Outdoor sound system (not for movies)

[Marcel Birgelen]

In the past I used a couple of "Y" connectors to connect both the sound system and the radio unit to the the RCA line outs, but had decided to try the 1/4" cable this year...maybe that was the problem. I didn't have my Y-adaptors with me that day so I couldn't fall back to the old way. The Cobra documentation says you can use both outputs at the same time.

Neither of those connections is balanced. You say the transmitter is not connected to your rack? Is it connected to a different power socket? If so, then there's most likely your problem, as that's how ground loops are created.

If you can't connect the transmitter to the same power socket and have no possibility to introduce a balanced connection between the player and the transmitter, then a ground loop isolator is the safest bet. Removing the ground from a device, while probably solving the issue, is not a safe option. We have a bunch of ART DTI ground isolators in stock, which we deploy once we need to hook something unbalanced and external up to an audio system. They usually work fine, without really noticeably impacting sound quality. They do attenuate the signal slightly though. Those ART DTI boxes might be in the $100 ballpark figure, but you'll be able to find cheap isolation transformers for $10 to $20 on Amazon.

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[Tony Bandiera Jr]

Tony, the transmitter is not ours, it belongs to the fairgrounds. It's a cheapo Chinese thing. (It's worked fine in the past though.) It's not connected to the rack, it's just plugged into one of the line outputs on our music player, which is a Cobra Firing Systems AudioBox. I'll see if I can get a picture of it.

In the past I used a couple of "Y" connectors to connect both the sound system and the radio unit to the the RCA line outs, but had decided to try the 1/4" cable this year...maybe that was the problem. I didn't have my Y-adaptors with me that day so I couldn't fall back to the old way. The Cobra documentation says you can use both outputs at the same time.

audiobox.jpg

I don't think the 1/4" cable was the problem. In general, you should never "y" connect any audio input/output, balanced or unbalanced. (that 1/4' output is most likely directly tied to the RCA jacks, so electrically it is the same as a "Y" cable.) As Marcel illustrated, it is very easy to cause a ground loop, especially with gear you are not fully in control of or own. Also, some devises outputs especially don't like having another signal directly tied to them.

One thing you can try is use the stereo bus connection on the ZMX mixer, to feed the transmitter. IIRC the levels you set with the input controls (you should be using input 7 or 8) will affect that bus, I am not sure if the master controls do. I may have my setup out for testing soon and if I can, I will see if that is the case. The other and safest option (though it will be mono) is use the AUX OUT on the mixer to feed the transmitter.

As for the gain pots, see my other post above. You can go the the QSC parts site and get the correct part number for those amp you have, and changing them is pretty easy if you know how to solder (I would assume the tech you mentioned does.)

As suggested, a quick fix would be to open both amps, blow out any dust, and spray the pots with a good contact or pot cleaner.

[Mark Gulbrandsen]

No need for the XLR kit for your player, the stereo music inputs for the mixer (7 and 8) are unbalanced RCA. Don't waste the money on that kit.

Yes the cable to and from the mixer is 2 conductor shielded, Belden 8451 or equiv.

Yes, use the Left and right outputs to the inputs on the amps, use the screw terminals on the amps to save time and effort making up XLRs.

Speakons are the way to go with the speakers for sure. I even use them from the rack to the field wiring in permanent installs, to allow easy disconnect to protect the equipment from lightning. You can get premade 12ga Speakon cables online for reasonable cost, in lengths up to 200 feet. Amazon sells the connectors for your speakers and the rack cheap as well.

The connector panel I used was modified, I removed two of the XLRs to add the speakons. You will have to search for it to find a new vendor, MCM/Newark no longer shows it. It was made by Stellar Labs.

Check you messages on here, I will give you my contact info.

Tony,

I switched to using Mogami 2944 2 conductor shielded on my portable dailies gear years ago... the applications here are screaming for the stuff... I used it for all my interconnects from dubbers and projectors to the amp racks because it's actually intended to be an internal / external cable. It's extremely flexible compared to 8451, however, you could also try 9451, it strips much easier and is a little more flexible than the 8451, but not as durable or flexible as the Mogami. The Mogami stuff is just so nice to work with and the extra flexibility ads more built in safety for cabling going between a mixer and amp rack, or if gear should loosen up in a rack during transit. The flexibility ads assembly convenience as well. 8451 is really meant for permanently installed gear that's not going to be moved around, and I still wire stationary racks with it. Mogami is more expensive, but worth it! 200 meters, a little over 650 feet is about $170 USD. Performance Audio in Salt Lake Silly stocks just about all the Mogami stuff.

