Sound system protection ?'s

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SmithBuilt

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My church has had a part of the sound system knocked out by lighting. The sound guy says it came from the microphone wiring into the dbx controller, not from the electrical system. I have a hard time believing that, but really don't know.

The sound man wants us to put a ground rod close to the system and connect it with #6 solid to the chassis. I don't think this will do much if anything. Steel framed building.

Any thoughts on protecting this equipment? We do not have any protection at the service just the surge protection strips at the equipment.

Thanks,
Tim
 
First off, a ground rod isn't going to help and will most likely be a Code violation.

Is the rack itself already grounded? Common practice for my work with cinemas and home screening rooms is a minimum #8 (usually #6) insulated ground from the panel's ground bus to the rack itself, in addition to the EGC's for the serving circuits.

Perhaps bonding the rack to the building steel, if it is already bonded to the GE system, might help. But I would ensure the ground wire I mentioned is installed, it would work better in most cases.

What proof does he have that it came in from the mic wiring? What exactly was damaged? Did he find any damage to any cabling where the lightning might have arced from nearby conductors or building steel? In any event I am not aware of any surge protection devices for audio lines. (Not to say they don't exist, just haven't heard of them.)

You would be well served to install a surge protection system at the main panel of the building AND at the subpanel serving the sound system if one is present.

Surge protection MUST be multi-layered to be effective. At the panel and at each point of use is a bare minimum. And use quality surge strips, not the big box/bargain store specials.

There was one case a long time ago of a home recording studio where the house took a direct lightning hit...the owner had the multi-layers of protection in place (main, sub panel for studio, and all electronics throughout the house). NONE of the studio gear or individual surge protectors was damaged, the sub panel surge protector was sacrificed on one leg, the main surge protector was blown out on both legs...and only the surge strips on some of the other electronics throughout the rest of the house were dead. Only some clocks and lights were blown out. All were high-quality devices (IIRC it was Tripp-lite on the main and sub, a mix of APC and Tripp=lite on the strips. This was back in the 80's though, so my memory of brands may be a bit off.)
 
mxslick said:
What proof does he have that it came in from the mic wiring? What exactly was damaged? Did he find any damage to any cabling where the lightning might have arced from nearby conductors or building steel? In any event I am not aware of any surge protection devices for audio lines. (Not to say they don't exist, just haven't heard of them.)
Click to expand...

No proof. DBX controller, I assume a zone controller, I'm not an audio pro, but all the mics and speakers connect to this and then it is connected to a mixer. He provided no proof, no arced wiring.
 
Then in that case it would be difficult to point at the mic cabling as the source of the trouble. It is even possible that the dbx unit had a failing power supply and the surge from the lightning pushed it over the edge. Nothing to do with a surge entering the mic lines.

Best bet is as I suggested above, ground the rack itself with #6 back to panel ground bus, install TVSS at main and subpanels, and replace all existing surge strips with new ones by a quality maker. (I forgot to mention in the previous post that the existing strips are most likely not working anymore on the protection side..they may have even been compromised before this event from prior surges.)
 
Not sure of the distances etc.

But bigger is generally better with the conductor, keep the conductor as straight as possible (no tight bends), clean the paint off the rack, TVSS at the sound equipment, outlet for the sound equipment and at the panel and sub panel if one is involved.
 
This is the product that most pros recommend for protection

I have no affiliation



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I spent a few days this spring helping put a radio station in northern Missouri back together after a lightning strike which hit next door.

No power supplies were blown on anything (critical gear is on APC UPS's and the panel has a TVSS). As far as we could tell, all damage seems to have been caused by the EM pulse generated by the strike being induced into the LAN, telco and audio cables, including shielded cables.

Every connected Ethernet port on two different network switches were blown, along with Ethernet ports on all computers in the building. Also, all of the Meridian phones were blown except one with a 6-foot run between the phone and the KSU (which was undamaged). Most of the input and output IC chips on the audio consoles were blown as well.

Made a lot of money cleaning that up...:roll:
 
As far as we could tell, all damage seems to have been caused by the EM pulse generated by the strike being induced into the LAN, telco and audio cables, including shielded cables... Every connected Ethernet port on two different network switches were blown, along with Ethernet ports on all computers in the building. Also, all of the Meridian phones were blown except one with a 6-foot run between the phone and the KSU (which was undamaged).

I've seen that also at my own office. Close strike wiped out the ethernet port on my network printer but the switch port at the other end was undamaged. On the other hand it took out an extension port on the phone system KSU but the connected phone was untouched. There is really no way to protect against this kind of thing.

-Hal
 
grich said:
I spent a few days this spring helping put a radio station in northern Missouri back together after a lightning strike which hit next door.

No power supplies were blown on anything (critical gear is on APC UPS's and the panel has a TVSS). As far as we could tell, all damage seems to have been caused by the EM pulse generated by the strike being induced into the LAN, telco and audio cables, including shielded cables.

Every connected Ethernet port on two different network switches were blown, along with Ethernet ports on all computers in the building. Also, all of the Meridian phones were blown except one with a 6-foot run between the phone and the KSU (which was undamaged). Most of the input and output IC chips on the audio consoles were blown as well.

Made a lot of money cleaning that up...:roll:
Click to expand...

And this is the reason a church audio system is very hard to protect after it has been installed, wire runs (audio, Speaker, Etc..) are crucial to limiting the magnetic impulse of a near field strike, the problem is two fold, one is the current induced on the conductors act like the secondary of a transformer, no longer with a reference to Earth, so common mode TVSS devices wont protect the equipment, second this current will form on all the conductors in a cable like the whole cable is just one wire of a circuit, this leaves TVSS between each conductors within that cable with no clamping ability because it is clamping the same conductor, the biggest problem is most of the time these conductor runs are ran separately each taking there own pathway through the building and this greatly enhances the ability of current from a near field lightning strike to be induced on them, the trick when installing everything in the beginning is to try to keep as much as passable all the runs together except where you need to branch out to go to each device, this is one of the main reasons when you see the conductors coming in from a radio tower they are all ran together in a tray into the building through a single point that has a ground ring around this point, this causes all the conductors to act like a single pathway in a circuit and prevents current to flow from near field strikes.

Lightning is a high frequency event that follows the RF theory for the most part.

I have studied many of these type of strikes, and in every case the destroyed equipment had two or more conductive paths from it ran apart from each other, the one that jumped out at me was a home entertainment system, it had a sub woofer on another wall fed from a different circuit ran in a different path back to the main panel, the audio cable between the main amp and this self amplified sub was burnt into the carpet all the way around the room, and could have easily caught anything on fire if it was ran over paper, luckily the carpet was flame retardant.

Oh and DBX is a brand name who make all kinds of audio equipment for PA systems, more commonly known for their compression limiters, and 1/3rd octave EQ's, but I believe the OP is talking about a breakout box, that is also called a multi-tap DI box, used to send inputs from mic's, guitars, and other DI'ed instruments. (DI=direct in) as opposed to miked in.
 
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