor can you compare the signal level of one wired mic to another wired model. They all have different output levels, and will require different preamp gain settings at the mixer. For example, an SM58 will need a whole bunch more gain than an ND-757.

    The question is, can you get enough electrical gain in the mixer preamp to get proper levels in the house, and can you do so without excessive noise? If so, you have nothing wrong.

    Long mic lines are not likely the problem. Any appropriate cable does not attenuate the signal from the microphone appreciably. Three hundred feet should be no big deal at all. If the system has some kind of mic splitting system, to feed two or more consoles, that is where I would look for the problem. If you don't need splits, it shouldn't be too costly or difficult for a qualified individual to remove the splitters from the system. Splitters are not inherently bad, but yours could be badly designed or improperly installed.

    I always prefer transformer type splitters, with one direct connection and one or more secondary outputs. Resistor pad and active (amplified) splitters tend to be more problematic.
     
  9. Sayen

    Sayen Active Member

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    Transformer - I think that was the word I was looking for. There are at least three major junctions/splits in the line, that I know of. We have excessive noise with a mic. Heck, we even have excessive noise with no inputs and the mains all the way down.

    I'm not expecting the signals to be the same, I'm just looking at symptoms of a botched install and trying to explain to contractors and supervisors why the problems exist.
     
  10. mnfreelancer

    mnfreelancer Active Member

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    This could be the key phrase to unlocking your problem. Would you have excessive noise if you, say, unplugged the console from the downstream equipment (amps and/or powered speakers)?
     
  11. Sayen

    Sayen Active Member

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    Haven't tried that yet. Um, of course I understand exactly why I would do that, but for forum lurkers, can you explain what that would accomplish?
     
  12. museav

    museav CBMod CB Mods Departed Member

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    If all these problems existed from day one, including the lack of documentation, then you seem to pretty clearly have a bad install. However, "bad" and not per contract are two very different things. It is the 'not installed per the contract' issues that could give you some legal grounds regarding the original design and installation.

    These steps may not be practical, but they could be immensely helpful. Somewhere there should be Bid Documents consisting of drawings and specifications that define what the installing contractor was to bid to provide. There may also be some subsequent documents such as Change Orders that together with the Bid Documents define the Contract Documents. The Contract Documents define the equipment, services, documents, performance, etc. that the installing contractor is contractually obligated to meet or provide.

    If the Bid Documents were good they would define not only the system concept but the specifications would also define the documentation, warranty and so on there are to be provided as well as identifying specific testing and training requirements and some system performance requirements. If you have such documents and can find them, then that could be a great help in identifying if the installation indeed complies with the requirements they identify.

    What you may find is that the bid documents do not properly define such requirements and either use nebulous terminology like "workmanlike" or "acceptable" or simply do not have any requirements defined beyond installing a list of equipment and having sound come out. This is poor design practice, but if this is the case it basically leaves you in a very tenuous position in claiming anything was not done properly. You essentially have to be able to point to some condition or requirement of the Contract that was not completed or violated, the technical term is non-compliant, in order to have grounds for anything actually being considered 'wrong'. It basically comes down to that of it isn't a code or life safety issue and isn't either required by or a violation of the Contract requirements, then it doesn't really matter.

    Unfortunately, many public school audio and theatrical systems bids fall into the latter situation, making it very difficult to specifically identify anything being 'wrong'. But you may get lucky and find something in the specifications or drawings that does relate to some of your problems and that gives you a much stronger basis for claiming that it is indeed an unacceptable installation.
     

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