Do any of the Ottawa area users know where I can find 1/4" MDF in the Ottawa area? Home Depot doesn't carry it that small...let me know...thanks...

 

If you're having a hard time finding 1/4" MDF just use 1/4" tempered masonite also known as hardboard. Just make sure it is tempered...usually a darker brown colour versis the regular masonite, which is pretty light in colour.
Should work fine for mounting speakers...if that's what you're using it for. The tempered is just as rigid as MDF, just not as heavy. Hope this helps.