Xtant DVC 4 ohm Woofers/RF 501s amp

I have an Xtant Dual Voice Coil 4ohm Woofer Rated at 500w RMS and a 2 channel Rockford Fosgate 501s amp rated at 100w X 2 @ 4ohm, 250w X 2  @ 2ohm,or 500w X 1 @ 4 ohm. In order to wire these up (let me know if im wrong) is to wire in parallel with only one of the voice coil and that will put out 4 ohms. They Sound okay, but at higher gains levels they seem to make a weird noise as if something is rubbed on it, lets say if you put a pencil on the woofer when its running. I thought it was the letters on the woofer but it wasnt. Would that be a possible distortion?

I had them running  into a different amp. A 2 channel Logic amp rated at 150w X 2 @ 2ohms, or 300w X 1 @ 1ohm bridged. I had the subs wired parallel using both coils so it would put out a 2 ohm load. When i wired them up with this amp, the sub wasnt making that noise and it pounded sooo much harder. I loved it. Why isnt the rockford fosgate amp doing that when it seem to all match up? Could it be the amp? why is this 300w amp hitting my subs harder than the 500w rockford fosgate? Does the Impendence have alot to do with it? As you can see, im a newbie and a detailed description would be appreciative.

Its out of phase, you need to run them in bridged mode.

This would series / parallel

Thats what I was thinking, ignore basically everything up above. Your amp is stable to a 4 ohm mono load only. While it can and will run a 2 ohm mono load, it will do it for a finite period. Meaning it will go into thermal protection real damn quick. I do not recommend it at all. You can continue to operate the sub with one coil only or a better idea would be to wire the sub in series to 8 ohms, whle this may lower the overall output level of the amp, it is the safest way to operate this sub on this amp. A dedicted mono sub amp that is stable to either 1 or 2 ohms is in your future if this combination will not do what you need it to. A thing to remember here is that most if not all Rockford amplifiers will happily exceed their rated power ratings, especially in bridged mono. I bet that this sub will pound away quite well. Here is how to wire the sub properly.

Wiring Option #2

Like I said, the Rockford amp is underrated, run it in this fashion for the best performance, your sub is rated if I remember correct at 500w rms, split 250w rms per coil. So over 500 w rms into one coil could result in sss due to excessive heat transfer. Wire it in 8 ohms and play it safe.

Like Rob is telling you, you can't.  A DVC 4-ohm sub can be wired for 8-ohms or for 2-ohms.  You cannot wire it for 4-ohms.

couldnt i wire just a single connection? I thought DVC just leaves you with more wiring options. If i only wire up one of the connection from the woofer, i wouldnt be using all of the coils? im a newbie as you can see. just really curious. I thought it was okay to connect only one of the connections. If i used up only one of the connections and wire them parallel, It will put out a 4 ohm load. wouldnt it?