Next up... I will be waiting for the thread on how to get rid of the hum in Mike's new system... That should generate at least 5 pages of posts...

[Mike Blakesley]

Hey, if it gets results....

[Tony Bandiera Jr]

Hey, if it gets results....

Mike, spending extra on the mogami cable won't help you out here. I have used Belden by the hundreds of miles in installs and equipment for decades with ZERO issues, and West Penn cable makes Belden equivalents that are less expensive (but sometimes harder to strip, which is an initial install issue not a user issue.)

Nothing wrong with using more expensive cables of course (in some cases, a lot of "audiophile" cables are just snake oil.), but changing cable brands will NOT solve the problem you had. Mark is just talking to hear himself talk in this case. (And quoting a year old post where that ship has sailed already, lol.) BUT Mark has a point when it comes to the microphone cable used with XLR connectors..the Mogami is hands down the best and most durable cable.

Save the money and use it on more important things (like maybe finding a good transmitter that YOU own and control so you can test it thoroughly before the shows.) And invest in a few DI boxes and isolation transformers to have on hand in case someone wants to connect some oddball equipment to your system. Monoprice and BH Photo Video have many of those devices at good prices.

[Mike Blakesley]

Well the first thing I'm going to try is using a different cable with the transmitter and moving it to a different power source. If that doesn't work we might just forget about the radio thing because we really want people to come into the fairgrounds and see the show up close anyway, for the best experience. That part of it is about 5% of my concern.

If I'm making any improvements to the system, the next thing we might think about is replacing the speakers with newer/smaller units. The Cerwin Vegas are awesome sounding but one downside about them is, they have a pretty narrow dispersion field. If you're right in front of them they sound amazing, but get a little outside that narrow cone and the sound quality is markedly diminished.

When I was using those speakers as a mobile DJ, we loved them because we would put them on the four corners of the dancefloor. When you walked into that "box" created by the four speakers, the sound was just excellent. But if you went to where the seating areas etc. were, the sound was less intrusive. It was perfect.

They work less well in this outdoor environment because of the size of the field we're in. Until this year, we would line up the four speakers facing the crowd from the front. This year since we had the new system with the much-improved speaker cables, we tried to re-create the 'box' concept by putting two of of the speakers in front of the crowd and two on the sides about 100' back as indicated in my photo on page 1, but I think the area is just too big for that setup. It sounded fine in some places, but there were too many areas where it just didn't sound that great (especially if you were near the speaker with no tweeter). I'm thinking the four-across-the-front may be the way to go. More experimenting will be done next year. We would have had more time to fiddle with it this year except it was getting really hot outside, and there was a storm brewing, so we were more worried about getting everything set up and then covering it.

[Marcel Birgelen]

If you move the transmitter over to the same power source as the rack, the hum should be gone or greatly reduced. Either that, or the transmitter is a piece of trash that can best be ritually discarded.

Outdoor PA audio is a different beast than indoor audio. It's easy to underestimate the coverage area of an outdoor event compared to most indoor venues. You either need far more power or you need to concentrate that power more wisely. Yet, just adding raw power also often isn't the solution, especially if you're in an environment surrounded by buildings. Those people living in those buildings may not appreciate all the attention you're giving them and those same buildings may also cause some nasty reflections, causing all kinds of disturbing echo.

[Mike Blakesley]

Outdoor PA audio is a different beast than indoor audio.

Given the other fireworks shows I've attended, I'm probably giving more thought to the audio than it deserves. Some of the other shows either have no music, horrible music, or horrible sound, or both. However I do put a lot of work into our soundtracks (I edit 15 or 20 songs into a 19 minute show, as a rule) so I would like people to hear them as well as possible, but the fireworks going off in the background do make it a bit more difficult than a typical outdoor setting!

[Marcel Birgelen]

Given the other fireworks shows I've attended, I'm probably giving more thought to the audio than it deserves.

Being a sucker for good presentations, I love it when a good plan comes together... Using other's mediocre firework shows as benchmark shouldn't be your goal. For me, a good fireworks show gets immediately bumped up a notch or two with some good music in the background. That music doesn't need to be at concert level volumes.

Not to discourage your efforts, but this is how it looks when music, pyrotechnics, a bunch of drones, projection, water and a few million dollars down the rabbit hole come together: