Stereo To Mono with SINGLE Powered Speaker

I have a powered speaker (Behringer B215D). What is the best way to plug an iPod into ONE SPEAKER?

Here is the I/O diagram: http://www.behringer.com/assets/B208...5D_fig1_XL.png

Is there anyway to preserve the stereo signal from the iPod?

Will a 3.5mm to 1/4 inch TRS adapter carry the left and right stereo channels to the speaker?

Thanks.