Streetfest setup

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BJ James

Junior
Jan 11, 2011
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I have a job coming up where they are having competitive rowboat races and want speakers (around a dozen) setup along a parrallel street for a distance of about 800'. It is mainly for announcements, and play by play of the races, but also to play canned music and a couple acoustic style musical numbers that they want sent out through the whole area. The usual 70v horns aren't going to cut it for this, so I was thinking of using a bunch of our 12" and 15" fullrange passive boxes and buy a bunch of 100w 70v transformers for them. I have a spare PL340 that is capable of driving 70v without a step up transformer, add a small mixer and I'm good to go. I have a pile of 12 and 14g speaker cable.
Assuming this all sounds reasonable, they also want the program material to be played though the concert PA during certain times. We are also supplying a system for live entertainment throughout the day. The mixers an these 2 systems will be about 800' from each other. I was just going to run a balanced line from one mixer to the other. Since they are on 2 different electrical services, will I need an XLR iso transformer? I ask, because the distributed system will be plugged into a GFCI and I recall haviing problems in the past when encountering these.
Thanks,
BJ
 
Re: Streetfest setup

I do stuff like this all the time. The results my clients want, and the obstacles presented by the sites require extensive crew and planning. What's the budget?
 
Re: Streetfest setup

Yes, I agree. Budget is appropriate for the planning and crew needed. But that's not the issue at hand.
 
Re: Streetfest setup

Depending on the proximity of the listeners and the desired depth of coverage, I've tended to put the speakers in splayed pairs every 100'. Nice, even coverage and somewhat of a consolidation of resources. A pair of 90 degree boxes at that spacing gives a pretty nice sound field.

Another fellow I know who does several Dragon Boat races has bought a few of the cheapo 1KW gas generators (I believe they have inverter technology) and puts one with every pair of powered speakers.
 
Re: Streetfest setup

Is any part of the 70V system closer to the concert system? You can tap into that 70V speaker feed using a spare 70V speaker transformer and knock that 8 Ohm speaker level down to line level with a pad (or knock it to mic level with a passive DI that accepts speaker level input). The transformers take care of your isolation worries, and there is no ground to worry about.

I've done this on a few occasions for various reasons, and it always works well.
 
Re: Streetfest setup

Milt Hathaway said:
Is any part of the 70V system closer to the concert system? You can tap into that 70V speaker feed using a spare 70V speaker transformer and knock that 8 Ohm speaker level down to line level with a pad (or knock it to mic level with a passive DI that accepts speaker level input). The transformers take care of your isolation worries, and there is no ground to worry about.

I've done this on a few occasions for various reasons, and it always works well.
Click to expand...

I'd say he could go straight into the DI without a transformer first. The high input impedance of the DI is not going to affect the 70V system at all.
 
Re: Streetfest setup

Milt Hathaway said:
It shouldn't, but I prefer that extra bit of isolation too.
Click to expand...

Wouldn't a passive DI have a transformer in it anyway? I'm definitely a fan of overkill though, so maybe we should use a couple DIs :)

I was originally against using the 70 volt to 8 ohm transformer because they saturate way too easily. Thinking about it, though, with no real current being drawn through it (high impedance load), it probably wouldn't. I'm no expert on transformers though.
 
Re: Streetfest setup

Silas Pradetto said:
Wouldn't a passive DI have a transformer in it anyway? I'm definitely a fan of overkill though, so maybe we should use a couple DIs :)

I was originally against using the 70 volt to 8 ohm transformer because they saturate way too easily. Thinking about it, though, with no real current being drawn through it (high impedance load), it probably wouldn't. I'm no expert on transformers though.
Click to expand...

It's the same type transformer feeding everything else on the 70V system.

Another reason I prefer to include it is my hesitance to feed high voltages to a device that wasn't really designed for it.
 
Re: Streetfest setup

I do a very similar setup every year. About 1000'- 1200' of coverage needed. This year we had about 35-40K people in attendence. It takes more than a dozen speakers to do it right.

I use 90 degree powered boxes, two per location about 13'-15' in the air. I also have one area where I need more balls so I use some large tap boxes.

We use a 45kVa generator and run power to all the locations. I used to use separate small generators but when you do these right you don't have much current draw and the voltage drop at the end of 400' of power cable is not an issue.

We have done wireless before but there is nothing like a couple pirates battling over their own little place on earth. This has happened to us. We got hammered by a mexican pirate radio station that wasn't there the night before when doing our testing. So it is all wired now. Takes a lot longer to set up but no need to worry.

As far as using an ISO transformer if on different circuits....Do it! I carry a bunch and when we used to use small generators we put an ISO for each gen set.
 
Re: Streetfest setup

BJ James said:
I have a job coming up where they are having competitive rowboat races and want speakers (around a dozen) setup along a parrallel street for a distance of about 800'. It is mainly for announcements, and play by play of the races, but also to play canned music and a couple acoustic style musical numbers that they want sent out through the whole area. The usual 70v horns aren't going to cut it for this, so I was thinking of using a bunch of our 12" and 15" fullrange passive boxes and buy a bunch of 100w 70v transformers for them. I have a spare PL340 that is capable of driving 70v without a step up transformer, add a small mixer and I'm good to go. I have a pile of 12 and 14g speaker cable.
Assuming this all sounds reasonable, they also want the program material to be played though the concert PA during certain times. We are also supplying a system for live entertainment throughout the day. The mixers an these 2 systems will be about 800' from each other. I was just going to run a balanced line from one mixer to the other. Since they are on 2 different electrical services, will I need an XLR iso transformer? I ask, because the distributed system will be plugged into a GFCI and I recall haviing problems in the past when encountering these.
Thanks,
BJ
Click to expand...

James.

I haven't done exactly what you propose, but I just had a gig where I took some photos that might initerest or inspire you :)

Basically it's a youths' soccer event with 1500 participants + audience that spans over 4 soccer fields. They want to be able to make announcements and commentaries and this is a quick breakdown of our solution:

Wireless receiver with paddle antennaes as well as playback sources and some 58s on stage. They are connected to a Yamaha 01v96 routed to make 3 mono mixes and one stereo. A custom layer is configured so that there is a master fader for each mix. Three mixes are routed to the surrounding areas whereas the stereo mix feeds two stacks of PA on stage to cober the area in front of it for prize ceremonies.

The three mono mixes go from the 01v96 through a 50 meter EWI multicore to an Allen & Heath MixWiz 16:2 where the main outs and some of the AUXs are used to distribute the various zones to various lines and wireless transmitters running from that one centralized location.

Where we can safely lay wire we do so, where we can't we use wireless. By transmitting on several frequencies we can just "tune" the speakers to the zone we want for that location 8)~:cool:~:cool:

By conicinence, the places where we would have had ground loop issues is where we intended to use wireless, anyways. Lucky for once! Iso transformers would have been the way to go, otherwise. For really long runs, running a 70 volt amp and getting one of those 70v-to-lineout- boxes on the end is a great solution.

The announcer could stroll all over the area with his handheld mic if he wanted but it took some heavy concentration in some areas as the delay of sound propragation was pretty severe is some parts of the venue.

I run a small company so we had to get a little creative to manage all the long lines, but using DMX and various snakes got us there with cable left over for all other projects that weekend. If we land more gigs like these I'll be investing into more long single lines on reels.

Here are the small speakers on sticks (16 total):
http://hkaudio.com/products.php5?section=ps&id=11&prod=D.A.R.T

Here is the PA on stage:
http://hkaudio.com/products.php5?section=ps&id=10&prod=PROJECTOR
 

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