Connecting your iPhone or iPad (or any other device with a 3.5mm headphone jack for that matter) to your speakers system is a matter of what types of inputs your speaker system can take. If you’ve got a home theater setup with a receiver that can support RCA audio, then you simply need a 3.5mm to RCA adapter to get the job done. With that adapter you would plug in the 3.5mm side into your headphone jack and the RCA Left/Right audio side into RCA ports on your receiver or speaker system.
Some speakers only accept 3.5mm connectors as inputs. In that case a simple male-to-male 3.5mm to 3.5mm cable would work for you. Also known as stereo cables, in this setup you would plug one male 3.5mm connector into the iPhone and the other end into your speakers or compatible receiver.
One final option if you’re looking to buy speakers for your iPhone would be to go with standard computer speakers with 3.5mm connectors built in. Your iPhone uses the same connector style as a computer sound card so almost every pc speakers set will plug right into your iPhone.
Be sure to also checkout OutletPC’s selection of mini portable speakers which are great for taking on the road with your phone or tablet.