What is the most cost efficient way to build a mobile sound system for portable parties?

How are you going to power it? Long extension leads or batteries. Power out needs power in – not much battery life.

want batteries, but it will probably have to be extension chords for weight and power consumption reasons

You are going to need a set of commercial speakers in durable boxes and an amp. Try eBay, Craigs List etc, they are pretty pricey new.

estimates of cost? weight? quality?

@pikipubiba, you can find an estimate of cost by going onto ebay, finding what you need, and getting the cost and weight yourself. As for the quality, you will probably have to take the time to go to Best Buy, several stereo stores, etc. and listen to judge the sound of the equipment yourself. You’re the one starting the business, not @DarkScribe. You need to do your own homework.

You will need to check with city government to see if you are going to need a permit for gatherings, and you will need to check to see if there are any noise ordinances that you will be violating, etc.. Checking into things like this before you start a business is a good idea.

This sounds like a fun idea, BTW.

@PandoraBoxx Oh, don’t worry, I’m covering all my bases, I just know that fluther has a history of pooping awesomeness, so this is kind of a check on the research I am doing.

We already did this once with a 75 watt system and it was sweet, so we are trying to ramp it up and get funding.

Sounds like a Bose L1 would be a good fit for you. They are light weight, assembly is quick and easy, and they are compact and transport well. I’ve seen one of these handle a room with several hundred people with no problem.