Pre-Wire External Sounder Location

[LarrylLix]

Why not just leave the horn where the professional installers put it and it functions best, as designed?
 
Every installation company here installs them in the ductwork due to the superb function of the sound. It is best to have a dead air pocket, though, to avoid dust buildup.
 
The location also makes the unit hard to access if somebody wanted to preset your home for a break-in.

 

[Del91574]

And just because "every installation company here" puts them there, that doesn't make it right, compliant, or a good idea. NFPA 262 and NFPA 90A address plenum and cabling and NFPA 255 covers testing of these devices.(and now you diverge into the tangent of how Canada doesn't recognize US' NFPA.....) I doubt the $20 siren that is being installed by the trunkslammers (hardly professional) in your area has the applicable ratings or listings. Maybe we're also talking a sub $100 DSC install as commonplace as well, so $20 on a $100 panel, keypad, PIR and battery package is going to break the bank.
 
Here are some links to some light reading for you Larry, as I am slightly disappointed that someone, even an avid hobbyist would suggest an inherently bad and dangerous practice, no matter who does it. The fact that others in your locale are not being called out on it by the AHJ or building officials speak volumes about the quality of work being enforced. IBC and IRC both cover the standards. Jeopardizing safety to save money on an install is a poor practice to get into. Far easier to either move from a siren to an appropriate number of speakers and related driver, or to install the proper devices and quantity to begin with. 
 
I apologize for not snipping the links in advance
 
http://www.extron.com/company/article.aspx?id=plenumrated_ts
 
http://ecmweb.com/low-voltagecommunications/what-lurks-ceiling
 
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CDQQFjADahUKEwiLxvDOw6vHAhUEyT4KHaw6Dsw&url=http%3A%2F%2Ful.com%2Fwp-content%2Fuploads%2F2014%2F04%2Ful_PlenumsProductsUsedIn.pdf&ei=fGvPVYuYHYSS-wGs9bjgDA&usg=AFQjCNHkmPZBriXiZqDWnWScR_GGoYtp-w&bvm=bv.99804247,d.cWw&cad=rja
 
https://sewelldirect.com/learning-center/Plenum-Space
 
I'm sorry Larry, but you're wrong, the parties you reference are in the wrong and your suggestions are inherently dangerous.