Installs IT guy tasked with replacing middle school auditorium sound system (long post)

[wolfman95]

As the post title indicates, sound is not my area of expertise, but in the world of American public school district IT, if it runs on electricity, the IT guy is considered the qualified individual to work on it. We have an auditorium, built circa 1960/refreshed circa 1980, whose sound system is deceased. No local theater service company will work on it anymore...they have all indicated it is time for a refresh (amps are shot, speakers are shot, and even the cabling is shorted behind walls, presumably from (hopefully past) rodent activity. Administration can't entertain the quotes for refresh (because money is so tight), so they initially told me to get something working. I put together a portable amp/speaker system, which allowed continued use of the space this past school year, but they now want something more permanent to support the school's drama and music programs, as well as school assemblies and board meetings. I've met with the school's drama and music departments to go over what is necessary and what is not for them. I've tried to pare things down to the bare minimum that still has the functions they want. After a lot of reading, I've tried to create a setup that is relatively simple, easily serviced, and well-supported, but where I just don't have enough expertise is in cabling tolerances/distances and antenna placement. I was hoping someone with expertise could validate/invalidate my design.

I have provided 15 wireless microphones, monitor speakers, front of house speakers, a subwoofer, amps, a sound mixer with a USB interface for a computer/recording, and an antenna distribution system. All of the equipment, save for the speakers and antennas, lives in the elevated sound booth at the back of the 100' deep by 150' wide auditorium. In the booth, everything except for the mixer, is mounted in an equipment cabinet. The cabinet contains:

• A rackmount power distribution unit (fancy power strip), CyberPower CPS-1215RMS
• 15 Wireless receivers, a mix of Shure QLXD24/SM58-G50 and Shure QLXD14/83-G50
• 5 Antenna Distribution Units, Shure UA844+SWB (4 of them will connect to 3-4 receivers each, and then uplink to the fifth, which will in turn connect to the actual antennas)
• 1 Crown DCi 2|1250 amplifier to drive the subwoofer
• 1 Crown DCi 8|300 amplifier to drive four front of house speaker arrays and four stage monitors

The mixer is a Soundcraft Signature 22 MTK Mixer and Audio Interface with Effects, with the first 15 channels dedicated to the microphone receivers. The audio out from an existing Kramer video switcher/scaler that hosts a computer, a Chromecast, and a Bluray player will occupy another channel, which will leave six additional channels for future expansion.

As the microphones will be used on the stage 100' away from the booth, I selected (2) Shure UA860SWB antennas to connect to the "master" UA844 antenna distribution unit via (2) 98' Shure UA8100 pre-terminated BNC-BNC antenna cables. I did this to allow placement of the antennas above the front of the stage to avoid any reception issues. With the antennas being omnidirectional, speakers that wished to wander into the seating area should still have coverage.
The four front of house speaker arrays are QSC AD-S162T-BK units with (2) to be placed on the walls on each side of the stage and another (2) to be placed halfway to the back of the auditorium on the walls.
The subwoofer is a QSC E118SW unit to be placed on the floor beneath the front right speaker array.
The four monitors are QSC AP-4122m units to be hung across the stage behind the upper valance curtain, facing the stage (not sure if that is right term for the curtain, but that's what my wife calls it at our house).

My concerns:

1. Is the antenna distribution system designed properly? I've read a lot on them, but this is definitely not my forte.
2. Are the selected antennas appropriate to the distribution system, microphones, and space?
3. Are the antenna cables going to be OK at that length? Do I need better cables (like LMR-400)? Or would I be OK placing the antennas closer to the booth?
4. How far apart should the antennas be from each other?
5. What type/gauge of cabling should I be using from the amplifiers to the speakers/subwoofer to ensure good signal? Because the booth is elevated and the cables will have to traverse the ceiling and then the height of the wall, the length will exceed 100'.
6. Do the amplifiers I have chosen appear to be a good match for the speakers?

Of course, if you have any additional concerns that I have overlooked in my ignorance on this subject, I humbly seek your guidance. I am appreciative for the guidance this forum and its members have provided in helping me to learn enough about audio to concoct this design, and I also extend my appreciation in advance to any who respond to my post.

 

[microstar]

You do not have any type of system processor/EQ specified. How did you arrive at the correct main speakers to purchase and know they will achieve proper coverage of the seating area?
There should be money made available to hire a trained professional to determine the location of the main speakers (see above) and install them, correctly program the wireless frequencies, and TUNE THE SYSTEM!
The amplifiers might be better in a rack off stage to be closer to the speakers, but then you would need some sort of remote power sequencer.

 

[themuzicman]

Is the antenna distribution system designed properly? I've read a lot on them, but this is definitely not my forte.

It's fine for the purpose, and everything you have planned is intelligent and well thought out. It's more cascading than I'd normally like to use personally, but Shure only seems to want to offer 4 Outs + Cascade. 2x RF Venue Distro9HDR's would set you up well, but it'd add more to the pricetag for an incremental performance bump and you wouldn't need the second diversity zone on them.

Are the selected antennas appropriate to the distribution system, microphones, and space?

It's not ever really my preference to use Omni antennas for receive however you know your needs best, and if you are really concerned about audience coverage then maybe that's the move. I'd probably use LPDA's like the Shure PA805SWB or the Sennheiser A 2003-UHF and my guess is that you'll get decent audience coverage just from multipath bounce in the room, plus an LPDA will let you focus the bulk of the receive side on the stage proper.

Are the antenna cables going to be OK at that length? Do I need better cables (like LMR-400)? Or would I be OK placing the antennas closer to the booth?

The cables you picked out are rather lossy - for the same price as Shure's list price on their cable you can pick up some PWS Ecoflex or 9046 and know you have something that isn't as lossy for the long run. If you can't have the receivers side-stage with antennas just a bit above head-height, then running longer low-loss cables is definitely the right move.

How far apart should the antennas be from each other?

A few feet at minimum, nothing huge. However I'm thinking about what happens when someone turns upstage versus downstage and the reality of set-pieces being constructed upstage with folks behind them if your theater program ever makes large walls of flats, or makes a house onstage or something of that nature.

Because you're planning on going overhead I'd do an upstage antenna and a downstage antenna. Because you're the IT guy and probably don't have time to experiment, I bet an FOH Antenna (or a box-boom or catwalk if your facility has those) and an Overhead antenna combined with LPDA's would give you the audience coverage you want without sacrificing the stage. The deal here is that you'd need to gain-match the cables if you're running say a 25' and 100' - the Ecoflex I linked you'd be fine to run a 25' and a 100', you're getting like -1.25 dB of line loss @ 100' but you really don't want more than like 3dB of difference in line-loss before you have to start using attenuators to match the shorter run to the longer run's loss otherwise you can incur false diversity which is why I avoid the Shure cabling.

------
Another thing to think about - will 15 units in G50 really service your location the best? If you DM me your zip code I can do a quick coordination and see what's up, or you can use the system tool in Wireless Workbench.

 

[Ben Stiegler]

Qlx is probably overkill

Consider an RF venue unified diversity antenna

Where the heck are you? I think you are over speccing - and delay speakers add complexity of tuning and placement

One of us grizzlies may be close enough to help

 

[Jay Ashworth]

No further?