I am in the process of building a DBII for my two 12" Rockford subs.  I want to run them Isobaric (clamshell).  I understand that they need to be run 180 degrees out of phase.  

The subs are dual voice coil subs that I would like to run  combined at 1 ohm.  

Is it possible to do this off of 1 mono amplifier, and if so could someone help me out with how to wire it?

Any help would be greatly appreciated

Thanks

So, you have 4 - 4 ohm voice coils? To get a 1 ohm load they would all be in parallel. To clamshell, both voice coils on one driver will be reverse phased, but still parallel.

[quote author=REDTHUNDER  link=1142979181/0#3 date=1142977867]...  So if I follow the chart then my amp will be runnning at 1 ohm and the subs will be out of phase?  By the way if my subs can handle 400W RMS each, how much power should I be running to them in this configuration.  My understanding is that they need more power running this way.
[/quote]

The chart is correct for 1 ohm hook-up, clamshell. Just be careful using "out of phase" as an expression, because the drivers are out of phase ELECTRICALLY, but you are correcting that condition MECHANICALLY by turning one around and facing them together. In a clamshell arrangement the drivers have to work together as one unit. The only way to do that is to wire one of them electrically out of phase with the other.

I'm in danger of sounding like I'm nitpicking your semantics, but your drivers can't take much more power than their rating, although they do support each other against over excursion to some degree. If you read about needing more power in a clamshell arrangement, it's true, because by facing the drivers together, you have reduced your diaphram radiating area by half and lost 3dB of output as a result. So to get back to the same output in dB you need to double the power, but don't go too crazy and overpower your drivers. If your drivers are overpowered to the point of failure, it will most likely be heat that causes the failure in a clamshell loading.

2 subs in clamshell @ 800wrms (400 each) means you have the same spl as 1 sub @ 400wrms

well, if you have 3 subs in a box, you need to run 1200wrms to the box if each sub is 400wrms.
same goes to isobaric.
add the rms of each sub and that is the rms of the 'group'.

i was thinking about identical subs. forgot to mention that.
i still can't get it : how does wiring (series/parralel) affect the power distribution between 2 or 3 any amount of speakers ?

it's actually very good if you have 1400w rms available, because you have headroom. try to adjust the gain so that the amp puts out 800w rms at about 75% volume on the HU