newb wiring some sirens

I have a Compustsar P2wss-as with the P2WSSR remote which utilizes the CM400 brain. As far as I know I can use the modules siren output to power a relay (pin 85) and connect my sirens that way. I have a backup battery and I read somewhere that the sirens would no longer work if the + is cut if I wire it this way. So is there any other way I can do this? I have 2 sirens and a Piezo. Car is a 95 Eclipse Gst. Thank you guys. On a side note I have it hooked up this way now and it does not work. 85 Signal 86 - 87 +12v 30 Output to sirens

Anyone? I live in a pretty bad area and I hate not having everything at 100%

Good idea but I already payed the money for the setup I have now can't afford that.

The way I hooked them up in my truck before was like this. Connect a positive lead to the main power lead to your alarm then to Pin 86, connect pin 85 to ground (this keeps the coil energized as long as the alarm has power). Connect pin 30 to your sirens Positive lead and connect pin 87a to a separate constant power source such as another battery etc. Its set up as a collapsible circuit once the your main battery cable is cut the power to the alarm will be interrupted and the relay will no longer have power to the coil closing the circuit between pins 87a and 30 setting off the back up sirens. This was a good setup for GM trucks where the positive battery cable is easily cut. A backup siren is easier and more fool proof. I am not sure how long the relay will last with the coil constantly powered. I sold my truck shortly after this alarm install. Diagram link

I'm going to try this out right now. Thanks I'll post back on how it works.