Does it matter which kind you use for a sub? I just bought the Dayton SUB-100, and I plan on hooking it up to my Onkyo TX-SR304.

The 304 has a subwoofer Preout. How do I connect the sub to it?

This is the back of the sub
http://img301.imageshack.us/img301/3710/300633ivjm1.jpg

This is the back of the 304
http://img239.imageshack.us/img239/4048/receiverwn7.jpg

Sub Preout on the receiver to one of the Line In RCA jacks on the sub, most people use the left one but it should not matter for the mono signal.

For the sub you want to use a coax cable with RCA ends, often referred as coax digital cable.

Why would it matter that the cable is listed as a coax digital cable as the signal is analog?

"Coax digital" is essentially an overpriced composite video cable. In your case just use the regular "audio" cable with RCA terminations.

For the sub you want to use a coax cable with RCA ends, often referred as coax digital cable.

I think it would more often be referred to as a 75 ohm unbalanced or RCA cable. Coax digital is a "special" type of that cable just for the 0s and 1s of digital audio, such as for DTS or dolby digital transmission. Since a subwoofer receives analog instead of digital audio, I don't see a need for the digital coax, even if there really was a difference between one RCA cable and another for all practical purposes in the typical consumer's price range.

I think it would more often be referred to as a 75 ohm unbalanced or RCA cable. Coax digital is a "special" type of that cable just for the 0s and 1s of digital audio, such as for DTS or dolby digital transmission. Since a subwoofer receives analog instead of digital audio, I don't see a need for the digital coax, even if there really was a difference between one RCA cable and another for all practical purposes in the typical consumer's price range.

The cables are typically the same. Very few manufacturers use anything other than single-conductor foil-wrapped coax for everything. Premium analog cables might use stranded wire but that shouldn't be necessary for a subwoofer cable with low frequency signals that travel inside the wire rather than on the surface. The 75 Ohm impedance is irrelevant for audio connections whereas capacitance is critical, yet rarely reported.