Dual Voice Coil Subs?

[Bobbler]

Ok. now after playing about with car audio for some time, I have decided that I am going to get a new sub to replace my ageing JBL which is honestly a bit worse for wear now and really lacks the sort of control I like in my current music tastes.
I am looking at getting a new amp to drive it which is the Alpine MRV F345 to replace my Vibe VP2 and BB1 (hopefully shave a little off the cars weight too in the process LOL)
I am configuring it to stick one pair of channels to some components up front and bridge the second channel to run the sub. This bridged output is at 4ohms. Now what I need some help with is picking from either a dual 2ohm sub or a dual 4ohm sub to connect up to the amplifier, which do I need to buy? How do I connect it up to show the correct loading to the amp?
I have read some of the FAQS on TA forums but they dont really cover this situation, only running two channels to the sub or running it from a 2ohm source.
Any of the ICE bods help out a "intermidiate" noob?

 

[andi]

Have a read of this about wiring up dual voice coil subs on the JL website and see if it helps..

http://mobile.jlaudio.com/support_pages.php?page_id=161

I think (it's late..) you want a dual 2Ohm wired in series if your source is 4Ohm.

The other tutorials on the JL site are a handy read too..

http://mobile.jlaudio.com/support_pages.php?page_id=127

 

[Bobbler]

Cheers Andi, that sorted it out for me, a dual 2ohm in series is the right one from that info.

 

[Jonny69]

Yup, two 2 Ohm coils in series makes 4 Ohms, two 2 Ohm coild in parallel makes 1 Ohm.

Same goes for 4 and 8 Ohm coils. Just make sure the speaker impedance isn't lower than the amp is designed to put out or it will draw too much current and overheat the amp. If the impedance is too high then you won't damage anything, you just won't be able to get the full power out the amp.