Upgrade your dorm to a certain point and you'll start earning more speakers per day. It's like another 5 per day from being in a club too, I think.
Speakers regain once every 24 hours. You can be patient and wait, or you can buy speakers from the store for a cost of extra credits. You can earn extra credits by doing jobs, which has a 2% drop rate, or you can buy extra credits from the nurse using real money. The nurse can be found by going to the store, or clicking on your ATM.