Bought a horn (speaker) for $20.00, and hooked it up to an old "boom box" I had. Only problem with the "boom box" is that all it has is an external plug-in is for headphones, not speakers. A headphone plug-in restricts the amount of volume (because it is for headphones) and I could get very little volume. Went down to my friendly neighborhgood pawn shop and four and AM/FM stereo/cassette player that also runs on 6 "D" cell batteries and it has plug-ins for the speakers. Bought it for $25.00 and it sounds as good as anyting I have heard. It is one of those little "cube" type stereos you see at discount houses for around $100.00 all the time and it and the horn will fit in a day-pack.. At $100, it is not any more attractive than what you can buy already rigged up for predator calling in that you have to buy a horn also, however, at the price you can pick one up for in a pawn shop, it makes this quite a viable option. For less than $50.00 (I already had the speaker wire), I have an electronic game call. Used it today for the 1st time. Didn't call up any critters (but didn't really expect to at high noon) but the "field test" went well. It is a very economical alternative.